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

by Randy Taylor, Advanced Tooling Corporation.
July, 2006

Hard Chrome Over Electroless Nickel

Q. I have tried to improve the corrosive resistance of hard chrome plating by plating electroless nickel underneath. However, I have experienced peeling of the hard chrome layers. Please advise.

A. In general, nickel tends to passivate and must be activated. There are various methods to accomplish this. Be sure your nickel is properly cleaned and ready for chemical processing, including solvent cleaning and a hot soak electro cleaner.

Most common method for activation of nickel plating, 1.) 1 minute-forward / 30 secs - reverse / 2 minutes - forward, electrolytic activation in dilute, ambient, 5-15% HCL by volume with water (hydrochloric acid), or preferred, 2.) same fwd/rev/fwd process in 5%-15% H2SO4 by volume with water, (sulfuric acid), rinse thoroughly, keeping part(s) wet, then enter the chrome plating bath quickly with rectifier current on at 2-2.5 DC Volts, cathodize (forward current) for 1-2 minutes, then step voltage .2 volt/each 10 seconds until at full plating current. Make sure you are in good proximity to your anode source to encourage even current distribution and gassing.(if SCR ACC/ACV controls, set rectifier by Volt pot for both activation & plating).

Electroless nickel is tougher to chrome plate than electrolytic nickels, but it can be done. If your E-nickel is high-phos., or the e-nickel has been heat treated before chrome, you may have to hand polish with a fine scotch brite buff pad to burnish the nickel coating to enhance the surface conductivity.



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