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Performance of decorative chrome plating at high temperature

we are doing nickel plus chrome plating, problem arises when chrome plated article comes in high temperature (approx 200 C) it gets yellowish color in some areas. Concentration of chromic acid is 200-225 g/L, sulphate ions are 2 g/L Current density is 23-30 A/dm2. Sometimes this comes too much which is not affordable. Can anyone help me to solve this problem

Muhammad Umair khan
PLATING SHOP EMPLOYEE - Lahore, Pakistan
January 3, 2011

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With no more information than what is given, the highest probability is that the chrome is not thick enough in some areas/parts. Oxidized nickel is slightly yellowish and that is probably what you are seeing.I do not know if it will help, but use a cotton applicator (long Q-tips ⇦ on eBay or Amazon [affil link] ) and swab a yellow area with hydrochloric acid. If there is chrome there, you should get a green color and the yellow should disappear. For reference swab a bright chrome area with a new Q-tips ⇦ on eBay or Amazon [affil link] and see how much color you get and what the remaining surface looks like.
Now do the same thing with nitric acid. Nitric will dissolve nickel, but not chrome. If you get a green color here, you are looking at nickel.

James Watts
- Navarre, Florida
January 3, 2011

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January , 2011

Hi, Muhammad. Letter 26051 claims that a way to get away from discoloration of nickel-chrome plating at high temperature (motorcycle exhaust temperature) is to plate the nickel without any brighteners and hand buff it before the chrome plating.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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