Letter 4878

Passivation, Cold ? 

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Readers, I am a manufacturing engineer. I have recently been assigned a task to locate a method to passivate areas of weld on a test system cabinet. The material is 304L Stainless Steel. Our customer wishes the area of weld to be passivated.

The cabinent is too large to send out to be tanked in a passivation bath. Hence, I am seeking an alternative to comply with our customer requirements. A method we might be able to perform safely in-house would be prefered. A co-worker has mentioned a method called "cold passivation". I am not familiar with this method. Any helpful information forwarded would be appreciated. Thank you, Mark G. Mfg. Eng.

Mark Gingerella
- Brea, CA USA

I would write a process specification (times temperatures, materials, chemicals (with an appropriate short section on theory of corrosion relating to this problem, with references): polish the weld after all other operations (no steel wool or iron scrapers) with half whiting and 00 pumice on a soft rag with a little ammonia. wipe with a wet cloth then dry with a soft cloth such as flannel. You may also want to test the weld area with ferroxyl indicator to have a measure of the corrosion potential of the weld and other areas of the cabinet. If the test is positive for iron, it may be necessary to remove embedded iron with other techniques (acid, dichromate etc.)

Tom Pullizzi Platronica.com Falls Township, PA

Mark:

This is a very common request that we receive. We have several CitriSurf citric acid based products that work very well for this application, depending on the condition of the weld and the desired results. We can obtain excellent corrosion resistance in the weld area after passivation.

We would be happy to run tests for you, or to send you samples. We have good products that are in the gel form so that it can be sprayed or painted onto the surface. Let us know if we can help. Lee

Lee Kremer Stellar Solutions, Inc. Algonquin, IL, USA

Hi Mark , Your task seems the perfect oportunity for Brush Electropolishing , which , if done correctly , will give all the benefits of passivation by other means , and a good looking finish as a bonus . I suggest you contact Brooktronics Inc in Valencia California , they will come & do the job on site . regards

John Tenison - Woods
- Victoria Australia

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