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Passivation of Stainless Coil

 

I am a metallurgist at a steel mill. We produce flat rolled steel in coil form. We have been producing 409 stainless steel for a number of years with good success, however our steel is not passivated. Traditionally, this is done to the coil on an anneal-pickle line, but due to our facility size, and because it would require us to build a new line this is not an option. Several companies have worked with us to develop a passivation line that essentially would be a modified pickle line. However, due to our processing we have a surface layer of titanium carbide present on the strip, and it hinders passivation. Confirmed by Auger analysis. This layer is quite resilient, and difficult to remove by chemical means. What has been experimentally confirmed is that this surface layer is readily removed by electropolishing. However, electropolishing doesn't appear to be used on stainless strip (30" to 55" wide). Since electrogalvanizing is the opposite of electropolishing this seems like a logical approach. Run an electrogalv line with reverse polarity.

Finally my questions. Does anyone currently use a process of this type on stainless coil? It doesn't matter what grade as long as it performs the function. If no one is currently doing this, who might I contact for information on setting up a line of this type?

Jeremy Cotton
- Crawfordsville, Indiana

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

Yes, electro-polishing is possible in stainless steel coils and strips. This process is now being used in South-east Asia and is successful.

Jasbir Bindra
- New Delhi, India
July 23, 2009