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Reason of lite coloured patches after zinc plating

I have one clarification on light coloured patches. why these patches will come after plating. what is the major reason of this problem? how we arrest this problem? please give your valuable ideas.

VASANTH.A PRABU
Plating shop employee - Chennai, Tamilnadu, India
June 23, 2009

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June 23, 2009

Hi, Vasanth. Are the components tiny screws that are barrel plated, or are they large sheets or stampings? Is the zinc plating cyanide, acid, or alkaline non-cyanide? Is the chromate clear or yellow or black, and is it trivalent or hexavalent? Thanks.

Regards,

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

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June 26, 2009

Dear Mr.Ted Mooney,
we using alkaline zinc plating and trivalent blue chromating at vat plating.it is an automatic plant.we plated draw components not long sheets... I am waiting for your reply
Truly,

Vasanth.A Prabu
- Chennai, Tamilnadu, India

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July 1, 2009

Hi Vasanth

Did you use any sealant after passivation? Some time the sealant may cause this kind of problem. Fix the concentration of the sealant or Proper rinsing and drying will be the solution in that case.

Please correct if I am wrong

Regards,

Vijendran Sudeendran
- Chennai, India

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July 8, 2009

Mr. Vasanth,

First diagnose where from the problem occurs whether from plating bath or after passivation Check plating solutions conc. periodical maintenance, additives, control measures for plating bath if it is from plating. Suppose problem occur after passivation check pH of the chromate, conc, impurities level in the chromate bath.

P. Gurumoorthi
electroplating process chemicals - Chennai, Tamilnadu, India

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Dear Vasanth,

While using trivalent blue, make sure you are operating the passivation with correct parameters.

Do you refer coloured patches as iridescent colours on the job. Make sure you give the correct immersion time. Most the timing, the more you go away from blue and also depends on the position of the component. Try to passivate the component vertically and not horizontally. Try with a newly prepared passivation bath and use the best of the deionized water with conductivity < 10 microS.

Regards
Aurobind

S.V. Aurobind
plating process supplier - Bangalore, India
July 13, 2009