Electro-Brush Plating Cylinder Bores

[GrimesFrank]

I have been asked to write a repair specification to brush plate some cylinder bores with Nickel High Speed (NHS). I have read MIL-STD-865C and I know the pros and cons of using brush plating to refurbish, but I want to know is there any advice of what should go into this specification?

What situations would you never recommend using brush plating to re-establish bore diameter? I.E. fluid, temperatures, pressures, etc.

 

[MikeHalloran]

After you build the bore down, how do you make it round again? How do you keep the nickel from flaking off in that operation?

But first, what kind of cylinders?

Why are they built in such a way that repair by plating seems cheaper than replacement?



Mike Halloran
Pembroke Pines, FL, USA

 

[kenvlach]

If you have to ask...

The chemistry supplier should give you a procedure roughly:
Electroclean, Rinse (R), Acid activate, R, nickel strike plating (if required), R, brush plating, R & dry. Also, all concentrations & pH's, temperatures, filtration, current density.
Is it possible to heat the cylinder block to about 130^oF for a proper sulfamate nickel (low stress, high build)?

The proper equipment is dual anodes 180^o apart, adustable spring-loaded, on a rotating, traversing arm (back&forth the cylinder depth).* The anode covers should be slightly abrasive (like a mild ScotchBrite pad, but rather thinner) to eliminate roughness. Of course, need semi-cylindrical anodes with holes for electrolyte flow.
*Sifco has a basic one on p. 26 of catalog (but I think you still must improvise some slip connectors):

http://www.sifcoasc.com/download/PublicDownloads/Product Guide 2006 Rev. 2.pdf

Also, it's good to have a power supply with reversable polarity.

It costs a bit to do it right and to get someone trained. Unless you have a lot of this work, or small amounts but at frequent or irregular intervals, best to out-source to one of these companies or their referral:

http://www.brooktronics.com/

http://www.ldcbrushplate.com/homepage.htm

http://www.sifcoasc.com/main.asp?zone=1&detail=0

You can specify per the MIL and AMS specs: AMS 2439, 2441 or one of the new 2451/2, etc. specs.
Also, why not Cr plating? LDC (maybe the others, too) has a hard chrome via a less hazardous, trivalent-Cr plating process.

 

[GrimesFrank]

Forgot about this thread because the job died, it's now been resurrected;

MHalloran,
Its not an entire plate of the interior, just some scratch filling. Adhesion is a key test in this process, the MIL std only makes you put some 3M tape on it and pull we go beyond that. The cylinders are Ortman (Quincy) Series 3TH cylinders used in valve hydraulic actuators. Reapir isn't necessarily cheaper than repurchase, just faster with less redtape. (i.e. nuclear work environment)

kenvlach,
We already purchase this service (MetalAd Canada) however some questioning attitude contract engineer decided to put his two cents in saying we don't have specifications for these guys to do their work with. I have interviewed the vendor on their process, and am trying to formalize and get the key requirements I'm looking out for in these repairs.

Still looking for opinions, maybe I'll put a link in the Metallurgy forum.