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Ask the Expert Question-and-Answer Archive
(Hard Chrome Plating)

by Larry Zitko, ChromeTech, Inc.
August, 2002

Industry Standard for Re-Chroming Hydraulic Cylinder Rods

Q. Is there an industry standard for rechrome on hydraulic cylinder rods? Is there a maximum or minimum standard?

A. Hydraulic cylinders are usually hard chrome plated, in order to impart the desirable properties of the chromium to the steel rods or cylinders. Some of the desirable properties are: high hardness, low coefficient of friction, good wearability, good oil retention (due to the microcrack structure of the chromium deposit) and good corrosion resistance.

New hydraulic rods may have only a half a mil (0.0005") to one mil (0.001") of chrome thickness, but reworked rods typically have much thicker chromium. This occurs because old, worn rods are polished or ground extensively to remove pits, scratches and gouges, then electroplated chromium is used to restore the required dimensional tolerances. Often, the chromium layer on reconditioned (i.e. - replated) hydraulic cylinders will last longer than newly manufactured ones. I have often witnessed original OEM rods where the chromium had worn away in the regions that are wiped by the seals when the cylinder is repeatedly extended and retracted. The longer life for rechromed parts is probably due to the thicker chromium deposits, which can be 20 mils or more.

I am not aware of any one "industry standard" for chrome on rebuilt hydraulic cylinders. Rather, chromium is deposited to whatever thickness is needed to bring the part back to size. Sometimes, the plater is asked to plate to SAE Standard AMS-QQ-C-320, Class 2 (July 2000), which replaced the well-known U.S. Military Specification QQ-C-320B.




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