Stainless corrosion. Passivate or no?
Stainless corrosion. Passivate or no?
(OP)
I am a mechanical Engineer and Im trying to get a better understanding as to what happens to stainless tubes when you use an abrasive cutoff + deburr. If you dont flash pickle, is the resulting corrosion caused by iron/contamination deposits, or is it thermal oxides, preventing air passivation from taking place. FYI the cut-off wheels are bonded aluminum oxide, the deburr is stainless wire brush. I dont have a scanning electron microscope nearby so I am unable to verify what is happening, if anything, to the parent material.





RE: Stainless corrosion. Passivate or no?
Are you sure the discoloration at the end of cut is corrosion? For "iron" contamination you need somehow the presence of iron contaminants in the vicinity of you stainless steel tubes, which you don't have apparently.
I assume also that the stainless steel tubes you mentioned have more than say 13% Chromium, which is enough for the restoration of protective layer of chromium oxide. There are other corrosion activities to affect the stainless steel, but those are related to the "corrosive" environment and process fluids and are function of time (much longer than that required to cut the tube). If the appearance is the issue, pickling is your answer, otherwise try slowing down the cutting disc and/or ignore the discoloration.
cheers,
gr2vessels
RE: Stainless corrosion. Passivate or no?
RE: Stainless corrosion. Passivate or no?
RE: Stainless corrosion. Passivate or no?
Cold cut with a good coolant will reduce your issues, but after brush deburr a flash pickle or at least a good passivation is a good idea. Maybe a citric acid passivation would be enough?
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Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
www.plymouth.com
RE: Stainless corrosion. Passivate or no?
RE: Stainless corrosion. Passivate or no?
RE: Stainless corrosion. Passivate or no?
There are other problems besides Fe that can lead to rust or blushing on SS.
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Plymouth Tube
RE: Stainless corrosion. Passivate or no?
RE: Stainless corrosion. Passivate or no?
HEAT TINTS ON STAINLESS STEELS CAN CAUSE CORROSION PROBLEMS
The dark heat tint formed alongside welds during welding of stainless steel (SS) the heat-affected zone (HAZ) is a thicker chromium oxide scale with a mixture of iron, nickel, and other oxides. This thin layer is lower in chromium, the primary constituent that gives SS its good corrosion resistance. Corrosion that would not occur elsewhere can initiate in the HAZ unless the heat tint scale and the thin chromium-depleted layer just beneath are removed. Removal by rotating fiber brush, pickling, or electropolishing readily restores this area to base-metal resistance.
http://
S.
http://www.corrosionist.com
RE: Stainless corrosion. Passivate or no?
Smear it on and use DI water in a mister to keep it moist.
I love to shame fabricators.
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Plymouth Tube