Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Larry Zitko, ChromeTech, Inc.
1. I have noticed that some portions of hard chrome plated surfaces are
peeled off during the final grinding, What is cause of it?
2. Can you give me suggestions on how to achieve quality finish of hard
When chromium fails in post-plate grinding, this indicates an adhesion
problem. You did not mention the type of base metal, whether you are plating
"chrome-on-chrome" or whether you can see the base metal in the areas where
the chromium deposit has peeled. I will assume that you are plating on steel
substrates, and that the peeled areas go all the way down to the steel base
This kind of peeling indicates poor adhesion between the chromium and base
metal. The post-plate grinding is a pretty good test for adhesion, so often
times a bond problem will present itself in the grinding operation.
Adhesion problems for chrome-on-steel seem to center around two areas:
1) Inadequate cleaning
2) Improper activation
You did not describe your cleaning or etching procedures, or the type or
size of your parts, so I can't make suggestions that are specific to your
parts. However, I have the following general comments:
Make sure that the plated regions of your parts are free of all oils, soils,
films and foreign materials that would interfere with the chromium bonding.
You may have to improve your cleaning operations. Perform the "Water Break
Free" test after cleaning. If you are not already familiar with this common
test, here is a brief summary:
Spray the cleaned and rinsed part with water. Observe the motion of the
water as it runs down the plated area of the part. If the water runs down in
an uninterrupted sheeting action, it is free of "water breaks", and
considered clean enough for hard chrome plating. If you see any areas where
the water diverts or gathers, this indicates areas which are not clean
enough. If your parts are large and the plating cycle times are long, a good
cleaning method is to scrub the parts with wetted pumice on an abrasive pad
(3M Scotch-Brite), then rinse thoroughly.
The degree of reverse etch activation is critically important, because it
will also affect bond strength. The degree of reverse etch is determined by
both the current and duration during the reverse etch activation procedure.
Defining the right etch is bath-specific, part-specific, alloy-specific,
anode-specific and is also affected by any case hardening procedures that
may have been performed on your parts prior to plating. Some parts cannot be
reverse etch activated, and must be immersion etched or electroetched in
other acids. Make sure that the parts are properly etched.