123588029 Galvannealed Ga Galvanealed Zinc Fe Zinc Ro Zinc Iron Alloy a Practical Study
Page: CONTENTS: HULL ANODES BOLT-ON ANODES / DISC ANODES ... Sacrificial... · 2. The use of zinc /...
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Page: CONTENTS: 1 Alloy specification of standard sacrificial anodes 2 Use of zinc or aluminium anodes 3 Use of sacrificial anodes in tanks HULL ANODES 4 – 23 Aluminium hull anodes 24 – 40 Zinc hull anodes BOLT-ON ANODES / DISC ANODES 41 – 49 Aluminium hull bolt-on anodes (with 2 bolting holes) 50 – 58 Zinc hull bolt-on anodes (with 2 bolting holes) 59 – 64 Aluminium bolt-on disc anodes (with 1 bolting hole) 65 – 72 Zinc bolt-on disc anodes (with 1 bolting hole) TANK ANODES 73 – 86 Aluminium tank anodes 87 – 99 Zinc tank anodes PITGUARD ANODES 100 – 103 Aluminium pitguard anodes (including 1 clamp per anode) 104 – 108 Zinc pitguard anodes (including 1 clamp per anode) PENCIL / ROD ANODES 109 Zinc pencil anodes + brass plugs for pencil anodes 110 Zinc rod anodes (solid / massive zinc anode bar, excl. holes, excl. insert) MOUNTING MATERIAL 111 “M”-clamps for tank anodes (2 clamps per anode required) 112 Stud assembly for bolt-on anodes
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Transcript of Page: CONTENTS: HULL ANODES BOLT-ON ANODES / DISC ANODES ... Sacrificial... · 2. The use of zinc /...
Page: CONTENTS:
1 Alloy specification of standard sacrificial anodes
2 Use of zinc or aluminium anodes
3 Use of sacrificial anodes in tanks
HULL ANODES
4 23 Aluminium hull anodes
24 40 Zinc hull anodes
BOLT-ON ANODES / DISC ANODES
41 49 Aluminium hull bolt-on anodes (with 2 bolting holes)
50 58 Zinc hull bolt-on anodes (with 2 bolting holes)
59 64 Aluminium bolt-on disc anodes (with 1 bolting hole)
65 72 Zinc bolt-on disc anodes (with 1 bolting hole)
TANK ANODES
73 86 Aluminium tank anodes
87 99 Zinc tank anodes
PITGUARD ANODES
100 103 Aluminium pitguard anodes (including 1 clamp per anode)
104 108 Zinc pitguard anodes (including 1 clamp per anode)
PENCIL / ROD ANODES 109 Zinc pencil anodes + brass plugs for pencil anodes
110 Zinc rod anodes (solid / massive zinc anode bar, excl. holes, excl. insert)
MOUNTING MATERIAL 111 M-clamps for tank anodes (2 clamps per anode required)
112 Stud assembly for bolt-on anodes
MATERIAAL METINGEN EUROPE B.V. P.O. Box 4222 - 2980 GE Ridderkerk (the Netherlands)
ALLOY SPECIFICATIONS OF STANDARD SACRIFICIAL ANODES
GENERAL The below mentioned alloys have been chosen with great care to ensure an even corrosion pattern, reliable electrical capacity and a long working life. These alloys are used for standard sacrificial anodes. On request Materiaal Metingen Europe can cast anodes with different alloy specifications.
ALUMINIUM ALLOY
Element Range (%)Zinc (Zn) 3.50 - 5.00 Titanium (Ti) 0.01 - 0.05 Silicon (Si) 0.05 - 0.20 Bismuth (Bi) 0.05 - 0.15 Indium (In) 0.02 - 0.05 Copper (Cu) 0.01 max Iron (Fe) 0.15 max Magnesium (Mg) - Lead (Pb) - Cadmium (Cd) - Others each 0.10 max Aluminium Balance
Nominal electrical capacity: 2700 AmpHr/Kg Nominal open circuit potential: -1100 mV vs Ag/AgCl (seawater) reference cell
ZINC ALLOY acc. US MIL Spec. A-18001K
Element Range (%)Aluminium (Al) 0.10 - 0.5 Cadmium (Cd) 0.025 - 0.07 Copper (Cu) 0.005 max Iron (Fe) 0.005 max Lead (Pb) 0.006 max Silicon (Si) - Titanium (Ti) - Bismuth (Bi) - Indium (In) - Magnesium (Mg) - Others total 0.10 max Zinc (Zn) Balance
Nominal electrical capacity: 780 AmpHr/Kg Nominal open circuit potential: -1050 mV vs Ag/AgCl (seawater) reference cell
The copper, iron and lead contents of our normal production alloy are usually less then 0.003% each.
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MATERIAAL METINGEN EUROPE B.V. P.O. Box 4222 - 2980 GE Ridderkerk (the Netherlands)
ZINC VERSUS ALUMINIUM AS ALLOY FOR SACRIFICIAL ANODES
GENERAL Traditionally many companies prefer to use zinc instead of aluminium. MME advices the use of aluminium instead of zinc for the following reasons:
1. Price of anode material
Due to the fact that the capacity of aluminium (2700 A hr/Kg) is almost 3.5 times higher than zinc (780 A hr /Kg) tot total amount of required anode material (Kg) is less. This results in a cheaper Cathodic Protection System to that given by zinc with an equal level of protection.
2. Price of Installation
As the total weight of anode material for a system using aluminium is less compared to a system using zinc anodes the installation costs for a system using aluminium anodes will also be less.
3. Multi Effective
In brackish water aluminium anodes work more effectively than zinc, due to the higher driving voltage of aluminium.
4. Environmental Pollution
Compared to aluminium alloys, zinc alloys contain more elements which are detrimental for the environment.
For anodes used in water ballast and other tanks see chapter The use of sacrificial anodes in tanks
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MATERIAAL METINGEN EUROPE B.V. P.O. Box 4222 - 2980 GE Ridderkerk (the Netherlands)
THE USE OF SACRIFICIAL ANODES IN TANKS
GENERAL Traditionally many vessels are fitted with sacrificial anodes for external protection (hull). For achieving the same protection of the internal construction of the vessel (mainly water ballast tanks) sacrificial anodes can also be used. However due to the fact that tanks are inherently complex structures as well as being confined spaces the use of anodes has to be well engineered and the following rules adhered to.
1. Effect of ballast tank anodes
The ballast tank anodes will be without effect when the ballast tanks are empty. It will take some time to obtain full effect (polarisation) of submerged steel surfaces after filling with seawater. In the ullage space or under deck area on top of tanks the anodes will not be effective unless the tank is completely filled.
2. The use of zinc / aluminium or magnesium alloy anodes
Anode alloy materials based on zinc or aluminium are acceptable, magnesium alloy is not allowed. Ballast tanks adjacent to tanks for liquid cargo with a flash point < 60 C are to be considered as dangerous areas. Aluminium alloy anodes are to be located in such way that the kinetic energy which is developed in case of loosening and falling down will be < 275 J. This means that in these areas the maximum height (in mtr) of an aluminium anode above tank bottom, deck or stringer may not exceed the value obtained by "28 / W", where "W" is the gross weight of the anode. Furthermore classification society may require structures to be installed to protect the aluminium anodes from being hit by falling objects. Please consult your local surveyor / classification society branch office for full details.
3. Welding or bolting type anodes
For a good operation of the anodes it is vital to have a good electrical continuity between the ship structure and the anodes. This can be obtained either by welding (preferably) or bolting the anodes to the ship structure. In case bolting type anodes are requested the optional "M" clamps can be used.
For the pros and cons of the use of zinc or aluminium alloys for sacrificial anodes used see chapter Zinc versus aluminium as alloy for sacrificial anodes
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