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Hard Chrome plating and small holes

February 26, 2013

Q. I'm currently working on a design that has a metal part (latch) that is going to be exposed to the elements (outside location). Latch is made from O1 steel and it is under heavy load. Currently we are plating it with hard chrome for rust protection and wear resistance. The problem that we are facing is that the latch has several holes cut in it (1/8" diameter) which never get any hard chrome deposit in it and become the source or rust. I was wondering if there is any coating/plating that can be applied in a small hole?

Art Grig
- Tampa, Florida, USA

A. Hi Art. Hard chrome plating may well be appropriate for this latch . . . but when someone talks about rust protection when exposed to the elements, we have to question whether they have made the best selection as hard chrome plating doesn't offer the corrosion resistance of alternatives like electroless nickel.

If you are confident that hard chrome plating is the correct specification, some people do iron phosphatizing immediately after chrome plating, which would allow you to paint the holes.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 26, 2013

March 1, 2013

Q. Thank you for your thoughts. This application has a lot of force applied to a small area (a tooth of a latch). When latch is moved the "tooth" disengages and the weight is released. The area of the tooth that is engaged is roughly about 0.25"x0.06". So low friction and wear resistance was important in selecting the coating. Would nickel be hard enough for this application?

Art Grig
- Tampa, Florida, USA

A. Hi. Electroless nickel is quite hard and may be hard enough. Are the teeth hardened? If not, chrome plating may not be doing much good anyway. If so, a better approach might be salt bath nitriding / QPQ process.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 4, 2013

Mid Phos electroless nickel is the answer.

Vikram Dogra
Irusha India - Chandigarh, India
March 1, 2013

A. Hi,

Maybe the hydrogen gas. Turn the part's hole to left or right (horizontal) and plate the hole.

Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
March 4, 2013

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