Instruction Markings on Stainless Steel

[Metcorr]

One of our construction vendors on-site was observed using plastic tapes on stainless steel vessels as instruction markings. Our site-inspection group stopped this practice due to fear of stress corrosion cracking. Now, the vendor is using cryons for making instruction markings. Are cryons good alternate or also posses risk of scc to stainless steel. Will appreciate inputs from colleagues.

 

[weeeds]

We use special markers, certified for low chloride levels, for marking SS. These are readily available from your welding material suppliers.

 

[EdStainless]

Not only must they be certified as low in chlorides but the must also be fully removed as soon as possible. I have been crevice corrosion at the edges of paint marker lines.
We always used white chalk or black Sharpie.
Black Sharpie markers from Sanford are low in chlorides and other possible detrimental elements, but only black. Do not use colors.

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[TVP]

Some of the tidbits that I see here at Eng-Tips are quite fascinating...crevice corrosion at the edges of paint marker lines? It just goes to show that you really need to understand everything about your application...

 

[Metcorr]

Dear Edstainless,

Thanks for your post and valuable feedback. A crevice corrosion taking place at the edge of paint is really something that would worth noticing while inspecting vessels and tanks. Could you kindly elaborate if it is a common observation or just a couple of isolated cases in your experience.

 

[EdStainless]

I have only seen it twice. One time was on a tubesheet in brackish water service. The plates had been labeled with paint markers before the holes were drilled. The maker was not removed and the HX was fabed and put into service. When we opened it a few months latter and wiped off the tube sheet we could see rows of small pits along the paint lines. The alloy had marginal corrosion resistance in the water. It was either a 317 variant (LM?) or 904L, I don't recall.

The other case was on the exterior of a 304 unit near the coast. Ironically in this case the marking was related to the exterior coating that was going to be applied in order to protect it. In the couple of weeks before they go it coated they had pitting along some paint marks.

While paint markers usually go on very thin and stick well that is not always how it works. I suspect that these were related to locations where the paint went on thick and did not stick very well. After all you use special surface prep just to mark stuff.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm