Metal finishing Q&As since 1989

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Need heat treated parts plated for resistance to 10% nitric acid wash

I NEED A PLATING THAT WILL WITHSTAND A 10% NITRIC ACID WASH . PARTS ARE 1045 MATL HEAT TREATED TO 40-43 RC.

RAY EGAN
MACHINE SHOP - CHICAGO, Illinois, USA
2003

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First of two simultaneous responses --

A high P electroless nickel will stand up to 10% nitric for quite a while, but it will gradually be attacked. A good nickel-nickel-chrome finish could last for a long time, especially if it were a thick microcracked chrome vs a macrocracked chrome. I think that you would have stood a better chance with something like a heat treated 17-4 PH steel. There are also better "stainless" that are heat treatable and with good corrosion resistance, but cost and machineability are definite issues.

James Watts
- Navarre, Florida
2003

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Second of two simultaneous responses --

Chromium and aluminum are two common metals that resist attack by nitric acid at various concentrations. Aluminum cannot be readily plated, but chrome plating will do the job provided there are no chlorides or other halides in the solution. Only problem is the poor throwing power of this plating. If your parts have intricate surfaces, chrome covering might not be satisfactory.

Guillermo Marrufo
Monterrey, NL, Mexico
2003

A hard chrome plating without macro cracks is the best solution.

Michael Hekli
Switzerland
2003

I need a plating/coating that will withstand a 10% nitric acid wash. The parts are 1045 material hardened to 40-45 R "C" threaded i.d. rings spring steel from 1/2"-- 1 1/2".The plating must be ductile & compatible with installation on 316 s.s. bolts.

Raymond Egan
metalworking - Chicago, Illinois, USA
2003

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Well you can throw out chrome with that information. I would go to a heat treatable stainless steel. Even with the added information, it still is not enough. 10% nitric for how often, how long, what temperature, any pooling entrapment or other retention of the nitric, how many years does it have to last? Any exposure to chlorides?

Plain old 410SS might do. Other more exotics might be required. The recommended EN may work and it may not. Too many unknown variables. Is this low tech and low cost enough that you can try things to see if they will work in real use?

James Watts
- Navarre, Florida
2003