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Tarnishing of zinc plated parts after baking for hydrogen de-embrittlement

We manufacture Spring steel components mainly washers which are hardened and tempered to about 44 to 46 HRC. These need to be Zinc plated up to 10 microns thickness and yellow passivated. Our problems are as follows.

1) The surface appearance of the plated parts deteriorates after baking at 180 °C. It becomes dull. We need to hold the washers for at least 3 hours at this temperature to minimize the cracking.

2) What is the way to maintain the shining and colour of the plating during the baking ?

Sandeep Desai
mfgr of steel washers - Thane, Maharashtra, India
October 12, 2010

This comment is based on the way that you said it, IE: You are plating, chromating and then baking. That is guaranteed to give you a matte finish and the chromate will be nearly useless. Plate then bake then chromate. You might have to do a quick very dilute acid dip (probably nitric) before the chromate step.

James Watts
- Navarre, Florida
October 13, 2010

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Dear Sandeep Desai & Mr. James Watt,

Please follow the following process for heat treated spring steel Zinc plated parts.

Cleaning, Pickling, Zinc Plating for 15 min, Hydrogen relieve for 3 hrs, Bright Dip 10 ml/lt HCl or HNO3, Zinc Plating for the thickness required, Passivation.

I ensure there will be no Plating peel off and cracking of spring steel parts.

Thanks & Regards,

Parashar s R

Sanjeev Raman Parashar
- PUNE, Maharashtra, India
January 2, 2011

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It works.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

March 19, 2011