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Surface texture after etching stainless steel

We are a small department in our company as a whole.
Recently we are having problem with the retaining surface texture after etching 304 stainless steel.
Especially with the BA, or mirror like texture which will be "fogged up" after etching and you can feel the roughness with your finger. Our current solution is adding ammonium chloride to the current mix of ferric chloride ⇦this on eBay or Amazon [affil links] and hydrochloric acid. But the improvement was very limited.

I was wondering if there are better solutions out there? Or can someone explain the what ammonium chloride is doing to the etching process?

Kevin Lin
etcher - Auckland, New Zealand
2007

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January 2, 2008

First of all, you want VERY MUCH to avoid putting the chlorides on stainless steel, if possible. Here you are adding 3 different chlorides, which is one of the worst things you can do to stainless steel.
If you MUST use ferric chloride to etch the steel you need to remove all of it from the surface after etching, neutralize with alkaline and then be sure to passivate afterward.
Etching the surface will ALWAYS change the surface appearance to a matte finish. You cannot etch the steel and keep a shiny surface.
The ammonium chloride is just buffering the acid.
Are there better materials out there to etch AND retain a mirror finish? I do not see how this can be possible.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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Hi, thank you for your replay.

I have been doing some research and it turns out you are right. it is not possible to retain the texture after etching.

So the ammonium chloride is used as a buffer solution? does it get consumed?
Also is there a method to determine the concentration my ferric chloride ? Just so that I can determine the life of the etchant. I was wondering if you could help me out?

Kevin Lin
- Auckland, New Zealand
January 7, 2008