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Cast Iron Rust preventative coating or finish

I am looking for a rust preventative finish for machined cast iron parts. The finish that has been used in the past it electroless nickel plating. The finish must not outgas or give any vapors off due to the items being used in an optical environment. The nickel plating that was used was not consistent enough, too much build up in places. So I am looking for a similar process that can give a very good rust resistance and even finish on complex parts.

Thanks,

Todd Davis
Lawrencville, New Jersey
2001

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If your electroless nickel plating was not consistent or even, there was something wrong in the way the plating bath was running. E'less plating deposits the same thickness on all wetted areas of the part, apart from some other problems like depletion of the local solution, or insufficient activation of the base metal.

  
Tom Pullizzi
Falls Township, Pennsylvania
2001

Cast iron is a nasty thing to plate because of cold shuts (shots) and general porosity. Excessive activation can open up holes that are so heavy in oxides that it will not activate and they are large enough that they will not plate over and seal it.

Vacuum impregnation is one way around the problem.

Copper strike and heavy copper plate followed by buffing has been used in some cases. You may have to switch to a higher quality casting.

James Watts
- Navarre, Florida
2001