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Electrogalvanizing of cable trays on ships [India] 

September 10, 2009

What is the minimum zinc coating thickness required on cable trays in the engine room spaces onboard Ships.

I am heading a new build project in India. The cable ladders / hangers have a Zinc coating of about 4-10 microns and the Shipyard says that's fine. I am unable to get any inputs for this from any standards that I could get my hands on. But I remember having read somewhere, a long time ago, that for marine applications, the zinc electroplating should have a thickness of about 25 microns. I therefore need some authentic inputs/documentary proof to put across my point of view. That's the situation. Best Regards,

Ramesh Pillai
user - India

Hi, Ramesh. Unfortunately, I don't know if there are any controlling specifications for ship-board cable trays. But I do believe that, while 4-10 microns would be adequate for a land-based cable tray inside a building, it's seems awfully thin for the salty, corrosive environment of a ship.

An additional problem is probably that 25 microns is a thickness that would require real galvanizing, i.e., hot dip galvanizing, and would not be practical with zinc electroplating -- I don't like to use the word "electrogalvanizing' and find it a deliberately obfuscatory term, because zinc electroplating is not an adequate substitute for galvanizing, whereas that term makes it sound like it is :-)

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey