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"Chemical passivation method for Inconel alloy"

March 22, 2010

There are many methods for the chemical passivation of stainless steel. But, I'm finding difficulty in finding chemical passivation method for Inconel 690. Can anybody help me regarding this?

Pradeep Samantaray
researcher - Chennai, INDIA

March 22, 2010

You can treat it the same way that you would stainless. If you have a slight amount of scale, then you should pickle it instead (which will also passivate it) in a solution containing nitric acid at around 40% by volume and hydrofluoric acid at around 3% by volume. The temperature could be ambient. The immersion time should be kept to a minimum which will depend on what you are trying to do. If it is clean non-scaled Inconel, 10 minutes is just fine.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri

March 25, 2010

Of course Inconel by itself doesn't need a treatment to be passive, as is generally true of non-ferrous alloys. However the parts may be susceptible to surface iron contamination, which can lead to surface rust. Concern over actual or potential iron contamination is what leads you to need a passivation treatment.

Since stainless steel passivation (nitric or citric acid based) is all about removing iron, the same procedures apply. Let us know if we can help.

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