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  for Metal Finishing since 1989
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Pickle and passivating finish problem

2002

We pickle and passivate our 316L stainless steel. I think they use nitric and hydrofluoric acid.

We find two problems:

1. Any marks on the steel are enhanced, someone has even written on it and it is stained into the metal. Is it normal practice not to grind, etc stainless when passivating?

2. It comes back from the passivators with staining, typical brown run marks, if this is normal, what is a good method of removal? Are these expected astectic problems?

As you can imagine sales are not happy with the finish.

Neville Tubb
- UK

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2002

Hello Neville,

No. I would not expect parts to be ground when sent to be passivated, but I would expect them to be cleaned before they were etched, or pickled. Dye-chem or marker should be wiped off parts before they are processed. Stains are not indicative of a clean rinse system, BUT there are other possible circumstances which could cause this.

Bill Grayson
- Santa Cruz, California, USA