Founded 1945 CORROSION SCIENCE - Cortec Corporation of Science.pdfFounded 1945 CORROSION SCIENCE 515...

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Vol. 60, No. 6 June 2004 Founded 1945 CORROSION SCIENCE 515 523 538 548 561 2004 F.N. Speller Award Lecture: Efficacy of Vapor Phase Corrosion Inhibitor Technology in Manufacturing B. Miksic, R. Boyle, and B. Wuertz Corrosion Mechanism of Nickel-Containing Stainless Steels in Concentrated Aqueous Solutions of Sulfuric Acid J.R. Kish, M.B. Ives, andJ.R. Rodda Detecting External Failures in Coated, Buried Pipelines: Theoretical Model and Experimental Verification H. Castaneda and M. Urquidi-Macdonald Corrosion Evaluation of Alloy 800 in Sulfate/Vanadate Molten Salts C. Cuevas-Arteaga, J. Uruchurtu-Chavan'n, J. Gonzalez, G. Izquierdo-Montalvo, J. Porcayo-Calderon, and U. Cano-Castillo Electrochemical Study of UNS S32550 Super Duplex Stainless Steel Corrosion in Turbulent Seawater Using the Rotating Cylinder Electrode G. Kear, B.D. Barker, and F.C. Walsh CORROSION ENGINEERING 573 584 594 Microstructural Characterization and Pitting Corrosion Behavior of UNS S30466 Borated Stainless Steel D.A. Moreno, B. Molina, C. Ranninger, F. Montero, and J. Izquierdo Effect of Climatic Parameters on Filiform Corrosion of Coated Aluminum Alloys N. LeBozec, D. Persson, D. Thierry, and S.B. Axelsen Development of an Artificial Saliva Solution for Studying the Corrosion Behavior of Dental Alloys G.S. Duff6 and E. Quezada Castillo

Transcript of Founded 1945 CORROSION SCIENCE - Cortec Corporation of Science.pdfFounded 1945 CORROSION SCIENCE 515...

Page 1: Founded 1945 CORROSION SCIENCE - Cortec Corporation of Science.pdfFounded 1945 CORROSION SCIENCE 515 523 538 548 561 ... packaging, process industries, reinforced concrete, coatings,

Vol. 60, No. 6 June 2004

Founded 1945

CORROSION SCIENCE

515523538548561

2004 F.N. Speller Award Lecture: Efficacy of Vapor Phase Corrosion InhibitorTechnology in ManufacturingB. Miksic, R. Boyle, and B. Wuertz

Corrosion Mechanism of Nickel-Containing Stainless Steels in ConcentratedAqueous Solutions of Sulfuric AcidJ.R. Kish, M.B. Ives, andJ.R. Rodda

Detecting External Failures in Coated, Buried Pipelines: Theoretical Modeland Experimental VerificationH. Castaneda and M. Urquidi-Macdonald

Corrosion Evaluation of Alloy 800 in Sulfate/Vanadate Molten SaltsC. Cuevas-Arteaga, J. Uruchurtu-Chavan'n, J. Gonzalez, G. Izquierdo-Montalvo,J. Porcayo-Calderon, and U. Cano-Castillo

Electrochemical Study of UNS S32550 Super Duplex Stainless Steel Corrosionin Turbulent Seawater Using the Rotating Cylinder ElectrodeG. Kear, B.D. Barker, and F.C. Walsh

CORROSION ENGINEERING

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584594

Microstructural Characterization and Pitting Corrosion Behavior of UNS S30466Borated Stainless SteelD.A. Moreno, B. Molina, C. Ranninger, F. Montero, and J. Izquierdo

Effect of Climatic Parameters on Filiform Corrosion of Coated Aluminum AlloysN. LeBozec, D. Persson, D. Thierry, and S.B. Axelsen

Development of an Artificial Saliva Solution for Studying the Corrosion Behaviorof Dental AlloysG.S. Duff6 and E. Quezada Castillo

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2004 F.N. Speller Award Lecture:Efficacy of Vapor Phase Corrosion InhibitorTechnology in Manufacturing

R. Boyle, * and B. Wuertz*

ABSTRACT

Corrosion is a plight that faces everyone who works withmetals. Its impact on the U.S. economy has been documentedto be about 4% of the gross national product. It was esti-mated that about one third of the corrosion damage could beavoided. The avoidable costs were related to the failure touse the best practices available. There are several ways ofcombating corrosion. One way that is gaining wider accep-tance is to use vapor phase corrosion inhibitors. Volatile cor-rosion inhibitors were originally developed to protect boilersand piping systems of ships to be mothballed. Their effective-ness and ease of application attracted early users. Over theyears, the field of usage has increased to cover electronics,packaging, process industries, reinforced concrete, coatings,and metalworking fluids.

KEY WORDS: vapor phase corrosion inhibitors, manufactur-ing, metals

INTRODUCTION

A 2002 NACE International study estimated that theannual cost of corrosion in the United States alonenears 3.1% of the gross domestic product (GDP)—astaggering $340 billion. The real-world implication tometal manufacturing and processing is the addedcost of doing business. Aside from the most visibleeffects, such as product failure and rejection, arethose "hidden" costs that are part of the everyday

Presented as the F.N. Speller Award Lecture at CORROSION/2004, March 2004, New Orleans, LA.Corresponding author.Cortec Corporation, 4119 White Bear Parkway, St. Paul, MN55110.

manufacturing process. Expenditures on cleaning,blasting, reworking, and disposal combined withlabor-intensive additional processing steps greatlyaffect the bottom line.

To combat the devastating effects of corrosionand in an attempt to preserve valuable militaryequipment, the U.S. Navy tested the first volatile cor-rosion inhibitor (VCI) chemistry for the mothballingof boilers and similar structures on war ships in thelate 1940s. The core chemistry at that time was atoxic amine nitrite solution applied to the inside ofinaccessible spaces. Although a similar nitrite-basedchemistry is still widely used today, there is an effec-tive, environmentally sound, and safer alternative.(Figure 1).

A new generation of corrosion inhibitors emergedin the late 1970s called vapor phase corrosion inhibi-tors (VCIs). These new chemistries were developed toutilize state-of-the-art, nontoxic organic inhibitors ina wide variety of forms. The VCI technology, as de-scribed below, protects metals from corrosion duringmanufacturing, processing, shipping, storage, andwhile in use without any residual contamination tothe protected metal. The result is a vast line of prod-ucts all designed to take the cost of corrosion out ofthe metalworking and manufacturing process.

CORROSION AND VCIs

Simply defined, corrosion is the natural processof a material, usually a metal, returning to its origi-nal state through an electrochemical process due toa reaction with the surrounding environment. Al-

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Toxicity DataChemical LD50 (mg/kg-rat)

Table salt 3,000(sodium chloride)

Food preservative/corrosion inhibitor 85(sodium nitrite)

Nitrite-based VCI powder 284

Non-nitrite-based VCI powder 2,100

FIGURE 1. Toxicity data for some common corrosion inhibitors.

Molecules ofVCt in gaseous phase

FIGURE 2. VCI molecules vaporize, condense on all metal surfaces,and re-heal and self-replenish through further condensation of thevapor.

though corrosion is a natural process, certain atmo-spheric conditions that a metal is exposed to duringits manufacture, processing, storage, or shipmentcan aggressively accelerate the degradation. Mostnotable of these factors are sulfur dioxide (typicallyassociated with the burning of coil, oil, and gas),acids in packaging materials, and temperature andhumidity fluctuations during transit.

VCIs are organic compounds that have sufficientvapor pressure under ambient atmospheric condi-tions to travel essentially to the surface of the metalby diffusion and to adsorb physically onto the sur-face. In the presence of moisture, the VCI moleculebecomes polarized and attracted to the anode andcathode of the metal. Once the VCI protective ionsare adsorbed onto the surface, the electrochemicalprocess of corrosion is interrupted as the ions createa protective barrier to contaminants such as oxygen,

water, chlorides, and other corrosion accelerators.With the protective barrier in place, the corrosion cellcannot form and corrosion is halted. (Figure 2).

Unlike nitrite inhibitors, which do not havesufficient vapor pressure under ambient conditions,VCI products can actually protect yellow and ferrousmetals as well as soldered parts and alloys. Whereaswater-displacing, water-absorbing, dehumidification,and barrier products try to alter an ever-changingenvironment surrounding the metal, VCI technologypassivates the metal's surface. In fact, VCI moleculesactually use the same mechanism that acceleratescorrosion to accelerate the release of protection mol-ecules—a built-in defense mechanism (Figure 3).

MANUFACTURING WITH VCI PRODUCTS

During the typical manufacture of a metal prod-uct, the material is cleaned, oiled, blasted, machined,finished, assembled, painted, and packaged—in somecases, numerous times before it is sent to the cus-tomer. By effectively utilizing the benefits of VCItechnology, many of these in-process steps can becompleted eliminated (Figure 4). Other cost savingsresult when the disposal and cleanup costs are cal-culated. Imagine a manufacturing process where thestarting metal structure is processed without needfor secondary oil rust preventatives, rework, rustremoval, blasting, or cleaning.

VCIs in their pure form are usually off-whitepowders and can be used in this form for protectionof large void spaces (such as the heat recovery steamgenerators [HSRGs], boilers, turbines, and pipespreviously coated with amine nitrite inhibitors). Addi-tionally, VCIs can be incorporated into coatings,greases, functional fluids, cleaning systems, hydro-testing solutions, even concrete and plastics. Theresult for a manufacturer utilizing VCI product isstreamlined processes, improved product quality andacceptance, and overall cost reduction.

But how do VCI molecules affect the metal sur-face? The VCI molecules are designed specifically toprevent reactions on the metal surface. Whereasmany methods of corrosion protection alter the metal(i.e., stainless vs carbon steel, cathodic protection,and treatment of metal), VCIs do not alter the surfaceas the protective ions are adsorbed to the surfacerather than becoming permanently attached.

A study was conducted on VCI products todetermine how the protective molecules affected theexposed ends of fiber optics cables. Three productswere tested, including VCI-treated anti-stat polyeth-ylene film, polyurethane foam impregnated with VCI,and VCI powder contained in high-density vapor per-meable polyethylene film pouches. The testingshowed that there was no indication of attenuationchange caused by the corrosion inhibitors. The re-sults of this study are included in Figure 5.

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Corrosion Prevention Methods Used by Military OrganizationsCorrosionPrevention

Method Product Type Benefits Disadvantages

Water-displacing products Petroleum-based(light oils or thixotropicgreases)

Water-absorption products Silica gel (dessicants)

Dehumidification • Dehumidifier• Vapor barrier bags

VCIs • Anodic inhibitors (e.g.,sodium nitrite [NaNO2],dicyclohexylamine nitrite,sodium benzoate)

• Cathodic inhibitors• Mixed inhibitors

• Relatively inexpensive• Water displacement• Create a barrier coating on

metal surfaces• Excellent permanent protection

• Economical alternatives fortemporary protection

• Effective for storage andshipping

• Effective in electronic andelectrical operations

• Can be successful if air flow tothe metal is totally restricted

• Vapor barrier bags areexcellent for one-time use (offera sturdy multilayer film)

• Good way to protect electronics

• Anodic inhibitors> Prevent metal corrosion

• Cathodic inhibitors> Slow cathodic reaction> Precipate onto cathodic sites,

restricting diffusion of corrosivespecies

• Mixed inhibitors> Adsorbed onto metal surface,

creating a monomolecular layer> Monomolecular film acts as a buffer,

maintaining pH at optimum range forcorrosion resistance

> Provide a universal effect oncorrosion process

• Costs increase with additives(e.g., contact inhibitors, extreme-pressure additives) needed toenhance protection

• High labor and material costs forapplication and removal ofproduct

• Use of solvent-based cleanersfor product removal makesthese products unsafe for theworker and environment

• Difficult to calculate specificmoisture that will be present(i.e., requires more dessicant andinspection)

• Costs increase with the additionof more dessicant and inspections

• Airtight seal is required butdifficult and expensive to achieve

• Dehumidifier> Electricity mandatory for

dehumidifier and not availablein remote locations

> Difficult to keep a seal on themetal object

> High cost of equipment andassociated upkeep

• Vapor barrier bags> High costs of materials and

labor needed to create air-tight protection

> Not a good method to useduring operations

• Anodic inhibitors> Negative effect on worker

safety> Negative effect on

environment

FIGURE 3. Advantages and disadvantages of different methods of preservation utilized by military organizations.

PROVING VCI EFFECTIVENESS

While there are many methods to test corrosioninhibiting compounds and methods, the industrystandards involve three principle criteria—contactprotection, vapor protection, and protection in simu-lated environments. There are standardized and in-dustry-accepted tests for each.

First, will the compound inhibit corrosion whenit is in direct contact with the metal it is designed toprotect? The "Razor Blade" test is a quick laboratorytest with a pass or fail rating—if corrosion exists af-ter the set time frame, the product fails. This test es-sentially tests the contact corrosion inhibiting abilityof a material. In most cases, the test is conducted ontest coupons and on multiple types of metal.

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FIGURE 4. Flow charts for manufacturing that utilizes and does not utilize VCI coating compounds.

Test specimen -

Enlarged view of "F"

A - Water retainer—Aluminum tube11.4 cm in length, 1.6 cm OD,and 1.3 cm ID. The tube shallhave a capacity of 16 ml distilledwater at 24 ± 2°C

B - Rubber stoppers—Two no. 61.3-cm rubber stoppers with a1.3-cm hole bored throughcenters

C - Jar lids—Plastic screw-type lid,with 3-cm holes drilled throughthe center with two 0.6-cm holes2.5 cm apart near the edge.

D - Jars—1-L size, mouth size6 cm diameter, 17.7 cm inheight, 13.6cm ID.

E - Insulating sleeve—1.3-cm IDrubber tubing, length 3.8 cm.

F - Steel specimen—1.6-cm OD,1.3 cm long with 0.9-cm-deepflat bottom hole drilled in center(0.8-cm wall cup).

(a)

FIGURE 5. (a) Standard setup for Federa! Standard 101c, GermanVIA test, (b) Results of the Federal Standard.

Second, Federal Standard lOlc, the German VIAtest, is used to determine if a corrosion inhibitingcompound will protect a metal when the compoundis never in contact with the metal. For this test, thecorrosion inhibiting compound is placed ina glass jar. A metal slug is placed in a rubber gasketattached to the lid, so it is prevented from coming incontact with the corrosion-inhibiting product.

Figure 5 details the results of the German VIAtest for polyethylene film containing VCI formultimetal protection compared to a nitrite-basedflexible packaging film. The results are measured ona scale from 0 to 3 (0 = worst protection, 3 = bestprotection), which detail the severity of corrosion onthe metal plug. Since nitrite-based inhibitors lacksufficient vapor pressure under ambient conditions,the products typically do not pass the German VIAtest, nor does the corrosion inhibitor travel to themetal.

Rochester Institute of Technology conductedextensive testing on several VCI products includingnitrite-based technologies used by Daubert, NorthernTechnologies, Aicello, SKS, as well as barrier filmproduced by Intercept and non-nitrite VCI productsmanufactured by Cortec Corporation. The results ofthese tests are shown in Figure 6.

Simulating environments through ASTM D 1748Humidity, ASTM Bl 17 Salt Fog, and ASTM D 53Prohesion also can be an effective means of evaluat-ing the comparative corrosion protection ability ofVCI products. These tests accelerate the corrosionprocess by placing the metal samples (either couponsor actual parts) in environmental chambers whereatmospheric conditions are monitored and altered.Figure 7 details the comparative results of severalVCI products under these tests (Figures 7[a] through[c]).

Many VCI products also have industry approvalsfor use in highly restrictive markets, such as directand indirect food contact. Polyethylene film contain-

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(b)

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(d) (e)FIGURE 6. Independent laboratory test results for: (a) carbon steel razor blade test, (b) copper razor blade test, (c) steelrazor blade test, and (d) Federal Standard 101c, German VIA test, (e) Cross reference chart for nitrite vs non-nitrite VCIinhibitors.

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(a)

(b)

(c)

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FIGURE 7. (a) Wax, with and without VCI. Test according to ASTM V-117. (b) The addition of VCI materials to a traditionalcoating greatly improved performance in ASTM B-117. (c) ASTM B-117 testing of grease with and without VCI additivepackage.

ing VCI for multimetal protection, for example, isideally suited for the shipment and storage of foodprocessing equipment and has indirect food contactapproval from the U.S. Federal Drug Administration(FDA). Water-based temporary coatings containingVCI for multimetal protection has U.S. Departmentof Agriculture (USDA) approval for use on packagingmaterial that is in direct contact with meat or poultryfood products. Both approvals, as well as many oth-ers, are evidence that VCI technology can provide acost-effective method of superior corrosion protectionwhile remaining nontoxic, safe for workers, and with-out affecting the surface of the protected metal.

EXAMPLES OF VCI PRODUCTS IN USE

A large telecommunications equipment manufac-turer was shipping high-value enclosures overseasusing barrier film, desiccant, vacuum seal, and hu-midity cards yet they were still experiencing nearly85% failure rate due to corrosion. Not only was theirpackaging and rust preventative method extremelyexpensive, an even higher cost was borne when theequipment had to be replaced. Additionally, thepackaging was compromised when customs offerswere forced to open the barrier film to inspect theenclosures.

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(a)

(c)

(b)

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Initial shipments were established using onlyVCI emmitting devices (seen as the small green cupattached to the right side of the enclosure in Figure8) and polyethylene film containing non-nitrite-basedVCIs. This polyethylene film contains VCI moleculesthroughout the film and is translucent allowing easycustoms inspection. The VCI emitting device quicklysaturate the enclosure with the protective corrosioninhibiting vapor allowing rapid shipments.

After switching to VCI products, this manufac-turer was able to eliminate all corrosion claims whilereducing costs by nearly 60%, including a decreasein material and labor costs.

The U.S. Air Force also has effectively used VCItechnology as part of its war readiness and equip-ment preservation methods. Vehicles that previouslywould have taken nearly a week to clean, drain, reas-semble, and operate are now wrapped in co-extrudedshrink film containing corrosion inhibitors, flameretardants, and UV inhibitors, with only the antennaand battery removed. All fluids in the vehicle, includ-ing brake, hydraulic, engine, and coolant, incorpo-rate a VCI additive to the existing fluid. The VCIadditive protects even after the oil or fluid has settledinto the reservoir, as detailed in Figure 9.

A large Power Generation OEM manufacturestheir heat recovery steam generators (HRSGs) inSouth East Asia. Historically, these units would be

FIGURE 8. A large piece of telecommunications equipment that wasbeing packaged for shipment utilizing VCI technology.

FIGURE 9. Pipeline section showing active vapor phase corrosion inhibitors at the liquid phase, the vapor phase, theinterface, and partition and emulsion barriers.

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full of corrosion upon arrival to their customer's sitedue to long shipping periods and large temperatureand humidity fluctuations. Several years ago, theyswitched to VCI products to protect the high-valuegenerators in transit as well as decrease cost andenvironmental impact.

United Space Alliance has utilized VCI technol-ogy successfully in the form of a water-based high-performance rust preventative for rocket boosterstructural components on National Aeronautics andSpace Administration (NASA) rockets. The importantfactors for NASA included rust prevention, cleanli-ness, ability to topcoat, and the VCI product couldnot negatively affect the metal surface. The VCI coat-

ing is applied to virtually all space rocket booster(SRB) structural components and can be used forsome limited flight applications.

CONCLUSIONS

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Corrosion costs industry billions annually and theeffects on a manufacturing facility can be cata-strophic if proper methods of prevention are not uti-lized. VCI products offer users an effective methodof protection while maintaining strict adherence toproduct quality, environmental considerations,worker safety, and even throughput and thebottomline.