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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing 1989-2024
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Zinc plating with blue passivation is yellowish at holes
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Q. Hi everyone, need help. My company does zinc plating with blue trichrome passivation. We are encountering yellowish issue at hole areas.
Information on our process:
Degrease
Electroclean
Rinse
Acid pickling
Predip( NaOH)
Zinc bath (alkaline non-cyanide)
Rinse
Bright dip
Rinse
Blue passivation (tri Cr)
Rinse x4
Hot water (70 °C)
Blow dry
Oven dry (60 °C) 10 min
We have tried
1) change blue passivation solution
2) change bright dip solution
3) change rinse water
All specifications follow supplier spec
I'm suspecting the hot water & oven drying temperature may cause this issue?
Can anyone help me on the root cause & troubleshooting
- Perak malaysia
November 29, 2023
A. Hi Thivaharan
While we await someone with actual experience with this particular problem, I would suspect inadequate agitation in the chromate tank, or rinsing which is either not quick enough or not thorough enough.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. I think you can try after zinc plate, 5-6 seconds 1% by vol. nitric acid dip, follow up rinses then go to trivalent blue dip.
Popatbhai B. Patel
electroplating consultant - Roseville, Michigan
February 29, 2024
A. I think it might be water mark around hole. This is common problem in alkaline zinc plating. In my opinion you should try hot water dip at final stage and use hot air to dry.
Sanjay Dhadwal- Dubai
September 23, 2024
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