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Electroless Nickel / Hard Chrome Plating Hardness

We are looking to coat the inside of an Aluminum cylinder with either EN [electroless nickel], Hard Chrome Plating, or Hard coat anodizing. We have tested both EN And Hard coat anodizing and although they work we would like to increase the hardness of the EN finish. We understand that with EN that a greater hardness can be achieved by post baking the parts at temperatures exceeding 500 °F. However we are concerned about do this because the material properties book indicates that Tensile and Yield strength of the material starts to decrease after you reach 300 °F. Any suggestions?

Frank Buchholz
shock absorbers - Atlanta, Georgia, USA
2006

How hard is the electroless nickel you have been using? There are electroless nickel deposits that are around 60Rc as plated.

Todd Osmolski
- Charlotte, North Carolina, USA

There is an English company in Auburn AL, near you, that occludes silicon carbide dust in a sulfamate nickel deposit on the inside of aluminum cylinder bores.

After zincate and a nickel strike you can occlude diamond dust or silicon carbide in the electroplated sulfamate nickel deposit by keeping the media suspended in the solution by agitation. That is a very HARD surface.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

EN or Hard chrome would be your best bet, they do have En solutions out there with a as plated hardness of 62Rc (without baking). I would look at what's the most economical for your application, and what level of hardness you really need to meet your standard.

JEFF W LENTZ
Plating Co. - Lancaster, Pennsylvania

Talk to a vendor about a low phosphorous EN. It is harder out of the bath and has a heat treat cycle that may be a little bit lower.
Boron EN is great, but it costs quite a bit more.

James Watts
- Navarre, Florida

There are low phosphotous EN formulations that produce a harder as plated deposit (claimed to go up to 60Rc). Maybe they meet your requirements.

Guillermo Marrufo
Monterrey, NL, Mexico

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