Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Larry Zitko, ChromeTech, Inc.
Chromium Plating Efficiency
Q. I'm a student doing some general research on chrome electroplating. My
question is, on average, what percentage of the chrome used in the plating
process actually gets plated on the substrate? What percentage of the chrome
is left over for waste water or sludge on average?
A. The numbers are difficult to estimate due to the many variations in the
designs of the hard chrome plating equipment and the techniques employed by
the plating operators. Let me explain.
Some facilities still send chromium-bearing rinse water (from rinse tanks)
and chromium-bearing fluid from air pollution control devices to their waste
treatment system. In this situation, the amount of chromium waste can be
hundreds or thousands of pounds per year. Modern hard chrome facilities are
often designed with waste minimization and pollution prevention goals in
mind. All rinse water can be reclaimed to the plating tanks, as well as all
wash down fluid from the air scrubbers, if they are dedicated. In this case,
the only chromium existing the system may be the controlled air emission
exiting the stack, as low as 5 lb. / year or less as . Hard chrome plating
lends itself well to reclaiming these fluids because the bath is quite
forgiving of contaminants and its high operating temperature (115-150 deg.
F.) evaporates a lot of water vapor.
The rate at which chromium is dragged out of the plating tank and into the
rinse tank can vary significantly (1 gal to 10 gal or more per 1,000 ft2
plated) depending upon part shapes, racking design and operator techniques
Modern composite meshpad mist eliminators used for extracting entrained
chromium from exhaust air streams are highly efficient, often 99.8% eff. or