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Stainless steel laser etch problems

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Q. 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


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A. 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

Q. 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

A. 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



August 3, 2012

Q. We use the Citrisurf citric acid product and have good success for the most part. Some items do very well, and some do poorly. It must be the Chrome issue brought up by another answer. It is a bit of an art to passivate w/o removing the etch. We dipped them in a heated bath for awhile, but had some instruments that didn't fair well. We primarily use the Gel form and it works well. What I suspect is the use of highly alkaline cleaning solutions being used by hospitals causing the staining. There is very little actual Rust. I'm looking into just Acid etching now. Anyone need a really good fiber marking laser? What concentration of Nitric acid was being recommended? I wanted to try that on a few particular instruments that the Citrisurf seems to dislike.

Joe B Black
surgical instruments - Tucker, GA, United States


May 9, 2013

Q. Hello
somebody can recommend for the most effective procedure for passivation? what the best acid to use and what should be the percent of it?

Michael Rachilevsky
- Tel Aviv, Israel
  ^- Privately contact this inquirer -^

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