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Ted Mooney, P.E. RET

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  for Metal Finishing 1989-2025
  

STANDARD NITRIC/FLUORIDRIC PICKLING/PASSIVATION OF AISI 430

The problem of the replacement of the standard pickling/passivation operations (HNO3/NaF) for type 430 SS is very complex, and it' s difficult to find out effective alternatives.
Our current traditional process is:
1. Degreasing in NaOH 10% sol, 55°C, 5 min
2. Acid pickling: HNO3, 30% sol, NaF 1%, room temperature, 15 min (see ASTM A380 -99, Table A1.1)
3. Passivation in 1% sol bicarbonate and phosphates, room temperature, 60 min
We are trying to replace this "old" treatment with a more ecological solution, keeping the original corrosion resistance.
Someone could suggest me something new (product and/or supplier) for the treatment of this type of SS?
In Italy I have had problem to find a supplier of "new" finishing products -based on H202 or citric acid , or something like this -(but effective also for the ferritic inox!).
..But I have another problem...
At the end of this process the passivated item undergoes a plastic deformation (drawing), that is damaging for the thin oxide layer.
It's possible to replace the AISI 430 with the more corrosion resistant AISI 430F,and to test more "friendly" galvanic treatments?


Thanks in advance

Best regards,

If your Stainless Steel parts are going for deformation process like drawing, then you should be doing the process after completion of drawing ; if permissible. If it's not possible then you can tell about your process sequence to suggest something else.

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