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  for Metal Finishing since 1989
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Passivation and Etching

I am writing from a stainless steel strip supplier and I am wondering what effect passivation may have on the etching of stainless steel strip. I have read the articles that have been put down here and I have heard that tooling and machining can change the stainless so that it may not passivate or it will passivate the parts differently but I need to know that if the stainless strip is passivated before we send it out in strips of thickness down to 50 microns will the machining that this has gone through effect the passivation and how will the passivation affect the etching (Photo Chemical Machining) of this product.

Pete Anniss
Metals Supplier - Kingsbridge, Devon, UK
2003

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First of two simultaneous responses -- 2003

Is it chemical etching, laser etching or mechanical? Assuming that it is chemical etching, there will be some effect of passivation on the speed of etching, possibly, but not likely. It depends on the chemistry used. For laser etching it will make no difference.

Machining of the strip can definitely affect the way it passivates, but proper passivation will always render a good passive surface. There is a lot of material on the affect of machining on the surface properties and Passivation. The temperature that the surface reaches during machining can dramatically affect how the surface passivates, for instance. Proper machining produces surfaces that passivate VERY well.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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Second of two simultaneous responses --

Photochemical machining will proceed regardless of passivation. It is so aggressive that the passive layer is readily dissolved. Oils, grease and other stuff like paint will indeed act as barriers, but people doing that type of work always clean the surface to remove all that.

Guillermo Marrufo
Monterrey, NL, Mexico
2003