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Alternative zinc finishes for sheet metal





October 21, 2010

Hi ,

We are facing crevice corrosion between lap joints( one is 4 mm and other is 0,7 mm) by fasteners.
Primary corrosion happened on less thickness(0,7 mm) sheetmetal (customer part) and transferred to our part (4 mm) as secondary. Because of size ,Customer they could not able to increase their thickness and profile or Zinc plating thickness

Our customer saying that to increase the zinc thickness from 13 microns to 30 microns which helps to less thickness sheetmetal from corrosion.

If we use regular electroplating(dipping) process, There is possibilities of Hydrogen Embrittlement problem because After assembled the parts going to paint shop( 250 degrees).

My understanding is Mechanical plating can be used to achieve 30 microns zinc without Hydrogen Embrittlement, But it is cost effective and there is limitation in size (200 mm)

Is there any barrel to plate the part which one having length 270 mm and width 100 mm?( profiled)?

Do you have any suggestion ? Whether we can achieve 30 microns by normal dipping process or mechanical plating ?

Thanks Arunkumar

Arunkumar Rengachari
Resident Engineer - Koeln, NRW, Germany



November 24, 2010

Hello Mr Arun kumar,

There are alternative vibratory equipments instead of tumble type to coat larger size fasteners than 200 mm with mechanical zinc. However I suggest you do for a duplex coat of mechanical zinc with a zinc flake based topcoat for a workable solution. You may get the corrosion resistance you want by this process at a much lesser coating thickness.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind
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Bengaluru, Karnataka, India
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