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Chrome plating defect at seam

December 10, 2008

We have a chrome plated tube with wall thickness of about 1 mm. In correspondence of the seam we have a sort of blistering, like burst bubbles, which are very perfect in shape (see photo).

The defect could be due to gas developing during machining? for example because of oil trapped inside lacks of fusion of the seam.

Thanks

Andrea Vecchi
technical lab - Modena, Italy

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December 21, 2008

Hi Andrea,
1 mm of chrome is a very high thickness for a chrome deposit, and what happens with the chromium deposit is hard to explain. It also can be in the substrate material, when operation by grinding and honing.

Remember also:
hydrogen in chrome operation
microcracks / macrocracks
parameters changing while chrome operation
trivalent chromium
catalyst
Grinding operation
lapping with oil operation
heat treatment before and after
Can have a effect what your picture is showing.

Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

Normally perfect round defects are indeed gas or air bubbles. If you have some sort of damages on the surface that can hold an air or gas bubble you get this kind of defects in your layer. The solution is in the mechanical pretreatment.

Erik van der Staaij
- Emmen, Netherlands
January 15, 2009