Electroless nickel plating of model airplane pistons
I'm fly model aircraft of the radio control variety. Most of the engines use ABC,ABN or AAN technology. Eventually, even these wear out and compression is lost with resultant loss of power.
A Russian engine uses a hard anodized cylinder along with a nickel plated piston. This gives you a hard/soft combination that is much better wearing than traditional methods.
It occurs to me that if we could replate nickel cylinders, we could restore the compression to near new. Conventional plating gives an uneven deposit with the need to rehone or lap to dimension. A solution to this seems to be electroless nickel plating. This is supposed to give you a very even, thin coating without the complexity of electroplating. The thin even coating would eliminate the difficult honing step.
Is electroless any good? Will it replate nickel? Will it replate chrome? Will it really stick under the heat and pressures encountered in a model engine? These engines use high silicon aluminum pistons.
Also, I need to know what readily available material can be used for masking when plating or hard anodizing.Andy Woitowicz
- Timmins, Ontario, CANADA
I would like to find out the answers to this letter (9204). I want to nickel plate an iron piston to improve the fit in the cylinder to recover lost compression.David Crocker
- Ontario, Canada
October 8, 2009
To answer Andy's questions first: Yes, electroless nickel plating is certainly done and doable. It does give an even, thin coating. It will replate nickel, but the chrome must be stripped off before electroless nickel plating. I do see a technical issue, though: Although electroless nickel itself is heat resistant and should have no problem with the pressure, plating on aluminum (especially high silicon aluminum) is a special case because it involves a zincating step which is not as robust as most plating processes. There is a chance it will work, but I am not familiar with electroless nickel being used on pistons (although electroplating of pistons with nickel laced with silicon carbide particles is common -- see letter 1671 for a good discussion of that).
You might look in the library for Mallory & Hajdu's "Electroless Plating" to get a good understanding of the process. It's a bit hard to explain because the electroless nickel step per se is only one of several required steps, including cleaning, etching, de-smutting, zincating, and possibly a tarnish-inhibiting post dip.
Electroless nickel plating is usually considered an industrial science rather than an avocation for a hobbyist. So an alternate plan might be to find an electroless nickel plating shop (they're common).
But if you want to do it yourself, you'll need to find a supplier who will ship the solutions to you. Not all of them will due to their product stewardship policies and fear of liability (you probably are not certified to work with hazardous materials, so they may be worried about their responsibilities if something goes wrong).
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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