Electroless Nickel Post Heat?

[rtgeorge]

When you have Electroless Nickel plating done commercially, they post-heat the part at 400° C for 1 hour, which greatly increases the hardness of the nickel plate (from around 40 Rockwell C to around 55).

Can the Caswell Electroless Nickel or Electroless Cobalt (Copy Krome) be post-heated to improve the hardness?

Thanks,

Robert

[CarWiz]

Yes, it does work but I've never gone that high. 400°F should be enough to harden and improve the adhesion to the base metal. Just make sure the finish is the way you like it before heating. It's harder to polish after as well.

Are you sure the temp is centigrade? Keep in mind that 400° C is about 752° F and well into the range that will temper or draw back most steels. It can cause many steels to shrink and crack the plating at temperatures that high too.

[rtgeorge]

Thanks for the response! What temperature did you use for post-heat?

The 400°C is from most of the commerical Electroless Nickel datasheets I've found:

"Hardness: 300 - 350 VHN as plated, 400 - 500 VHN (400°C, 1 hr)"

[CarWiz]

I use 400-450F. I would want to know what the base metal might be if they are using 400C. That could be for stainless steel or some specialized process. My information says 400F is enough. You sure don't want to bake many of the die-cast alloys at your temp or you'll end up with the part all over the inside of your oven.

[KCV6]

Reliefing a part at 400 deg F or around 200 Deg C for 2 to 3 hours is pretty much correct to prevent embrittlement and harden plating. Another tip is if you have agressively acid stripped the item and then plated and then Relief, the chances are the plating will blister. I strip (acid) then relief then mechanically clean then plate then Relief. Long Relief at lower temps is ok for a soft casting, as it is not high tensile to start with.

Cheers Mark

[rtgeorge]

Mark, thanks for the reply!

What acid are you using for the pre-clean?

[KCV6]

For steel items I use 10% hydroclauric (1/3 pool acid to 2 thirds tap water). Cheap and effective. Removes rust and zinc. Most of the items I do are off of old cars and require at least an hour soak, which will definately load the part with hydrogen.

There use to be an aluminium cleaner called CT-13, was a thick liquid and pink in colour and available at most Truck parts stores. This stuff mixed in water use to work great for removing zinc and rust as it contained other detergents and additives which seemed to reduce the amount of grey/black smut that forms on acid dipped parts.

Hope this helps

cheers Mark