AD-778 380

TRANSACTIONS. TECHNICAL OPERATIONS OFTHE MARITIME FLEET. THERMOCHEMICALSTUDIES. CONTROL OF CORROSION ANDFOULING. CENTRAL SCIENTIFIC RESEARCHINSTITUTE OF THE MARITIME FLEETNUMBER 160, 1972

Naval Intelligence Support CenterWashington, D. C.

12 February 1974

DISTRIBUTED BY:

National Technical Information ServiceU. S. DEPARTMENT OF COMMERCE5285 Port Royal Road, Springfield Va. 22151

0 <~O~f\DEPARTMENT THlE NAVY___ ~ ji~ NAVAL INTELLIGENCE SUPPORT CENTER

00 TRANSLATION DIVISION4301 SUITLAND ROAD

op , WASHINGTON, D.C. 20390

C (LASSIF ICATION: UNCLASSIFIED

APPROVED FOR PU9LIC RELEASE, DISTRIBUTION UNLIMITED

TITLE: Transactions. Technical Operations of the Maritime

Fleet. Thermoch2mical Studies. Control of Corrosion

and Fouling. Central Scientifiz Research Institute

of the Maritime Fleet No. 160, 1972.

See Table of Contents.

AIJ7IJR (S): Various

PAGES: 61

SOURCE: Transactions. Technical Operations of the Maritime

Fleet. Thermochemica1 Studies. Control of Corrosion

and Fouling. Central Scientific Research Institute

of the Maritime Fleet No. 160, 1972.

Pp. 17-26, 26-30, 30-38, 38-46, 68-72, 72-78, and 89-93.

ORIGINAL LANGUAGE: Russian

TRANSLATOR: LD

NISC TRANSLATION No. 3514 APPROVED -

DATE 12 Fghruary 1974

VA

'Iransactions. rechnical Operations of thp, MaritimeFleet. Thermochiemical Studies. Control of Corrosionand Fouling. C, ntral Scientific Research Instlitteof the Maritime Fleet No. 160, 1972.

Table of Contents

PageReducing the Cure Time of the Last Coat of Antifouling Paintbyv Yti.Ye. Zabachev and S.T. Tsodikova.............................. I

Procedure of Determining the Adhesion of ThermoplasticCoatings by G.I. Shcherbinina and Yv.M. Kaplin ................... 14

Operating Tests of the Cathodic Protection System "Luga" onthe Motor Ship KAPITAN PLAUSHEVSKIY by A.A. Kysotski-y.............20

Effectiveness of Electrochemical Prutection of 25L SteelAgainst Corrosion Cavitation in Flowing Sea Water by G.K.Gavrskly, N.I. Yermolenko, Yu.Ye. Zobachev, A.V. Kurdin,Yii.V. Ltuk'yanova, and R.N. Metel'skaya ........................... 29

Distribution 3f Nigh-Frequency Vibration in Hulls ofKrasnograd-Class Ships Equipped with Ultrasonic AntifoulingProtection Systems by P.S. Sheherbakov, F. Ye. Grigor'yan,and N.V. Pogrebnyak .............................................. 39

Study of the Voltaic Couple Hull-Propeller by O.V.Yevdokimov and P.S. Shcherbakov .................................. 45

Methods of Accelerated Corrosion Testing of OrganosiliconCoatings by M.Ya. Rozenblyum and L.A. Suprun ..................... 56

REDUCING [HF CURE TiME OF TIHE LAST COAT OFANTIFOULING PAINT

iYu. Ye. Zobachuv (Candidate of Technical Sciences) ands. T. Tsodikova. TRANSACTIONS. Technical uperatlonsof the Maritime Fleet. Thermochemical Studies. Controlof Corrosion and Fouling. Central Scientific ResearchInstitute of the Maritime Fleet No. 160, 1072, pp. 17-26,Russian]

KhV-53 vinyl-base paint is now extensively used forprotecting underwater hull areas against fouling. Accord-ing to prevailing recommendations, the paint may be usedo,i r a fairly wide temperature range using the followingcure periods (after applying the entire coating): 24 hoursat temperatures above +15'C; 72 hours at 0 to +150 C; 120hours -- from 0 to -100 C; 144 hours -- below -10*C.

The shortage of dock time sometimes compels the ship-yard to violate these norms. According to foreign data (11,vin9i paint coatings do not require protracted curing priorto launching the ship. The Japanese firm "Tyupoku" suggests2-3 d..ys of ship dock time as adequate for painting theentire underwater hull area. There is no provision foradditional cure time before launching the ship [2]. On theother hand, conditions for paint-and-varnish film formationaffect considerably both the durability and protectiveproperties of coatings [3,4).

The service properties of antifouling paints alsodepend on the drying conditions. Thus, the protectiveproperties of incompletely dry vinyl paints may deterior-ate (9] and cause cold running of the paint on a ship inmotion [101.

The authors investigated the possibility of reducingthe cure time of the antifouling paint KhV-53 (beforelaunching) at various temperatures (including those in thewinter).

The study included the phyqico-chemical characteristics,the duration of drying and reaching full hardrnss as afunction of time and temperatures, the effects of differentdrying conditions on the antifouling properties of coatings,and the resistance of the coatings dried under variousconditions to washout and cold running.

Along with the antifouling paint KhV-53, tests werealso conducted on the regular anticorrosive ethynol-base

. . ..... .li I ~~~~~] i i i i i l i - lnl, ...

i iunderwater hull paint EKZhS-40. The drying time forreaching full hardness was in this case rated according toO)ST (All-Lniuon Standard) 10086-39 MI.17; the hardness wasritt,'d by COST (State Standard) 5233-50.

*h,. ant ifoitlin ability of the coating was determinedb%, in acc (orat(.d fl ycine method 1101. The test- s verecondictutd using the -quipment of the Leningrad Rranch ofth. State Research End Planning Institute and LeningradShipbuilding ln.;itu._,. Films of antifouling paint wereleached in glyc no, solutions (naCl, NaOlJ and amino aceticacid-glycine) for 3 days to approximate one year ofoperating a vessel in sea water.

The resistance of coatings to cold running was testedon a spindle machine [10] by rotating a painted disc(300-320mm in diameter) at 1050 rpm. A rough estimate ofthe friction resistance coefficient has shown that testsof coatings on discs are more rigid than on hulls of shipsin actual operation.

The specimens were dried at 20, 10, 0, -5, and -10'Cand were cured for 1, 2, 3, 4, and 5 days. The 10, 0, and-5'C temperatures were produced in a cooling chamber with85-90% air hu.nidity and limited air mobility., It wasshown in study [11] that the drying time of a paint-and-varnish coating markedly increases with an increase in airhumidity, beginning with 70%, and a decrease in air ex-change rate. Thus, the conditions of film formation inthe cooling chamber were more rigid than during paintingin open air in the docks.

The time of reaching the state of full dryness ofKhV-53 and EKZhS-40 paints is indicative of the solventevaporation rate from the coating permitting determinationof recoating time. Table 1 presents data indicating thefull drying time of the tests pzints.

After the solvent has evaporated from the paint, thefilm-forming processes continue for some time dependingon the type of the binder. Converted polymers undergochemical changes. The structural changes occurring inthe unconverted polymers include shrinking of moleculesto form sapermolecular structural elements. In bothcases, the entire set of physico-chemical properties ofthe coating also undergoes changes during this period.The hardness kinetics of the film is one of the typicalindicators for the drying ability of the crating (FiguresI and 2).

2

TABLE1

Air Paint drying tiyne, hours

atrKhV-53 FKMh-4nature

05 10 1.5 2.0 0.5 1.0 ].5 2.0

_0 Not Not Not Dry Not Not Not Dry5U dry dry dry dry 1dry dry

10 Not Dry - - Not Dry -

10dry dry

20 Dry - - - Dry -

Figue 1. Effet o rn duainadtme treo thhardnss ofEK~hS4 pintc- ts

Fiur 1. Effunfcrn drtion and temperature ond drihetme

3

The hardness of the KhV-53 paint lay7er at -10, -5,and 00 C is very low (0.1-0.2) and remains constant for 18days. The hardness of the EKZhS-40 layer at the sametemperatures after 7 days is also low (0.2-0.3). Atabove-zero temperatures the hardness of the EKZhS-40 paintincreases at a greater rate than that of the KhV-53 paint.After 7 days at +20'C the ethynol-base paint reaches ahigh hardness value of 0.7. Such high hardness values aretypical of converted coatings. Ethynol lacquer is capab] !of converting by oxidative polymerization (using air oxygen)to an irreversible state even within 6-7 days [121. Thephysical and mechanical tests conducted here have thusdemonstrated that protracted curing of coatings on under-water hull portions in open air does not contributi. toimproving the service properties particularly at below-zerotemperatures so that the assumed extended cure periods areby no means justified.

Further tests involving the effect of various dryingconditions on the antifouling properties of the KhV-53 painthave demonstrated also the absence of deterioration of itsprotective properties. As may be seen from Table 2, theleaching rate of the toxines (couprous oxide) remainsconstant at all below-zero temperatures and is about

3.0 mg/cm2 .72 hours. The control specimens that were driedat room temperatures within 24 hours exhibited a leaching

2rate of 3.0 mg/cm .72 hours.

TAPLE 2

2Cure time in Leachinq rate, mg/cm .72 hours at variousopen air, days temperatures, 0C

-10 -5 0

1 3.02 3.36 2.2

2 2.97 2.92 2.21

3 2.79 3.08 2.96

4 2.98 - -

5 2.99 3.08 2.99

4

The test data on resistance of the coatings to coldrunning obtained on spindle machines are given in Table 3.To reduce the painting cycle, the discs were given a fewernumber of coats -- three of EKZhS-40 paint and one ofKhV-53. In this case the antifouling paint was applied toone-half of a disc. The drying time was evaluated fromthe half disc coated with the antifouling paint. The datain Table 3 provides drying times for the chart as a wholeincluding the cure time of the last coat of the anti-fouling paint KhV-53.

It appears that the resistance of the paint tocreeping depends not only on the curing of the last coatof the antifouling paint but also on the last coat of theanticorrosive paint. For example, there was hardly anycold running at -100 C by drying 'Lhe last coats of EKZhS-40and KhV-53 paints for 24 hours (specimen No. 13). Adecrease in the drying time of the last coats of EKZhS-40and KhV-53 to 15 hours impaired the coating quality(specimens Nos. 14 and 15). In this case creep wasobserved in the experimental speed range of 7-9 m/sec(about 14-18 knots). Similar regularities have been ob-served at other temperatures as well.

The tests results have shown a difference in thebehavior of EKZhS-40 paint when recoated with antifouiingpaint and without it. On the chart with antifoulingpaint creen was observed to a lesser degree or was non-existent at all. Cold running is still evident on speci-mens coated with an ethynol-base paint without a top coatof KhV-53 paint even after curing it for 5-6 days (speci-mens No. 7, 12, 16).

It could be assumed that the difference in the be-havior of the coatings is due to the use of different typeof binders and the nature of changes occurring in thecoatings during film formation.

Table 4 presents the optimum drying conditions whichwere selected on the basis of the entire test set. TheTable also provides drying conditions recommended by ShipPainting Regulations established by the Ministry of theMaritime Fleet (Departmental Specifications MVN-51.67).

The table indicates that protracted curing of the lastantifouling paint coat prior to launching could be elimi-nated at all temperatures cited.

By and large the new painting schedules for the

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TABLE 4

No. of Paint name Coating drying time, hours atlayer temperatures 0C

-i0 -5 0 1 i0 20

A. According to test results

1 EYZhS-40 8-15 8-15 4 4 22 EKZhS-40 8-15 8-15 4 4 23 EKZhS-40 8-15 8-15 4 4 24 EKZhS-40 24 15 15 4 25 KhV-53 4 4 4 4 46 KhV-53 24 24 24 4 4

Total 76-971 67-38 55 24 16

B. According to Shi Painting Regulations,MinTstry-o the Maritime Fleet

1 EKZhS-40 8-15 8-15 6-8 4-6 2-42 EKZhS-40 8-15 8-15 6-8 4-6 2-43 EKZhS-40 8-15 8-15 6-8 4-6 2-44 EKZhS-40 24-36 24-36 16-24 8-16 4-85 KhV-53 4-10 4-10 4 4 46 KhV-53 4-10 4-10 4 4 4Curing 120 120 72 72 24

Total 176-221 175-221 114-128 100-114 42-52

KhV-53 paint would reduce ship dock time from 7-9 to 3-4days at -10, -5*C; from 4-5 to 2 days at 00 C; from 4-2days to 1.0-0.5 days at above-zero temperatures.

The new cure schedules for the KhV-53 paint arepresently being checked under operating conditions onships of the Baltic and Latiran shipping lines followingwhich they will be included in the Ship Painting Regulations(of the Ministry of the Maritime Fleet).

11

REFERENCES

1. Catalogs of "Chugoku Toryo Co. Ltd."; "Jotun SuretySystem for Ships"; "Marine Painting Specificationsand Product Data by International"; "Hempels MarinePaints".

2. Report on the Visit of a Soviet Specialist Delegationto Japan for Studying the Production Technology andApplication uf Paints for Hull Protection AgainstCorrosion and Fouling. Leningrad. TsNIIMF (CentralScientific Research Institute of the Maritime Fleet),1970.

3. Zubov, PI. and Golikov, V.S. Issledovaniyedolgovechnosti polimernykh pokrytiy v zavisimosti otusloviya formirovaniya i stareniya. (Study of theDurability of Polymer Coatings as a Function of Film-Foiining Conditions and Curing). DOKLADY AN SSSR(Transactions of the Academy of Science USSR), V. 161,No. 4, 1965.

4. Zubov, P.I., Sukhareva, L.A. and Golikova, U.S.Issledovaniye dolgovechuosti alkidnyich pokrytiy(Study of the Durability of Alkyd Coatings).Mekhanika Polimerov, No. 3, 1965.

5. Sukhareva, L.A. Golikova, V.S. and Zubov, P.I.Vliyaniye vodnoy sredy na vnutrenniye napryazheniyav alkidnykie pokrytiyakh (Effect of a Water Environ-ment on Internal Stresses in Alkyd Coatings).Lakokrasochnyye Materialy i ikh Primeneniye, No. 1,1965.

6. Kozlov, P.V. and Braginskiy, G.I. Khimiya i tekhnolog-iya polimernykh plenok (Chemistry and Technology ofPolymer Coatings). Moscow, Khimiya, 1965.

7. Peyn, G.F. Tekhnologiya organichesnikh pokrytiy(Technology of Organic Coatings), v.l. Leningrad.Goskhimizdat Publishing House, 1959.

8. Drinberg, A.Ya., Gurevich, Ye S. and Tikhomirov, A.V.Tekhnologiya nemetallicheskikh pokrytiy (Technologyof Nonmetallic Coatings), Leningrad GoskhimizdatPublishing House, 1957.

9. Ragg, M. Zashchita sudov ot obrastaniya i korrozii(Protection of Ships Against Corrosion and Fouling).

12

Leningrad, Sndpromgiz Publishing House, 1960.

10. Morskoye obrastaniye i bor'ba s nim (Marine Foulingand its Control). Moscow, Koyenizdat PublishingHouse, 1957.

11. El'terman, V.M. Ventilatsiya pri proizvodstvemalyarnykh rabot. Ventilation for Painting Operations.Industrial Ventilation. LDNTP (Leningrad House ofScientific and Technical Propaganda), 1967.

12. Dolgopol'skiy, I.M. Adl. Lak etinol' (Ethynoi Lacquer),Moscow. Goskhimizdat Publishing House, 1963.

13

PROCEDURE OF DETERMINING THE ADHESION OFTHERMOPLASTIC COATINGS

[By C.I. Shcherbinina and Yv.M. Kaplin. In "Tckhnicaeskayaeksluatatsiya morskogo flota. TeplokhimicheskiisIedo--

vaniya. Bor'ba s korroziyey i obrastaniyem" (TechnicalOperations of the Maritime Fleet. Thermochemical Studies.Control of Corrosion and Fouling). Transactions of theCentral Scientific Research Institute of the Maritime Fleet.No. 160, 1972, "Transport" Publishing House, Leningrad; pp. 26-30,Russian]

In the development and use of paint-and-varnish coatingsfor protecting underwater ship areas against corrosion andfouling, one of the principal requirements imposed upon themis their high adhesion to both the metal and the primarylayer. Good adhesion contributes to a longer service lifeof the paint-and-varnish coating and a reliable protection.

Studies [1, 2, 3] describe various procedures for bothquantitative determinations of coating adhesion to metalsof which most extensively used is the method of adhesionbased on critical values (4]. The essence of this methodlies in the fact that internal stresses increase linearlywith the thickness of the coating being formed to a certaincritical value at which spontaneous separation of the filmfrom the substrate occurs. The phenomenon is related tostresses occurring during film foimation at the film-substrate boundary; these stresses act against the forcesof adhesion much like mechanical tensile stresses and, uponreaching the critical value, break the film-substrate bond.Thus, adhesion may be rated on the basis of critical stressesin the film.

The cantilever method was selected for determiningstresses in thermoplastic coating [5] in which stresses,occurring in the film of an adequately strong bond, bend thesubstrate and force it free from its initial position. Thestress value is determined from the following formula

kg/cm 2

where h is the value of cantilever deflection, c; E is themodulus of elasticity; t is the thickness of the substrate,cm; 1 is the lengch of the film, cm; at is the thickness ofthe coating, cm.

14

The stress tests substrates were made of heat-treatedsteel tape (GOST 2614-65) measuring 0.5 x 15 x 120 mm.The substrate's working area was 90 mm long.

Rosin- and paraffin-base compositiors (GOST 797-41and GOST 784-53, respectively) were used for preparing thecoating material.

Prior to applying the coating, the substrates werecleaned with fine abrisives, degreased with an alcohol-ether mixture, and dr.ed. The specimens were placed on astrictly horizontal sui"ace and painted. The thermo-plastic coating was applied from a melt heated to I10-120 0 C.

Figure 1 shows curves reflecting stresses of thethermoplastic coatings as a function of their thicknessand rosin contents in them. The internal stresses were

,\\,

Figure 1. Changes in internal stresses as a function offilm thickness:

1 -- rosin, 30%, paraffin, 20%; 2 -- rosin, 50%;paraffin, 50%; 3 -- rosin, 70%; paraffin 30%.

found to decrease with increasing film thickness and rosincontent. The relationship between the film thickness andthe stresses permits stress extrapolation at the film-substrate interface. Thus, for 30% of rosin in theparaffin and a film thickness of 25#, the stress is about

40 kgf/cm2 and when the rosin content is increased to 50%,the stress for the same film thickness drops down to

20 kgf/cm2 . It may be well to point out that the internalstress for a film thickness above 4000is negligible.

The drop of stresses in the paraffin-rosin systemwith increasing the percentage of rosin may be attributed

15

I l I P ! i lI I1 J I I I !,i

to an increase in the content of functional COOH groupsconstituting the resionous acids of the rosin which con-tribute to strengthening the bond between the coating andthe substrate. The adhesion of a film with a high rosincontent to metal exceeds the internal stresses; as aresult, the film stretches and cracks due to the compo--sition's low cohesive strength.

A similar phenomenon was observed in films that wereformed from a rosin solution in alcohol-ether mixture.Figure 2 shows the kinetics of changes in the internalstresses of a rosin film applied to a steel substrate.

kg/cm A-

adn

Figure 2. Kinetics of changes in internal stresses in arosin film.

The process begins with the evaporation of the solvent andan increase in internal stresses with their subsequentdecrease. Total solvent removal causes a drastic drop ofstresses. The latter is caused (as indicated earlier) bythe cracking of the coating. Hence, the internal stressesin a 100# thick film consisting of 70% rosin and 30%paraffin reach their critical value at this point.

The data obtained here on thermoplastic coatingsadhesion to metal correlate well with those obtained bythe uniform break-away method. The principle of thismethod lies in the fact that the magnitude of adhesion israted by the force required to separate the adhesive fromthe substrate. In this case the force is applied perpen-dicularly to the coating surface. A 4s-steel die (35 mmin dia.) with a flat working end was used to determinethe adhesion of thermoplastic coatings. Dies withgrooved end surfaces were used as needed.

For applying the thermoplastic coating, the diewas heated in a thermostatically controlled chamber to100 C below the minimum coating application temperature and

16

then pressed into the coating. The die depression depthwas controlled by three stops (depending on purpose) seton the threaded surface of the die. The stop positionswere determined by a micrometric depth gage.

I'l.w break-away of the test coatings was characterizedby onu of three modes of failure:

-- adhesive, where the coating peeled offcompletely from the surface;

-- cohesive, in which the coating in itself wasbroken;

-- combined, where both the adhesive and cohesivefailures occurred.

Prior to use, the die was thoroughly cleaned, de-greased and dried. The coatings were applied at II0-1200 Cand cooled at room temperatures. The tests were conductedon a tensile-testing machine.

Figure 3 shows a directly proportional curve film-substrate bond strength versus rosin content in the coating.As the percentage of the rosin in the paraffin-rosin systemis increased, the value of adhesion rises. The resinousacid molecules in the rosin form a strong bond through thepolar COOH groups, so that the greater the number of polargroups in the boundary layer, the stronger the bond.

kg/cm 2

rosin content

Figure 3. Film-substrate bond strength as a function ofrosin contents.

As the film thickness is increased (Figure 4), theinternal stresses, which had occurred in the adhesiveduring film formation, reduce the forces of interactionbetween the film and the substrate and weaken the adhesivestrength.

17

kg/cm2

Figure 4. Film-substrate bond strength as a function ofthickness of a film containing 80% rosin and 20% paraffin.

The testing of the adhesive strength of rosin-and-paraffin-base thermoplastic materials destroys the bulkphase which is the weakest link in compositions of thistype. Unlike the boundary layer where the moleculararrangement is strictly oriented [6], it is chaotic in thebulk phase which reduces the forces of interaction betweenthe molecules and the composition's cohesive strengthrelated to them.

During the formation of the bond between the filmand the substrate in rosin-paraffin-base compositions, thedeformation in the bulk phase develops to a value corre-sponding to that of teh mechanical strength of the compo-sition. The low mechanical strength of the latter and theadhesion to the metal exceeding this strength cause theinternal stresses to drop due to the cracking of the coat-ing.

The inadequate mechanical strength of rosin-base filmsis due to the inhomogeneity of the rosin.

Conclusion

1. A feasibility study has been made to determine theadhesive strength of thermoplastic coatings by themethod of critical values and the uniform break-awaytechnique.

2. The adhesive strength of thermoplastic coatings is afunction of rosin content and film thickness.

3. With an increase in rosin content, the internalstresses drop while the film-substrate bond strengthincreases.

18

I.: psi .1

i**Iz

Qb/.

.- I .

OPERATING TESTS OF THE CATHODIC PROTECTION SYSTEM"LUGA" ON THE MOTOR SHIP KAPITAN PLAUSHEVSKIY

[Kysotskiy, A.A.; Central Scientific Research Institute ofthe Maritime Fleet, TRANSACTIONS, Technical Operations of

the Maritime Fleet. Thermochemical Studies. Corrosionand Fouling Control, No. 10; Leningrad "Transport" Pub-lishing House, 1972, pp. 30-38, Russian)

Hull corrosion of seagoing vessels is related not onlyto metal properties but also to the sea water salinity andtemperature (salinity determining the electric conductivityof sea water and, hence, metal corrosion rates).

On ships sailing in low-salinity basins the corrosionprocesses are inhibited and are concentrated at the bound-aries of the cathodic and anodic areas causing pitting --the most dangerous type of corrosion. Sea water tempera-ture not only governs changes in the electrochemicalpotentials of metals and the electrical resistance of thewater but also promotes corrosion processes. In the testsconducted under actual operating conditions involving con--trolled current densities and hull potentials -- ascathodic protection efficiency indices, primary consider-ation was given to the effects of sea water temperatureand salinity on electrochemical protection parameters(particularly on potential distribution over the hull andprotective current density). The operating tests wereconducted on the motor ship KAPITAN PLAUSHEVSKIY whoseunderwater hull area was painted four months earlier on thebasis of a standard chart.

The measurements of the potential distribution overthe hull were done at anchor in ports and in roadsteds aswell as during special stops (in the Arabian Sea on11 January 1971 prior to reaching the port of Bombay; alsoon 21 March 1971 in the Mozambique Strait on the cruisefrom Colombo to Odessa).

The measurements were done in the area of frames 0,10, 23, 45, 54, 70, 84, 100, 112, 130, 143, 155, and 170.The portable reference electrode was used 7-9m below thewaterline depending on the draft; the potentials weremeasured every other meter. Noteworthy is the fact thatthe potential distribution over the hull was fairlyuniform except for one case when the ship was in freshwater; in this case the potential variations in the anodeareas were rather distinct from one frame to the other.The cylindrical area of the outer hull plating exhibited

20

potential variations of 50-100mv; in the anode area of thebilge the potential was 2 to 2.5 times that of the protec-tive level (Figure 1).

Numerous measurements taken during the cruise both atanchor and underway showed potential drop rates to itsinitial value (650-750mv) and its rises to the protectivelevel (850mv). The findings cited in Figu. : were ob-tained in the Atlantic Ocean during the cruise from LasPalmas to Cape Town at average speeds of 14.5 knots.

Curve 1 shows the protective effect of salt depositsin the pores of the paint coats after current cutoff.These deposits close up the pores and restrict oxidizersupply to the metal's surface thus inhibiting hull potentialdisplacement toward the positive. Curve 2 indicates apotential rise to 850mv for a steady-state current density

of 0.0041 a/m2 (prior to disconnection) which takes 7 hours.

With a current density of 0.032 a/m2 (Curve 3) the pro-tective potential level is achieved within 20 minutes. Thecurves that were plotted on the basis of data obtained onthe ship at anchor are similar to those in Figure 2.

The tests included also numerous checks of protectionreliability and effectiveness involving 2, 4, 6, 8, and 10operating anodes. In all tests, both at anchor and under-way, the potential was maintained at the protective leveland was uniform all over the hull. However, with thecurrent intensity remaining constant the supply voltage(of the automatic static converter [ASCI) increases from4v for 12 operating anodes to 8v for 2 operating anodes.

To obtain certain current densities for various givenpotentials, several measurements were made of currentdensities measured to maintain potentials at 850, 800, and750mv both at anchor and underway.

The data given in Table 1 show an increase of 50% inthe required protective current density with a potentialdisplacement from 750 to 850mv during sailing and a 100%increase when measured at anchor. The voltage increasesby 20 and 40% respectively.

Figuze 3 reflects the data on the effect of sea watertemperatures on the required protective current densitylevel. The tests were run during the Atlantic cruise fromthe Canary Islznds to Cape Town.

21

Figure 1. Potential distribution on the underwater hullarea over the portable reference electrode prior to theship going into fresh water (1, 2, 3) and after the shiphad been in fresh water (4, 5, 6): 1, 4 -- over the sideplating from the waterline to the bilge; 2, 5 -- over thebilge in the anode area; 3, 6 -- over the bottom in thekeel area.

J

Figure 2. Curve reflecting the protective potential droprate (after disconnecting the protection system) and itsrise to the required value of 850mv.

22

TABLE 1

Hull ASC ASC ?rotec- Sea Sea ShiDPoten- Output Output ive Water Water Speedtial, mv Voltage, Current, urrent Temper- Sali!- knots

v , a )ensity ature ity

/m2 0C 0/00

850 2.5 22 .0050 28 35 15.75

800 2.2 18 .0040 28 35 15.70

750 2.0 15 .0034 28 35 15.70

850 2.0 20 ).0060 24 31 At anchor

800 1.8 12 ).0035 24 31 At anchor

750 1.2 10 ).0030 24 31 At anchor

Figure 3. Effect of sea water temperature on the pro-tective current density at 35 0/00 salinity and averagespeeds of 15 knots.

23

The data in this figure show that for a constant seawater salinity there is a nearly linear relationshiphbtween the temperature on the one hand and the protectivecurrent density on the other, at least within 17 to 30 *C.

The effect of sea water salinity on electrochemicalprot, ction parameters was studied during the cruise fromthe Bengal Bay to Calcutta over Hooghley River and tc theport Chalna over Pusur River. Because of the tidal flow,the salin 4 ty -f the river water increased from 3 to 33 0/00with approaching the bay.

The findings of these studies given in Figure 4 showan abrupt drop of supply voltage when going from freshwater to salt water (Curve 1) and a much slower rise whengoing from salt water to fresh water (Curve 2), most likelydue to films of cathodic deposits formed on the underwaterhull area. The protective current density is almost doubledwhen going from fresh water to salt water and decreases byabout the same factor when going from salt water to freshwater.

/I. V/!

:,2

12;

I' -

Figure 4. Effect of sea water salinity on the parametersof electrochemical protection with the ship going from freshwater into salt water and conversely.

24

Curve 5 shows the effect of sea water salinity onprotective current density after the ship has been in freshwater for a long time and the subsequent formation of acathodic film (segment ab, Curve 5) with the ship sailingin sea water at all times.

When the ship stays in fresh water, the cathodicdeposits in the paint pores are washed out, the metal isrevealed, and the corrosion process becomes activated.The current densities required to suppress these processeswith the ship going into a more aggressive environment aremany times greater than those required by the ship beforegoing into fresh water. The subsequent decrease of pro-tective density for sailing in sea water (segment ab,Curve 5) indicates restoration of the cathodic film.

The tests included current intensity measurementsbetween the propeller and the hull using the zero resistancemethod which eliminated voltage drops due to resistances inmoving contacts and in equipment. The measurements includedalso propeller potentials under various conditions of ef-fective protection at various sktip speeds. The currentbetween the propeller and the hull can be measured onlyduring shaft rotation when there is an oil wedge (withsome resistance) between the bearing and the shaft.

The data on propeller potentials and current flowingbetween the propeller and the hull under various conditionsof electrochemical protection and ship speeds are cited inTable 2. Analysis of these data that the current recordedbetween the propeller and the hull is the higher the greaterthe potential difference between the propeller and the hull.The magnitude of this current fluctuated (during the testperiod) within 1-2a. The potential differenre between thepropeller and the hull varied from 50 to 200mv in all thesetests.

The operating tests conducted on the motor ship KAPITANPLAUSHEVSKIY have demonstrated that cathodic protectiontogether with painting provide reliable protection of theunderwater hull area against corrosion damage. The pro-tective current density for an 850mv hull potential was

20.004-0.007 a/m2 . In some instances after the ship hadbeen sailing in fresh water, the protective current density

2increased to 0.02-0.03 a/m

25

.":' TABLE 2

'Ni ,1 9 2.7 1 1 (1 (1I*1 I 1 70 c 01 '.

0,!':JiI In V.Il"

*-* ~ " A..:,": :: ''.' P 1V.. K'A !0000 j 7Z.) 1 110 1.5 0 , I.7

5.9 1 1! A: -1m: (?..I152 2(,, 0 10 tO0 7i I 10 . 1.3 0. 1 W

20 1 f I. 1! A.t -- v i-I. .

21 21,1. 11 lw1- h1 .fi# 1i .I; IZ jI Z- ( Y;)71 7015 0

-;"y 1 Av uirw la iosl I 1 -0 119 M.-25A #,,f i I ;':sif ON I 1,.7 -1.4) 0.1J6 . 1OIO .. ( .

-- a 1.1

26 .4r1 !tI! al!t 15 0 ? 31.0 I r'o4 0,005S E40 20 0.5r 0.0VIM

27 tI excal :V%75 29 35.0 RD0 0.000 700 NCO 2.0 0.16028 ApP:,Aa mope Cc-;j~, 2& 35.0 1 Ul 0.30 84 - -

29 y); " 14.C W. 35.r). 0o 0.0210 O 2 0.30 31.-,. 17.35 2t, 35.0 t'i 0.01-o70 o ?C 00 2,2 0,17231 )ill 1:l:~ ~~' 15.*., 27 35.0 K'O( 0.0131) Of0 2,3 2,7 0,210

33 ipi *CTo*u.a 23 31.0 J w) 010060 850 - - -

34 13'!.j14.5-, 24.5 W2.0 f s 0.0160 870 110 0.9 0,0703. i:i P. l.Av a 1!.7 2.1 2oo 50 0.0s POO - -

36 11%,11 p. 11i jv1: 1.7 23 7. Z # 5 7 0 1 z 0.6 016ZO37 :8;II,. Wna3111 .Z 5 J.5 !0 0,Ol3 (630 2210 1's 0,1401

38 :i 15.0 28 3,. FL~,IO 0090 O 170 1,15 0.117

Best AvaiabeCp26

'TABLE 23C 15,'111 lh:I ;;:WiL ct'utl 1,O 29 ' 31,0 860 0,008i G';0 "20--) "0,~ 0 ,C..'i

4,0 ,13,t 29 ;3,1, 8(,0 0,0073 -- -

41 -7(111 I, ;..,.'w 1,, II 2I 20 3-1, b0 0,0065 730 130 1,5

42 2q; I I :I:.m:,iec.. i 13,1 20 35,0 850 0,O073 .00 ,23 ,,

y O\. l 1 ;M~ (PaII1 L5 I), . 7 I) '' I""(I.mo:: Kc,ro) "3,0 F~ro 0 00 3 6611) 2,3

9,'IV Vr. IIr:y. (p -hoit 15,4 17 37,0) 850 0,00W5 C F 200

455,.5 1G 3!.), 11Z 0 0.03

46 0or": 17,2 15 3 7, 5 7

47 12 " 1 \ ll; po.ir 17,4 15 3.,, "17 0 .;017 V -- --48 IIV %c' ,.':o pe 13,0 10 16,0 K0 C. 003

4949C 6 no 13 i:-p',.:i 1071 r..t'-v , ' C, > : t ;i.'t, ' , n?, i !., z . C 10 :0 27 ,c2 .1,'-'-: ''.L tLlnl'c, ,'.c¢:,. c ,,

Legend for Table 2:

1) Date2) Navigational region;3) Ship speed, knots;4). Sea water temperature, OC;5) Sea water salinity, 0/00;6) Hull potential, mv; 27) Protective current density, a/m;8) Propeller potential, my;9) Propeller-hull potential difference, my;10) Current between propeller and hull, a;11) Arbitrary density of protective current rn propeller,

a/m2 ;12) Black Sea13) Bosporus14) Marmara Sea15) Dardanelles16) Aegean Sea17) Mediterranean Sea

27

Legend for Table 2:

18) Atlantic Ocean IMorocco)19) Atlantic (Canary Islands)20) Atlantic (West Sahara region)21) Guinea Bay (Equator)22) Guinea Bay (Congo region)23) Atlantic (Angola region)24) Atlantic (Cape Town region)25) Indian Ocean26) Indian Ocean (Madagascar region)27) Indian Ocean (Equator)28) Arabian Sea28a) P-mbay anchorage29) Arabian Sea30) Arabian Sea31) Indian Ocean (Ceylon region)32) Bengal Bay33) Bengal Bay33a) Bengal Bay anchorage34) Bengal Bay35) Pusur River36) Pusur River37) Bengal Bay38) Bengal Bay39) Indian Ocean (Ceylon region)40) Mozambique Strait41) Indian Ocean (R.S.A. region)42) Atlantic Ocean (R.S.A. region)43) Guinea Bay (Congo region)44) Atlantic (Morocco region)45) Gibraltar46) Mediterranean Sea (Algiers region)47) Tunisian Strait48) Blacl: Sea49) From 6 to 13 February 1971 -- protection disconnected.

Calcutta anchorage -- fresh water.From 16 to 27 February 1971, Chalna anchorage, freshwater.

28

EFFECTIVENESS OF ELECTROCHEMICAL PROTECTION OF 25L STEELAGAINST CORROSION CAVITATION IN FLOWING SEA WATER

(By G. K. Gavrskiy, N. I. Yermolenko, Yu. Ye. Zobachev(Candidate of Technical Science), A. V. Kurdin (Candidateof Technical Science), Yu. V. Luk'yanova, and R. N.Metcl'skaya. TRANSACTIONS of the Central Scientific Re-search Institute of the Maritime Fleet. Technical Opera -rions of the Maritime Fleet. Thermochemical Studies.Corrosion and Fouling Control. Transport Publishing House,Leningrad, 1972, No. 160, pp. 38-46; Russian]

Earlier works (1-4] dealt with the feasibility of usingelectric current applications for protecting metal structuresagainst the effects of corrosion cavitation both in riverand sea waters. These studies concerned the effectivenessof electrochemical protection of metals in the case ofhighly developed cavitation, i.e. when the mechanicaleffects predominate over the chemical effects (corrosion).

For practical purposes and the solution of relevantproblems, it is of interest to determine the feasibilityof applied current protection against moderate cavitation,i.e. when the mechanical effects and the chemical effectsare commensurate.

Within the last three years the Far Eastern Branch ofthe Central Scientific Research Institute of the MaritimeFleet has been conducting investigations on the effective-ness of electrochemical protection of 25L carbon steelagainst corrosion cavitation damage in sea water at flowvelocities of 24 to 32 m/sec corresponding to the linearvelocity of a propeller blade edge in modern vessels.

The tests have been conducted with the aid ofspecially designed units: a diffuser and a jet blower.Both units were used for testing the specimens in sea waterat flow velocities of 24 to 32 m/sec. The flow of waterin the diffuser was produced by an ordinary pump, whilethat in the jet blower -- by a centrifugal force producedby rotating a spindle with the test specimens on it. Thecavitation effect in the diffuser was produced by specialbarriers in the flow channel; in the jet blower, cavitationbubbles were produced by placing the specimens at aspecific angle to the water current. Both these unitsdescribed in [4] were supplemented in this experiment withan electrochemical measuring device (figure 1). Thespecimens were polarized by a steel electrode. A P-307potentiometer was used for voltage measurements. A

29

L .. . ... .r .. . ... . . . ....

I.'.o -ot(, otifoheter

ii

Figure 1. Diffuser-type testing unit with an electro-chemical measuring circuit.

calomel-loaded reference electrode was used in all cases.

The testing lasted 100 hours.

Table 1 shows the test results.

It was demonstrated within these 100 hrs of testingof 2.5L steel at flow velocities of 32 m/sec that pro-tective current decreases with time.

2The protective current produced by 10-a/m polari-

zation for Curve 1 is 2540OMa (curve intersection pointwith straight line A - A corresponding to a 0.660-vpotential); after 30 hours of polarization, the protectivecurrent decreases to 582,#a. Subsequently, the protectivecurrent decreases at a slower rate. Thus, after 50 hoursof polarization, the protective current is 550pua, after75 hours -- 496/aa, and after 100 hours, the prntectivecurrent is 441gMa.

Polarization with current of 2.5 a/m2 (Figure 2,b) atflow velocities of 32 m/sec causes a slightly lesser changein protective current with time. Thus, 30 hours of polari-

zation with 10-a/m2 current decreases the protective current

by a factor of 4.36, while polarization with 2.5-a/m2

current within the same numer of hours decreases the pro-tective current by a factor of 4.3 (from 2540 to 590.0a.)

30

TABLE 1

24

is 1 ,41

I ,. ) , .•

, ti !

I j ; . ! I ' -

j 1i I i.'.'

:.f ,: !. I l,.+ " ,

I I

)I '

":7 I ~ I 'h . I . ;L ,',

I.."

.. "...

a',

' , i ' a ,

":' '""

I t d i t '?.

',. I*.:

t.* , l .

* .

312

--

:.+It+:' j :~ I .+.,

... . .. .. .('+*:"

I + I, * . .

" , ), ! ., I :.,".

.

I

~

1 31

* . 1

Legend for Table 1:

1) current density, a/rn2; 4) degree of protection, 1;

2) flow velocity, rn/sec; 5) diffuser;

3) weight loss, g/ 2-hr; 6) jet blower.

1 I0

Fiur 2.Ctodc1,..:i ure f25 te potdduring poaiain.)40am cret ) .- 2cret

I32 .... .. Y

- . , . .Al

.. .. . Best

* I .'* ~ ]

Legend for Table:

1) No. of curve;2) Figure 2,a;3) Figure 2,b;4) polarization time, hrs;5) without polarization.

About the same relationships were obtained in testson specimens at other flow velocities. At 28 m/sec and a

10-a/rn current there is a decrease in protective currentas a function of specimen polarization time. Thus, if theprotective current was 1750 .a (at the beginning of theexperiment), it decreased after 5 hrs of polarization to1270 ja. After 30 hrs,-the protective current was as lowas 353,#a which is one fifth of its initial value. Forthe same flow velocity and a polarization current of

2.5 a/m2 , however, the protective current decreases at aslightly lower rate: at the beginning of the experimentit was 1780, Aa, after 5 hrs -- 840,#a, and after 30 hrs itwas 420 jia, i.e., 4.4 times less than its initial value.The results of these tests are given in Table 2.

The table shows that the protective current reduction

factor for polarization with 10-a/m2 current, with a de-crease in flow velocity, increases from 4.36 for 32 m/secto 6.15 for 24 m/sec. This may be attributed to the factthat a stronger cavitation decreases the effectiveness ofthe hydrogen cushion whose damping properties (for thiscurrent density) are those that produce the protectiveeffect. When polarization is effected with a

2.5-a/m2 current, hydrogen is liberated to a lesser degree;the film which is formed during polarization removes itself

33

Best Available Copy

TABLE 2

212

1) flo ve o i y • ' , I,

,&a

") I d .. ... .I I a

I 3. PrIt"c""v cie as a fi.'"

__ - , • - .j*'.I-J : I ...

21 I ' '. : ,, '_ I ...

I .. ' i,., I .- : I , .

Legend for Table 2:

1) flow velocity, m/sec;2) polarization current density, a/rn2;

3) protective current at the beginning of the test,Aa;

4) protective current after 30 hrs of polarizatlon,5) reduction factor of protective current.

t\ •

* Nd

"". - . .: . .* ' i

Figure 3. Protective current densities as a function of

polarization time with 10 a/rn (1) and 2.5 a/rn2 at a flowvelocity of 32 r/sec.

34 Best Avaijable Copy

at flow velocities of 28 and 32 m/sec; the protectivecurrent build-up factor, therefore, changes only slightlyfor all flow velocities (from 4.30 for 32 m/sec to 4.55for 24 m/sec.

The protective currents as a function of polarizationtime were calculated from the curves plotted during speci-

men polarization with 10- and 2.5-a/m 2 currents. The

results are given in Figure 3.

It was observed (at all experimental flow velocities)

that polarization with 2.5-a/m2 current F 1duced ahydroxide film on the specimens' surface (except forcavitation-affected areas) while there were no films on

specimens polarized with 10-a/m 2 current. This suggeststhat protection is governed by various mechanisms of

current effects: for a 10-a/m 2 current density, thepotential is 1 v at which point there begins abundantliberation of hydrogen on the specimen's surface hinderingfilm formation. The fairly high degree of protection isattributed to the beneficial effect of the hydrogencushion on the specimen's surface.

For 2.5-a/m 2 current densities the potential is 0.660v. It was observed that the films that were formed inflowing water were much weaker than those produced in calmwater (even with polarization currents being many timeslower than those for specimens in flowing water). Polari-

zation of specimens with 10-a/m 2 current for 25 hrs in calmwater and then 75 hrs in flow has shown that the cathodicfilms (though very weak) that have been formed duringpolarization in calm water are readily destroyed in flowingwater regardless of its velocity. In a similar experiment

involving 2.5-a/m2 current the percentage of film preser-vation after 25 hrs of testing in flow was much higher,it was also show,, that polarization in calm water with

0.4-a/m 2 current yields an equally strong film (Figure 4).The film forming time in the latter case was 25 hrs.Figure 4 shows that film formation is at its minimum when

produced under 0.4-a/m 2 current. This observation seems

35

Figure 4. Potential variation rate of the steel specimenafter disconnecting the polarization current (flow velocity,32 m/sec). Polarization done in calm water.

Figure 5. Potential variation rate of the steel specimenas a function of polarization current density.

to be of prime importance since it permits a more economicalrating of power in designing electrochemical protectionsystems.

For specimens that have not been treated for pre-polarization, the optimum conditions for film forming were

produced with current densities of 1.5-2.5 a/m2. Thisconclusion has been corroborated by studies on changes instationary potentials as a function of time after discon-necting the polarizing current (Figure 5). The filmforming time was 100 hrs. Figure 5 shows that the minimumof affalls on deposits formed at current densities of

21.5-2.5 a/m. The comparison of curves in Figure 4 andFigure 5 shows that variations of flow velocities produceconsiderable changes in film forming. Thus, if the optimum

current density for calm water is 0.4 a/m2 , a flow velocity

36

of 32 m/sec would require 1.5 a/m2 . The potential incre-ment (for a flowing electrolyte) is attributed basicallyto the mechanical effect of sea water flow hindering theformation of protective films. The marked reduction inthe protective current is attributed to the growth of thecathodic film which leads to screening the specimen'ssurface. This increases the true current while decreasingthe total protective current. Termination of film growth(after 25-30 hrs of polarization) suspends the drop ofprotective current.

Conclusions

1. Electrochemical protection is an effective means ofincreasing the resistance of carbon steel to corrosioncavitation in sea water.

2. For sea water flow velocities ranging from 24 to 32m/sec and corresponding to the linear velocities ofpropeller blade edges in modern ships, considerablechanges in the degree of protection occur only forpolarization current densities ranging from 0.5

a/m2 to 10 a/m2 (42 and 77%, respectively).

3. The protective current markedly decreases as a functionof time at all flow velocities.

4. Prepolarization of specimens in calm water reducesconsiderably the protective current during subsequenttesting in flo.wing water.

REFERENCES

1. Glikman, L.A. and Zobachev, Yv. Ye. Vliyaniye katodnoypolyarizatsii na kavitatsionnuyu stoykost' uglerodistoystali (Effect of Cathodic Polarization on the Resistanceof Carbon Steel to Cavitation). "Metallovedeniye itermicheskaya obrabotka metallov" No 4, 1956

2. Len'kova, L.N., Vysotskiy, A.A. and Zobachev, Yv. Ye.Elektrokhimicheskaya zashchita metallov ot kavitatsion-nogo vozdeystviya vysokoy intensivnosti (Electro-chemical Protection of Metals Against Highly IntensiveCavitation). Inf. sb. TsNIIMFa, No. 49 (149).Moscow. Central Office of Scientific and TechnicalInformation of the USSR Ministry of the Maritime Fleet,1967.

37

3. Kurdin, A.V., Luk'yanova, yv. V., Vysotskiy, A.A. andZobachev, Yv. Ye. Elektrokhimicheskaya zashchita otkavitatsionnogo ra zrusheniya razlichnoy intensivnosti(Electrochemical Protection Against Cavitation Damnageof Varying Intensity). TR. TsNIIMFa, No. 116, Lenin-grad, "Transport" Publishing House, 1969.

4. Kurdin, A.V. Issledovaniye povedeniya materialovgrebnykh vintov i nekotorykh sposobov zashchity ikhv usloviyakh korrozionno-mekhanicheskogo vozdcystviyamorskoy vody (Behavior of Propeller Materials andCertain Methods of Protection on Exposure to Corrosiveand Mechanical Effects of Sea Water). Author'sAbstract of Dissertation for the Candidate degree ofTechnical Sciences, Vladivostok, 1970.

3. Kurdin, A.V., Luk'yanova, Yv. V., Vysotskiy, A.A. andZobachev, Yv. Ye. Elektrokhimicheskaya zashchita otkavitatsionnogo razrusheniya razlichnoy intensivnosti(Electrochemical Protection Against Cavitation Damageof Varying Intensity). TR. TsNIIMFa, No. 116, Lenin-grad, "Transport" Publishing House, 1969.

4. Kurdin, A.V. Issledovaniye povedeniya materialovgrebnykh vintov i nekotorykh sposobov zashchity ikhv usloviyakh korrozionno-mekhanicheskogo vozdeystviyamorskoy vody (Behavior of Propeller Materials andCertain Methods of Protection on Exposure to Corrosiveand Mechanical Effects of Sea Water). Author'sAbstract of Dissertation for the Candidate degree ofTechnical Sciences, Vladivostok, 1970.

38

DISTRIBUTION OF HIGH-FREQUENCY VIBRATION IN HULLS OFKRASNOGRAD-CLASS SHIPS EQUIPPED WITH ULTRASONIC

ANTIFOULING PROTECTION SYSTEMS

[By P.S. Sheherbakov, F. Ye. Grigor'yan, and N.V. Pogrebnyak.TRANFACTIONS of the Central Scientific Research Institute ofthe Maritime Fleet, TECHNICAL OPERATION OF THE MARITIMEFLEET. THERMOCHEMICAL STUDIES. CONTROL OF CORROSION ANDFOULING. Transport Publishing House, Leningrad, 1972, No.160, pp. 68-72; Russian]

Ultrasonic protection has been used in the last fewyears to reduce fouling of underwater hull parts. Themaritime fleet has now about 20 vessels equipped with ultra-sonic antifouling protection systems. Despite the fact thatthe latter have been in use for over 10 years, there arestill no data on the distribution of high-frequencyvibrations over hull structures.

The objective of this study was to check the efficiencyof ultrasonic antifouling protection and study of vibrationdamping in the hull by measuring high-frequency vibrationson a KRASNOGRAD-CLASS ship.

The ultrasonic system on these ships incorporates avacuum tube ultrasonic oscillator with a 200-w power outputand four more oscillators. The oscillator's output voltagefrequency varies within 17-30 KHZ. The oscillator uses aself-excitation, and frequency-modulation circuit.

The magnetostriction oscillator consists of four nickelplates assembled in a package and soldered to a steel prismwhich is welded to the inner side of the hull plating. Theplates carry a winding in which a variable magnetic field isproduced. Under the effect of the magnetic field, the platepackage, possessing a magnetostriction property, undergoesperiodic. changes in size. The vibrations of the package aretransmitted through the prism (waveguide) to the outer hullplating.

Measurements of the oscillation acceleration amplitudelevels were conducted on KRASNOGRAD-CLASS motor ships usingDanish measuring equipment of the firm Bnuel and Kjaerw.The 4331-model Danish pickup with a linear accelerationfrequency characteristic up to 60 KHZ was used as the ultra-sonic vibration detector. A microphonic amplifier with anoctave filter and a linear frequency characteristic up to40 KHZ was used as the measuring device.

39

The figure below shows measurements of vibrationsproduced by an ultrasonic protection exciter in the secondbottom area on KRASNOGRAD motor ships both during dockupand while afloat. It is shown that the vibration levelalong the ship hull decreases with an increasesin distancefrom the vibration source (exciter). In the immediate vi-cinity of the radiator installation site (3-5m from thesource) the damping decreases by 20% due to energy losses inhull structures and sound radiation to the water. Whenwaves propagate through bulkheads, abrupt damping is observed.

The data obtained are in some variance with those instudy [1].

A dock inspection of KRASNOVRAL'SK and KLIN motor shipsin June 1970 corroborated the authors' assumption on vibrationinsulation in the bulkheads. Along the hull sides therewere fine balanus strips at the weld areas of the bulkheadsand framing to the hull (at minimum vibration areas) forminga typical "zebra pattern".

At a considerable distance from the exciters -- an areawhere the oscillation acceleration level was below 70 db --there was a dense balanus population. This shows that itwould be impossible to ensure a fairly uniform vibration levelalong the entire hull and a good protection against foulingeven if this method has its advocates [2, 3].

A comparative analysis of the operation of ultrasonicprotection on KRASNOGRAD-CLASS ships and those on project394 (under the Central Scientific Research Institute of Trans-portation Construction) has shown the same pattern of ultra-sonic vibrations to be true for ships of different dis-placements.

In order to determine the operating effectiveness ofultrasonic systems, the Central Scientific Research Insti-tute of the Maritime Fleet conducted vibration studies inthe oscillator areas on all ships equipped with suchsystems.

The findings are presented in Tables 1 and 2.

As shown by the measurements the difference in thenumerical values of vibration ranges within 25 decibels;all ships used the same type of equipment. The differenceis attributed to misalignment of the TTAGD oscillator tubesystems of the power amplifier during operation.

46

.I: . /, : .-- '<" ',

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..- N . i // .- " .--.• .. :: )/ ... "• " ,

(u)

.

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I,

Distribution of ultrasonic vibrations along the lengthof the KRASNOGRAD motor ship measured in the secondbottom area:

-during docking; while afloat

Legend: (1) relative vibration level, db;(2) larboard side;(3) stern;(4) bow;(5) Transom No. 5;(6) observation site;(7) Framing;(8) starboard side;(9) Oscillators

The results obtained here show that the hull vibrationlevel of ships having ultrasonic protection in the acceler-ation frequency band of 16 KHZ remains within the 100-120db range.

41

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42

TABLE 2

Vibration level on MICHVRINSK-CLASSSHIPS in the oscillator area 16-KHZ

Name of Ship octave band, db

larboard larboard starboard starboardside (bow) side side (bow) side

(stern) (stern)

CHERNYAKHOVSK 107 113.5 123 91.5

L'GOV 94.5 85.5 104.5 112

IZHEVSK NONE 85.5 NONE 83

Conclusions

1. The structural rigidity of the hull affects vibrationdistribution along the hull. In placing the oscil-lators, one must take into consideration the vibrationinsulation and damping properties of the various hullareas.

2. Ultrasonic vibrations within 115-125 db reduce con-siderably the fouling of the underwater parts of thehull.

REFERENCES

1. Kornev, V.V. Fizicheskiye zadachi ul'trazvukovoyzashchity sudov ot obrastaniya (Physical Problems ofUltrasonic Antifouling Protection of Ships). Author'sAbstract of Dissertation for the Degree of Candidateof Technical Sciences. LKI (Leningrad ShipbuildingInstitute) 1965.

2. Aksel'band, A.M. Vliyaniye ul'trazvukovykh kolebaniyna processy obrastaniya korpusov sudov i na morskiyeobrastaniya (Effect of Ultrasonic Vibration on Foulingof Ship Hulls). Tekhnologiya sudostroyeniya, No. 5,1964.

43

3. Subkbew, H.J., Schultz, S. Schiffbantechnik, V.3,No. 7, 1963.

44

STUDY OF THE VOLTAIC COUPLE HULL-PROPELLER

[Yevdokimov, O.V. and Shcherbakov, P.S.; Central ScientificResearch Institute of the Maritime Fleet, Transactions,Technical Operations of the Maritime Fleet. ThermochemicalStudies. Corrosion and Fouling Control, No. 160, p. 72-78;"Transport" Publishing House, Leningrad, 1972; Russian]

The most intensive source of current on the underwaterhull portion is the voltaic couple hull-propeller.

Quantitatively, the galvanic current of this couple maybe determined by the formula

I. -.--....... n _ P ...."

where Rle is the propeller leakage resistance; Rin is the

internal resistance of the bearings; Rpa is the paint

resistance; Rh and Rpr are hull and propeller polarization

resistances, respectively; Uh-Upr is the potential

difference between the hull and the propeller.

The values of the terms in Formula (1) are determinedfrom the following expressions:

The propeller leakage resistance

- 1 I(A)le - -,, ' ; [ ' '(!

where is the electroconductivity of water, l/ohm'm;

r is the propeller radius, m;

K(k); K(k') are the complete elliptic integrals of the

first kind with moduli K = h0 - r0/h0 + r0 and

k' =V 1 K2 , respectively;

45

h is the distance from the center of the propeller to theship hull along the normal to the axis of the shafting,m.

The hull polarization resistance

Rh = Bpr/Spr (3)

where B is the specific polarizability of the propellerpr

(in ohm'm2 ) which is 0.3 for a ship in motion and is 7.7m2

at anchorage; S is the propeller surface, .pr

The internal resistance of the shaft line representsa system of parallel resistances of journal bearings.

The resistance of a single bearing is determined fromthe following formula

I - . ( . , )

where to is the electric conductivity of the oil; h is the

clearance between the shaft and the bush, m; rl, r2 are

the radii of the shaft and the bush, m;

h > (3 to 8) [Hsh + Hbn];

Hsh; Hbn are the mean square heights of the shaft surface

roughness and that of the bush, respectively.

The total resistance of the internal circuit

in

The effective current values may be determinedgraphically if we know the so-called internal curve of thevoltaic couple hull-propeller representing a slightlymodified polarization curve in which the abscissa axisreflects the current and the Y-axis--the potential differ-ence between the hull and the propeller. Then by measuringthe effective voltage between the shaft and the hullue and using the diagram in Figure 1, we can determine

46

the current value of the hull-propeller couple. Thetangent of the inclination angle of a straight line drawnthrough both the origin of the coordinates and theoperating point determines the resistance of the internal

'fupr Ic.pl

Figure 1. Characteristic of the voltaiccouple hull-propeller

section of the circuit (the stern and journal bearings.

The diagram may be plotted according to a method citedin study [1]. The table below gives hull-propeller couplecurrent values for various types of ships measured by anammeter circuit with zero resistance. The measurementsindicate that the current value depends on many factors,such as propeller material, water salinity and temperature,the number of protectors installed on the hull, and thestate of paint on the underwater portion of the hull.

If we recalculate the obtained data to current densityon the propeller after connecting it electrically with the 2hull, then the current density values will be 0.1-0.12 a/m

for carbon steel propellers; 0.2-0.25 a/m2 for stainless

2steel propellers; and, 0.5-1.5 a/m for propellers ofLMHzZh-55-3 brass.

The above short-circuit current measurements correspondto the maximum corrosion current produced between the hulland the propeller. Hence, in order to eliminate hullcorrosion and provide propeller protection, it is necessaryto ensure equality between the current of contact corrosionand that of protection.

It should be noted that the basic operating criterionfor a voltaic couple are the resistance relationships betweenthe electrodes. Specifically, application of external currentresults in potential redistribution over the electrode

47

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48

surfaces, addition of corrosion current and protectioncurrent vectors, and a voltage drop on the internalresistance.

During the cathodic polarization of the hull, aportion of the current is short-circuited to the propellerwhich leads to a reduction of the electrode potentialdifference between the propeller and the hull (an increasein polarization resistance Rp2) and, consequently, a de-

crease in the galvanic current of the hull-propellercouple. The amount of current flowing to the propeller isbasically determined by the internal resistance of thebearings Rin as well as by the location of the cathodic

protection anodes. Such a system represents a three-electrode voltaic system whose equivalent circuit is shownin Figure 2.

In this system

1) the journal and stern bearing resistances are re-placed by a single equivalent resistance Rin connected inseries with the source emf;

2) the leakage resistance Ra.h (anode-hull) partici-

pates fully in the cathodic polarization of the hull. Theamount of current flowing to the propeller Ia.pr can beignored.

Figure 2 may be used as a basis for determiningcurrents in various systems using the following formula

(Rh.~ ~ I -=Eoh'. rr >in I. h.pr 2 so

P- r1 .pr + (Rh.pr + Raopr+ Ra.h i 2 - R 0.

-1 ha.2 h i+ i.h . R 3 1c.p ) c.p

By solving this equation, one may determine thefollowing:

49

iC

I ' 1

[±i jJ.pi 4. h~

a.rc"

Figure 2. Equivalent circuitry of the hull-propellersystem of a ship with cathodic protection

E -- source emf, i.e. the potential difference of theso

voltaic couple hull-propeller (Uh-Upr); E -- cathodic

protection source emf, i.e. the potential differencebetween the emf of the cathodic protection source and theeffective emf of the couple AU produced by the voltaicinteraction of the anode with the hull; ECop = 0.95 Uv-AU

(5% voltage drop in the network; Rin -- internal circuitry

resistance (for the hull-propeller couple), resistance ofjournal and stern bearings - the electron conductivitysection; Rh.pr -- the leakage resistance between the

propeller and the hull; Ra.h -- the leakage resistance

between the anode and the hull; Ra.pr -- the leakage

resistance between the anode and the propeller; R --

the control resistance in the cathodic protection platecircuit; i1, i2, i3 -- are currents in the various systems.

50

The current between the hull and the propeller

E [R R +R (R +R )1-E R Rlh.pr=i 1-i2= so 'a.h a-pr c.P a~L1

ZLR

The current between the anode and the hull

E ER R +R. (R +R )]-E R Ri022 E°p[a.pr h.pr+ in a.pr h.pr so h.pr c.p (6)Ia.h=i - = . . ..ZR

The current between the anode and the propeller

Rh (E +E)+R hRiE +RhR E,

a.pr 2 -R

where R-- Ra.pr Ra.h Rh.pr Rh.pr Ra.h + .pr )Rp R in+

(Ra~ +R )Rh R + (R + R )R R.a. h a.prn.pr c.p h.pr a.pr a.h in'

Analysis of these formulas indicates that when theinternal circuit resistance increases and becomes muchgreater than the resistance of the electrolytic (outboard)section of the circuit (Rpr>Pa.h)l then the current flowing

through it exceeds that flowing through the internalsection of the circuit. The total resistance increasesand the current value Ia.pr can be ignored (Ia.pr = 0).

This is accompanied by polarization processes leadingto changes in the potential difference between the propellerand the hull -- a fact that had been repeatedly checked outunder operating conditions. Thus, for example, during thecathodic polarization of the motorboat PULKOVO hull, theinterelectrode potential difference between the propellerand the hull was 50-70 my; without cathodic protection thedifference was as high as 200 my.

In this case R in>>O; R a.pr)0; I a.pr= i 2 = 0; using

equations (5) and (6) we will obtain

Ia.h = Ih.pri3/i1 . (8)

51

If there is a drop in the internal resistance (due toshaft contact, water getting into the bearings, etc.), thenthe voltage between the shaft and the hull decreases, thecurrent value will exceed zero (Rin ' 0; Ra.pr 1 0;

I 0), and equations (5) and (6) would assume the

following form

ERsoR cRa.h -ER R h.PrI sh.pra a.h socp "

Then

Ia.h h.pr i 3 - i 2 / i 1- i 2 = I h.pr Rh.pr / R a . h " (9)

As seen from Formula (9), in the case of a highinternal resistance, the greater the difference betweenthe cathodic protection current Ia.h and the initial

current of the hull-propeller couple, the higher the currenti3>i which, in turn, is determined by the relationship

between these circuits. When i3=il, the current in Formula

(8) will be equal. Otherwise this equality is determinedby the condition Rh.pr>Ra.h . When Rh.pr=Ra.h' the currents

in Formula (9) will be equal. This may be achieved byincreasing the resistance Ra.h which, in turn, can be

effected by using a larger anodic shield.

The journal bearings between the hull and the propeller(see table) could pass currents up to 20a high which, inturn, may cause erosion of the bearing metal both on theshaft and the propeller. This phenomenon has been recentlycontrolled by contact brush devices to short-circuit theshafting to the hull. This would eliminate the effect ofthe hull-propeller source. The three-electrode systemdiscussed above is now becoming a two-electrode system.

Equations for currents flowing in the systems areexpressed as follows

52

i2(Ra.h +Ra.pr Rh.pr ) - i 3 Ra.h = 0;

iR h+i 3(Rah+Rh) E

By solving these equations we will obtain

the current between the anode and the hull

EPP (Rapr+Rh ".pr) (10)

a.h 3 2 IR

the current between the anode and the propeller

E R

a.pr 2 = R

where

ER= (R +R )(R +R +R )-2a.h+h a.h a.pr h.pr a.h"

Dividing equation (10) by (11), we will obtain thecurrent short-circuited to the propeller

a.h a.pr Ra.h

i.e. when Ra.h>R a.pr+Rh.pr' most of the current will flow

to the propeller. When Ra.h=Ra.pr +R h.pr, the current

a.pr= Ia.h"

The expressions obtained in this study indicate thatthe equality between the contact corrosion current and theprotection current may be assumed as the approximatecondition for protection against corrosion. Hence, in orderto eliminate the propeller-hull voltaic couple and effectpropeller protection against corrosion, it would be neces-sary to install contact-brush devices.

53

Example: Calculate the current of the hull-propeller couple

on the ALATYR'LES motor ship.

1. The propeller leakage resistance1 1$ ,),Rle , .(' ,,; ohm;

2,33a; , ./ohm. m;, - 2.5 ra

J" .'D .s: -,--* I 1 ., . .9 ..

From the elliptic integral tables [2] we will determine

K(k) = 1.57; K(k') = 3.69.

2. The hull polarization resistance

Rh = 0.3/Spr = 0.3/16.6 = 0.018 ohm.

3. The internal resistance of a single bearing

... .I "*" " 'i I

4. The resistance of all bearings (8 journal-type and1 stern-type)

, -,

4. The total resistance

Rtot = 0.0077+0.018+0.0425 0.0682 ohm.

5. The shafting current

Ih.pr = UhUpr /Rtot = 5.9a.

Based on the measurements, the shafting current is 6.2awhile the internal resistance

Rin = tg"= U/I = 0.230/6.2 = 0.0371 ohm.

As may be seen, the calculated results are in fairlvgood agreement with the measurements.

54

REFERENCES

1. GUZEYEV, V.T. Determination of the ElectricalParameters of the Propeller-Shaft-Hull Systemand Their Practical Application. TRUDY TsNIIMFa(Transactions of the Central Scientific ResearchInstitute of the Maritime Fleet), No. 99.Leningrad. "TRANSPORT" Publishing House, ]968.

2. YANKE, E. and EMDE, F. TABLITSY FUNKTSIY S FORMULAMII KRIVYMI (Tables of Functions With Formulas andCurves). MOSCOW, "GOSTEKHIZDAT" PublishingHouse, ]948.

55

METHODS OF ACCELERATED CORROSION TESTINGOF ORGANOSILICON COATINGS

[By M. Ya. Rozenblyum and L. A. Suprun. In "Tekhnicheskayaekspluatatsiya morskogo flota. Teplokhimicheskiye issledo-vaniya. Bor'ba s korroziyey i obrastaniyem" (TechnicalOperati(Ws of the Maritime Fleet. Thermochemical Studies.Control of Corrosion and Fouling). Transaction of theCentral Scientific Research Institute of the Maritime Fleet.No. 160, 1972. "Transport" Publishing House, Leningrad, pp. 89-93Russian)

The capacitance-resistance method has been employed inmany cases [13] to determine the protective properties ofpaint-and-varnish coatings; the procedure permits nonde-structive quantitative evaluation of the coating. It hasbeen known that the capacitance of the coating increaseswhile its resistance decreases in the process of testingand destruction. An appropriate electric measuring circuitmust be used for the system under study, otherwise thedirect measurements would have to be recalculated to obtaintrue capacitance-resistance characteristics [2-3].

In the beginning of the test, when the coating isfairly continuous, the system being measured consists ofa capacitance and a resistance connected in parallel(parallel connection). As the coating begins to fail, itdevelops continuous pores where the measured cell becomesa series-connected capacitance-resistance system. Thecapacitance-resistance connection diagram is determinedfrom the frequency curve [3].

In these experiments involving the study of organo-silicon coatings by the capacitance-resistance method usingan R568 a-c bridge with a series connected capacitance andresistance at 1000-Hz frequencies and 30-mv operatingvoltages was initially found to increase to its maximum andthen drop. This growth rate of the resistance for an eitherconstant or increasing capacitance is probably related to thetransition from a parallel capacitance-resistance connectiondiagram of the coating to a series-connected circuit. It islikely that only when the coating's resistance reaches itsmaximum, then it becomes a series-connected circuit in whichthe measured resistance represents the electrolyte's resis-tance in the pores of the coating. After the maximum isreached and the resistance decreases, the coating exhibitsvisible traces of corrosion. Thus, the time interval re-quired for reaching maximum resistance characterizes thespecific type of coating and may, therefore, be used as its

56

stability criterion. If, however, one should calculatethe true resistance on the initial section of the curvewith the capacitance and resistance connected in parallel,then the resistance-versus-time curve would smoothlydescend with the typical signs of the onset of coatingfailure.

It has been known that tests can be accelerated bythe use of more aggressive environments, higher tempera-tures, increased aeration, reduced coating thicknesses,etc. Unlike other techniques, reduced coating thicknessesaccelerate coating failure without affecting the kineticsof the electrochemical process. The accelerated testswhich will be described below were, therefore, conductedon thin film. The organosilicon test varnish coatingsincluded K44, K47, and K54 grades; MgO, ZnO, A1203, TiO 2,

Cr203 , and Fe20 3 pigments and fillers. These test

materials were applied by pouring on the surface of St.3steel plates measuring 150x100x15 mm. Prior to painting,the metal surfaces were preconditioned by mechanicalcleaning and degreasing with toluene. After application,the coatings were dried at 200*C for 2 hours so that thefinal coating thickness was 15u. Glass cylinders, 35 mmin diameter and 50 mm high were filled with a 3% NaClsolution, to imitate sea water, were cemented to thepainted plates. The test data on the corrosion resistanceof the organosilicon varnishes are given in Figure 1.Based on the data obtained, K54 varnish was selected forfurther testing and used as a basis for compositions con-taining 5% of the said oxides (by volume); each compositioncontained only one type of pigment or filler.

Figure 2 shows test data on coatings containing ZnO,Cr203, and Fe20 3. Compositions with MgO, A1203 have not

been cited in this figure since their protective propertieswere much lower than those of K54. The curves in Figure3 show compositions with ZnO and Cr203 to have the higher

resistance (35 and 30 days, respectively). The resultsshown by the composition with Fe 203 were inferior to those

with the first two oxides.

The corrosion resistance study of compositions con-taining ZnO and Cr203 in amounts ranging from 0 to 30%

THIS

PAGEIS

MISSINGIN

ORIGINALDOCUMENT

Kb

filler concentration, %(vol

Figure 3. Effect of Filler Content on the CorrosionResistance of the Coating

(by volume) shows 5% (by volume) to be the optimum fillercontent in the K54 varnish (Fig. 3). The accelerated testdata have been summarized in a table. For comparison, thetable provides also long-term test data on the samecoating in thicknesses of about i0gA described in an earlierstudy [4]. As may be seen from the table, the first tracesof corrosion appeared only after maximum resistance hasbeen reached, while the diff-rence between the time ofappearance of initial corrosion traces and the testdurations, corresponding to maximum resistance (coatingstability) increases with the coating's thickness and itsstability. The stability value obtained with the acceler-ated procedure correlates well with those of long-termtests. The resistance of organosilicon coatings of about100* in thickness is 45-52 times higher than those of 15.The conversion factor obtained permits calculation ofcoatings containing Cr 2 03 and ZnO whose long-terms are yet

to be completed.

Conclusions

1. The study of organosilicon coatings in a 3% NaCIsolution by the capacitance-resistance method hasshown that the measured resistance rises (in thebeginning of testing) to its maximum with a slightincrease in capacitance after which it begins todrop while the capacitance rapidly rises.

59

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3. The results of accelerated corrosion tests on organo-silicon coatings correlate well with the data of long-term laboratory tests which indicates the feasibleapplication of accelerated testing procedures forselecting organosilicon coatings.

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