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Parts burning in alkaline zinc plating tank

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Parts came out from alkaline zinc tank burned at high current density areas, and the burn looks like white powder. The temp. in the tank is 85 deg F and the zinc metal concentration is 1.2 oz/gal and the caustic potash concentration is 20.0 oz/gal. We are using brightener and starter(refine rack). All parts are burning on the rack but the bottom and side parts are burning more. The current density we are plating at is 19 to 26 amps/sq. ft.

Popat Patel
plating shop
Roseville, Michigan

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Dear Mr PP,

You need to up the Metal conc. to 2 oz/gal and also ensure that the NaOH does not exceed what you currently have. Maintain a metal : OH ratio of 1:10 and you will regain control.

Khozema Vahanwala
Saify Ind

Bangalore, Karnataka, India

Thanks very much for the knowledgable and confident response, KV.

Regards,

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

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