Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Randy Taylor, Advanced Tooling Corporation
Hard Chrome and Pitting
Q. I am wanting to re-do the hard chrome on Land Rover swivel balls, the balls have some pitting from rust. Will the hard chrome fill these holes without showing blemishes? And, must one grind after hard chroming?
A. The answer to your question is "negative", chrome will not fill pits or voids. Some additional work must be done to remove the problem before plating.
Chrome tends to "mirror" the surface being plated so imperfections such as pits, scratches, even fingerprints may show up in the chrome coating without the proper surface preparation.
Base metal imperfections such as pits, scratches and voids should be polished out, or opened up and blended with the surrounding metal in order to provide a suitable smooth surface for the plated coating. Hard chrome shops typically use grit blasting or glass beading as a final preparation step over polishing and pit removal.
Grinding after "hard chrome" is pretty common, limited only by the size and configuration of the surface being ground. Grinding before plating may help eliminate or at least reduce surface imperfections.
Decorative finishers sometimes use pre-coatings of acid copper and bright nickel to fill small imperfections before chrome is applied.