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Hi-phos hard nickel plating over epoxy?

March 29, 2010

I am trying to salvage and repair parts gone bad... We have a 4130 weldment that is blanchard ground to size, heat treated to 42-44 RC, followed by a Sisal buff and Hi-phos hard nickel. Problem seems to be a bad batch of gas in weld operation creating small worm holes that only revealed themselves in the finish grind operation. We can not repair and re-weld because parts are at final ground size and temper...to repair using Silver solder or equivalent braze process is time-consuming and costly.
My question is: Can we use a type of Epoxy to fill the small worm holes and then electroless nickel plate?
I know there are many epoxy metal composite products that perform very well, but has anyone ever plated them? This repair is not a structural one but only cosmetic.

Dan Rood
project management - Burbank, California, USA

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March 31, 2010

Not a good idea. Not only will EN not plate over those epoxy "plugs", it may discolor or even dissolve them instead. It will also prove almost impossible to bond properly to the actual EN plate perhaps leaving your part looking worst than before.
Your problem sounds like a good candidate for a fine argon welding job (spark welding would be much better), followed by a careful bench grinding of the spots. If desired, a brush plater can selectively plate nickel with excellent adhesion over the repaired areas to protect the exposed base metal and match color to the surrounding EN. Mold finishing or mold repair shops are a good starting point to look for help.

Guillermo Marrufo
Monterrey, NL, Mexico