Metal finishing Q&As since 1989


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Pinhole defects on the buffed stainless steel strip surface

Dear Sir :
I have a question which has bothered me for quite some time and I have tried many different ways to solve it but in vain. The issue is that I always have found very tiny pinhole surface defects at ~100 micron in size and is probably due to melting of the stainless steel, since the application is for the consumer electronics so that it is not justifiable to use double V's in the melting/refining operations.
The material is 304BA strip at a gauge of 0.3 mm, the typical processing is stamping, deburring with plasma etching and followed by hand buffing. It is after the buffing operation, pinhole defects have occurred randomly which will cause rejections by the final customer and results in low yield rate, say, 75%.
I have tried to use some surface chemical treatment like inorganic costing before stamping and buffing operation, but the defects remain intact. I may have to use electroplating to cover the defects but it may be too costly and the pinholes may not be fully filled or covered.
Any suggestions or advices would be highly appreciated.

I-lin Cheng
surface treatment consultant - Kaohsiung, Taiwan, Rep. of China
April 15, 2010

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All polishing systems are basically negative material removal. They will only modify the surface profile. They will not create pin holes; therefore, the problem has to be in the raw material. If you can't improve the raw material then you will have to use a positive plating system to restore the surface profile.

AF Kenton
retired business owner - Hatboro, Pennsylvania
April 28, 2010