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topic 4001

Metal Parts are Nickel Plated but are still RUSTING


(1999)

One of the products my company offers is called safety clamps, for use with oilfield piping, and they are constantly exposed to the weather. These safety clamps are made from cast 8630 steel. Currently, we have specified a .0005 - .001" electroless nickel plated finish. However, we are running into severe rust/corrosion problems. I understand that going to a thicker plate,~.003", would probably mitigate some of the problems. We originally cast a stainless steel but the CA-6NM stainless that we used, while it resisted rust excellently, didn't give us adequate mechanical properties. When we switched to 17-4PH SS, we got the mechanicals but the parts rusted terribly.

I am a mechanical designer and have very little knowledge in this area. I know that one of you finishing experts could probably easily show me the error of my ways. Does anyone have any suggestions. (i.e. powder coating or ?)

Thanks for your time.

Glenn Hayes
- Ft. Worth, Texas


(1999)

Increasing your EN to 0.0015 minimum should take care of most of your problems.

Also shifting to a higher phosphorous content will help greatly. You probably are using a mid P of 5-7 %. Try increasing to a minimum of 9 with 10 or 11 being even better if you can get it for a reasonable cost including shipping.

Finally, try to find out what metal it is in contact with and what the environment is. If it is in contact with steel that is rusting, it will also rust. If it is in a marine atmosphere, hot and slightly acid it will also rust faster.

James Watts
- Navarre, Florida


(1999)

Hi Glenn ,

your problem might be as simple as using the correct specification ,

For the 8630 steel , the proper specification would call for , Woods Nickel Strike before electroless Nickel , The Electroless Nickel should have a minimum thickness of 1.5 thousands of an inch , but it MUST be Hi Phosphorous Nickel ( approx. 12 % Phosphorous ) , for some extra protection you could coat the Electroless Nickel with a minimum of 50 Millionths of an inch of Hard Chromium Deposit .

For the 17-4PH S/S the simple answer may be to electropolish the S/S , there by enriching the surface in Nickel & Chrome by selectively removing the Iron and at the same time "Passivating" the enriched Nickel / Chrome surface .

Best regards

John Tenison-Woods
John Tenison - Woods
- Victoria Australia



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