Letter 19064

Under coat require for hard chrome on steel for severe marine atmosphere [India] 

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Dear sir,

We are a metalfinishing chemical supplying house in India. We are interested to know the under coat for hard chrome plating on carbon steel/SS304 which can withstand in sea water.The component are used for drilling oil & gas in offshore plateform. Kindly give the guidelines which undercoat is most suitable under this severe corrosive condition.Also indicate coating thickness of undercoat.

We have already tried with nickel(150 micron)+new generation chrome 150 micron(microcrake chrome) & different heavy thickness of S.B nickel+chrome (micro craked) but failed to withstand .Requirement is two months withstand.

Thank you,

Partha Das
- India

Better than nickel would be electroless nickel but it is difficult to apply chrome on top of it, specially thick hard chrome. Have you checked the porosity of your first nickel layer? It sounds like 150 microns (0.006") of pore free nickel should be enough. Another posibility, if scratch or impact resistance is not a problem, would be to start with alkaline copper (25-50 microns) then acid copper (25-50 microns) then your nickel+chrome plating.

Guillermo Marrufo
Monterrey, NL, Mexico

Yes it can be tricky, But not hard, as with most plated deposits. It's what your process is and how you process your parts. You may have to find the correct activator or dwell times or the like.

Chris Snyder
- Charlotte, NC

Interesting. I understand using copper as an undercoat, but why acid and alkali copper. Is it not pretty much the same once it's deposited?

Ian Brooke
- Scotland

"Copper Deposit" is not the same after plating, grain structure, deposit hrdness, and co deposits are very much diffrent Example acid copper plating for carbonizing mask will not work

Chris Snyder
- Charlotte, NC

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