What is causing the rolled edge of 316 stainless steel to rust. This is the only area of the tube showing signs of rust. Fishers appear along the bottom rolled edge of our 316 stainless steel tubes. Rust begins inside these very fine fishers when in contact with rain water. What is causing the SS to rust and how can we cure this problem.
Can your furnish photos, including close-ups of the corroded fissures?
Does rolling refer to the sheet stock prior to welding into tubular shape, or was some mechanical forming performed on the tubes?
Any specification on the tubing, e.g., ASTM A268, A511, A554...?
How was the tubing cut to length, and were the ends deburred and cleaned thereafter? Passivated?
Were ordinary steel tools used on the 316, or is there any contact with other metals?
My guess: The fissures suggest cold-worked tubing that is stress corrosion cracking (SCC). Possibly, A554 tubing (A268 & A511 require annealing) or some non-grade stuff. A true fix might require annealing + passivation, or may not even be possible if the surface is heavily cracked. If a large amount of material is involved, consider having a metallurgist or testing lab check whether it meets specifications. Very light rainfalls carry surface contaminants to the bottom where they concentrate as the water evaporates. There may also be some initial contamination from forming or cutting. The contaminants attack the heavily stressed, possibly microcracked material. If the material is installed architecturally, wash, apply an automotive chrome cleaner/polish and then wax.
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