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Stainless steel laser etch problems

I am a designer of Medical devices/instruments. The primary material in use is stainless steel, 17-4 PH heat-treated to H-900 condition.

After laser etching part numbers, we have the instruments passivated for corrosion resistance.

After passivation, our laser etching is all but non-existent. If we laser etch before passivation, the area of laser etch corrodes after autoclaving.

Any suggestions on how to finish for corrosion or laser etching with reference to technical documents would be appreciated

Anthony Rubino
- San Diego, California

Anthony:

This is a typical problem. The laser etched area is the weakest area on the parts and must be passivated to prevent rusting in the etched area. However, it can be very difficult to get the etched area passive without removing ALL of the darkened color used for identification.

We have had great success with our citric acid formulations in producing excellent corrosion resistance in the laser etched area without removing the color. Many surgical instrument companies have gone to this system because the amount of problems and rusting are significantly reduced compared to nitric acid passivation.

Let us know if we can help you.

Regards,

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

May 16, 2008

I would like to know if Anthony has found a solution to the problem as I have the same problem.

Bill Buttermore
- Cincinnati, Ohio

March 5, 2009

Passivation of stainless steel that has been laser etched must be done with a different solution of Nitric acid. If you have found this problem to be intermittent, it is due to the variation of the chromium content in the SS. For the laser etch to hold the chrome content must be above 16%. 17-4 stainless rides right on this line. Any washed out laser etch issues will have lower chrome then this. If you are experiencing these problems, you are probably using a nitric 2 bath. The solution is to use a nitric 1 bath which is a lesser concentration of acid or to use citric acid.

Nathan Meyer
- Avilla, Indiana

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