A Longer Life
SACRIFICIAL ANODES
Hull Anodes
Bolt-on Anodes / Disc Anodes
Tank Anodes
Pitguard Anodes
Pencil / Rod Anodes
Mounting Material
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Page: CONTENTS:
2
Alloy specification of standard sacrificial anodes
3
Choosing zinc or aluminium anodes
4
Anode recommendations
5
Choosing tank anodes
7 - 28 WELD-ON HULL ANODES
Aluminium weld on hull anodes
30 - 46 Zinc weld on hull anodes
BOLT-ON ANODES / DISC ANODES
48 - 58
Aluminium bolt on hull anodes (with 2 bolting holes)
60 - 70 Zinc bolt on hull anodes (with 2 bolting holes)
72 - 77 Aluminium bolt-on disc anodes (with 1 bolting hole)
79 - 86 Zinc bolt-on disc anodes (with 1 bolting hole)
TANK ANODES
88 - 101 Aluminium tank anodes
103 - 116
Zinc tank anodes
PITGUARD ANODES
118 - 121 Aluminium pitguard anodes (including 1 clamp per anode)
123 - 127
Zinc pitguard anodes (including 1 clamp per anode)
PENCIL / ROD ANODES
129
Zinc pencil anodes + brass plugs for pencil anodes
131
Zinc rod anodes (solid / massive zinc anode bar, excl. holes, excl. insert)
MOUNTING MATERIAL
133
Stud assembly for bolt-on anodes
134 “M”-clamp installation for tank anodes in general
135 “M”-clamps for tank anodes (2 clamps per anode required)
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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 Zinc (Zn) Titanium (Ti) Silicon (Si) Bismuth (Bi) Indium (In) Copper (Cu) Iron (Fe) Others each Aluminium
Range (%)
3.50 - 5.00
0.01 - 0.05
0.05 - 0.20
0.05 - 0.15
0.02 - 0.05
0.01 max
0.15 max
0.10 max
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
Aluminium (Al) Cadmium (Cd) Copper (Cu) Iron (Fe) Lead (Pb) Others total Zinc (Zn) Nominal electrical capacity: Nominal open circuit potential:
Range (%)
0.10 - 0.5
0.025 - 0.07
0.005 max
0.005 max
0.006 max
0.10 max
Balance
780 AmpHr/Kg
-1050 mV vs Ag/AgCl (seawater) reference cell
The copper, iron and lead contents of our normal zinc alloys are usually less then 0.003%
each.
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‘A LONGER LIFE’
CHOOSING ZINC OR 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) the 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 is considered to be less neutral to the
environment.
For anodes used in water ballast and other tanks see chapter “Choosing tank anodes”
(page 5).
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‘A LONGER LIFE’
ANODE RECOMMENDATIONS
Saltwater
Zn
Al
Mg
In saltwater, both Zinc and Aluminium are suitable, but aluminium has a better re-activation
performance.
Brackish Water
Zn
Al
Mg
Aluminium is the recommended material for brackish water.
Fresh Water
Zn
Al
Mg
On pure fresh water magnesium is the best performing anode material.
With polluted water or when a boat is temporary in brackish water, aluminium is the preferred
anode.
The recommendations apply to steel structures. For more detailed information, please
consult your local distributor.
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‘A LONGER LIFE’
CHOOSING TANK ANODES
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 societies 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 conductivity
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 (see page 122).
For the pros and cons of the use of zinc or aluminium alloys for sacrificial anodes used
see chapter “Choosing zinc or aluminium as alloy for sacrificial anodes” (page 3).
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‘A LONGER LIFE’
ALUMINIUM
WELD-ON
HULL ANODES
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ZINC
WELD-ON
HULL ANODES
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ALUMINIUM
BOLT-ON
HULL ANODES
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ZINC
BOLT-ON
HULL ANODES
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MME 24ZB
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ALUMINIUM
BOLT-ON
DISC ANODES
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ZINC
BOLT-ON
DISC ANODES
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ALUMINIUM
TANK ANODES
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ZINC
TANK ANODES
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ALUMINIUM
PITGUARD ANODES
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ZINC
PITGUARD ANODES
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ZINC
PENCIL ANODES
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ZINC
ROD ANODES
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MOUNTING MATERIAL
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MME Group has a large, professional and fully owned
foundry for the manufacturing of sacrificial anodes for the
marine, offshore, renewable energy and civil engineering industries.
Leading through
more than 50 years
of know-how
and experience
Other MME products
and services
MME Group
Rietdekkerstraat 16
PO Box 4222
2980 GE Ridderkerk
The Netherlands
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Gangways
T: +31 (0)180 48 28 28
F: +31 (0)180 46 22 41
E: sa@mme-group.com
I: www.mme-group.com
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