Metal finishing Q&As since 1989
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White haze and rainbow affect on chrome plated parts
Our company is having several parts bright chrome plated by a company and the results were less than ideal. The samples displayed a slight white haze, or else a rainbow affect when tilted and viewed in the right light. The supplier said the tool required additional polishing, but I believe this is a process issue rather than a tool issue.
Can someone provide some specific feedback as to what the possible cause might be, as well as possible solutions that we can test, and move forward with to correct this in production? We're already behind schedule and any help would be greatly appreciated.
Buyer - Apex, North Carolina, USA
November 11, 2010
November 16, 2010
JOHN,
MILKY DEPOSIT PROBLEM, TOO MANY REASONS ,CHECK THE FOLLOWING LIST.
1) CHROMIC ACID/sulphate RATIO -------INCREASE CONCENTRATION
2) HIGH CHLORIDE CONCENTRATION IN CHROME TANK--REMOVE CHLORIDE
3) IRON CONTAMINATION-----DILUTE THE BATH
4) EXCESSIVE TRIVALENT CHROME- CLEAN ANODES AND REOXIDIZE ANODES
5) LOW TEMPERATURE--INCREASE TEMPERATURE
6) CURRENT DENSITY TOO HIGH --ADJUST ANODE-TO-CATHODE RATIO
7) INTERMITTENT CURRENT LOW---CHECK ELECTRICAL CONTACTS
8) POOR NICKEL SURFACE---CARBON TREAT NICKEL TO REMOVE ORGANIC CONTAMINATION
Popatbhai B. Patel
electroplating consultant - Roseville, Michigan
November 23, 2010
Well, well, it could be a lot of things. Let's divide them into three groups:
1. White wash
2. Wrong sulphate concentration.
3. Too low anode area or bad contact of the anodes.
You mentioned that you have not only white haze but rainbow as well. Rainbow is a sign of too low sulfuric acid.
If the haze is irregular - it is probably white wash. BUT if the haze is in the high current density area, it could be too high sulfuric acid.
The first and most simple remedy of white wash is changing the rinses between the nickel and the chromium.
Also reduce the time in the rinses to minimum.
Do not let parts to dip in the chromium solution with no current.
Sometimes a short dip in the chromium drag out prior to entering the chromium plating solution, is beneficial.
Sara Michaeli
Tel-Aviv-Yafo, Israel
Blackening copper is not an option because you convert the copper to be isolated
You can silver plate the contact improving the electrical conductivity and if the silver get black still conduct,
and if you want to be more sophisticated you can plate silver with nanodiamonds which improve the anti-scratch behavior and the heat transfer also
Bnei Berak, Israel
December 25, 2010
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