Welded 455 SS rusting

Phil:

It sounds like you might be getting heat tint on the tube interior. Do you purge the inside?

There is a detailed 52 page reference book on stainless welding you can get for free from the Nickel Institute. It is Nickel Development Institute publication No. 11007 titled "Guidelines for the welded fabrication of nickel-containing stainless steels for corrosion resistant services". There also is a newer 20 page book also, No 11026 on "Fabricating stainless steels for the water industry"

Go to:

On the top of the page is a box labeled "Nickel & Its Uses". Click on it. On the right side of the page is a column with a box labeled "Technical Literature. Click on it. Change the search box under Technical Literature Locator to be by Catalogue No., and put in 11007 or 11026. Then you can download the book. (You may have to register if this is the first time at the site).

Pittsburgh Pete

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Or it could also be something as simple as a porous weld. if you leave pinholes, and then passivate it, passivation solution gets trapped in the cavities.

bleedout is a common issue in plated items like cast iron where porosity is just the nature of the material

Hi Pete

I always get a kick out of telling our engineers here in the shipyard these alloys are "stainless" not "stainfree." I didn't check the NIDI article, but rather than a simple passivation, they might need a pickel to get rid of any free iron that might plate out on the cooler base material. There's a vapor above the liquid weld puddle that's iron rich and that iron will condense on the nearest cool surface. We had a case where our customer noticed rusty streaks paralelling the seam weld inside the refrigerator. I suggested they continue to clean the piece with a green scrub pad and a common tub and tile cleaner that contained citric acid.

J