COLD GALVANIZING
CATHODIC PROTECTION

Questions ?
Le sujet

Cold galvanizing

Cold galvanisation is an organic, single-component zinc coating of minimum 92% (weight) zinc in the dry layer.

on Monday May 13 by M4nd3
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No, the cold galvanisation product is a single component. It requires no mixing with other chemicals to make it cure.

on Monday May 13 by M4nd3
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Yes, it does give the same lifetime expectation as hot dip galvanising. It last even 3 times longer under water.

on Monday May 13 by M4nd3
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The cold galvanising acts as an active coupling to the steel parent metal to form an electrolytic bond, which results in a potential of 1060mV.

on Monday May 13 by M4nd3
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The cold galvanising gives a cathodic protection up to a 4mm scratch, this surface will often show a light brown-grey colour.

on Monday May 13 by M4nd3
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Yes, the lifetime can be increased considerably by protecting the cold galvanisation with a top coating. Similar to the protection of hot dip galvanizing.
This is called a duplex system, a cathodic protection and a passive protection (a paint). This can increase the initial lifetime with 2 to 3 times the initial lifetime. (See graphic British Standards)

on Monday May 13 by M4nd3
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No, one can apply directly after hardening of the cold galvanizing the paint no special blasting is required. Curing time of the zinc layer is to be respected, see technical data sheet.

on Monday May 13 by M4nd3
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No, one should use a compatible paint. See technical data sheet or ask your supplier. Never apply petrol derivates e.g. tarred products.

on Monday May 13 by M4nd3
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Yes, but this doesn't make sense. Because there is no direct contact with the parent steel surface there will be no cathodic protection, the cold galvanisation will only give a passive paint protection.

on Monday May 13 by M4nd3
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Yes, because one can apply it in the paint shop with the same spraying equipment used for normal paints.

on Monday May 13 by M4nd3
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Yes, this is the only way of restoring the old cathodic protection of old hot-dip layers. The surface has to be cleaned from loose rust and dirt. A high-pressure water wash or steam cleaning will be sufficient as surface preparation.

on Monday May 13 by M4nd3
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No, cold galvanisation does not provide any fire protection. Nevertheless a dry cold galva layer will not propagate, cause or spread a fire.
A compatible intumescing topcoat is the solution.

on Monday May 13 by M4nd3
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Yes, cold galvanisation will provide an excellent mechanical property; it has been used for Ro Ro terminals, chains, jetty's and machinery. The resin that hold the zinc allows the zinc to "move" with the structure without cracking nor peeling off. It will resist extreme distortion.

on Monday May 13 by M4nd3
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Yes, on 40μm one can easily make the welds. On 40μm one can make normal welds with rods or MIG with X-ray quality can be done without porosities. Cold galvanisation can therefore be used as shop and welding primer and later on increased to a full 80μm cathodic protection.

on Monday May 13 by M4nd3
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Yes, after High Pressure water jet cleaning you can apply cold galvanisation without the need for complete drying of the surface.

on Monday May 13 by M4nd3
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No, you don't have to do so. It certainly gives a good result, because it improves the polymerisation and the formation of zinc salts and zinc carbonates on the surface and this offers a barrier protection with a harder coating.
It also helps to avoid dark spots on the freshly coated surface due to raindrops.

on Monday May 13 by M4nd3
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The most economical surface preparation and also the most environmental friendly one is the Ultra High Pressure (4.000 bar) water cleaning with the use of Almandite Garnet as abrasive.

on Monday May 13 by M4nd3
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