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Acid Zinc Plating Bath White Appearance

Q. I have an acid zinc plating bath. At the beginning when I made up the bath there was poor penetration around the holes, so our supplier recommended to add more Zinc Chloride and Potassium Chloride. However, even when the thickness increased not much the part turns white or matte finish.

We added more Brightener without improving the appearance of the part.

Do you have any idea about what could be the problem?

Sergio Samaniego
- Baja California
September 19, 2024

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A. Hi Sergio. "White appearance" could describe a number of different situations. Can you show us a part and/or a Hull Cell ⇦ huh? panel to better understand what you are trying to describe verbally?

At this point you've added more zinc chloride to your tank, and more potassium chloride, and more brightener, with no progress.

As a guess there might be something wrong with your brightener which is causing it to cloud the plating. Hull Cell testing allows you to add very small quantities and see what happens, and only scale up your whole tank after it works. Maybe you can carbon treat a beaker of solution and start over on a test panel.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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A. Hello!
You did not mention whether you are doing plating in rack or barrels ... anyway maintain zinc chloride between 70 to 80 gm/ltr, potassium chloride between 200 to 225 gm per ltr and boric acid between 30 to 35 gm per ltr and pH around 4.8 -- and also make sure the process of cleaning is good. Also pack activated carbon and zinc dust twice a week and do addition of additive and brightener as per TDS. You will never face any problem in acid zinc.

Sanjay Dhadwal
- Dubai, UAE
September 24, 2024

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