Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)
by Larry Zitko, ChromeTech, Inc.
Triple Chrome Plating
Q. I heard someone use the term "triple chrome plated". They explained that
the steel part is dipped three separate times in a solution before being
polished. They claim that the chrome comes out thicker. Is this possible?
A. Due to the low efficiency, slow plating speed and tendency for chromium to
produce rough deposits with heavy buildups, platers will often plate a part
requiring a thick chromium coating over more than one plating cycle. It is
fairly common to grind or polish the chrome after the first layer, then
plate "chrome-on-chrome" as needed to get the desired dimensions. A special
activation technique is needed to accomplish a satisfactory bond between the
two chromium layers.
The polishing step after the first layer will result in smoother subsequent
deposits. It can also improve the corrosion resistance of the final product
significantly, because it creates a smeared boundary between the microcracks
in the first and second layers of chromium. Generally, there is no need to
polish between any subsequent layers.
Most parts are plated with chromium using a single plating cycle. This may
not be possible if the required chromium thickness is too great, or if the
plater cannot accurately estimate the plating rate of deposition and plating
time. Platers will often pull a part from the chrome tank, measure it
quickly, then immediately return it to the tank and resume plating if it
needs more thickness. This process may be performed more than once. If the
part is not polished in between, the part may have a rougher deposit, even
it receives the desired final thickness of chromium. Also, this procedure
may result in a weak bond with the potential for peeled chrome.