Difference between depassivation and deoxidation

A. Personally, I've never had occasion to use the phrase 'depassivation' in a career of several decades in metal finishing, Mobius. The point being that, although words should have precise meanings, trying to imbue a word which is not found in a dictionary with a precise meaning which is not dependent upon application and circumstance and context, isn't working. Try to explain the context in which this argument arises and someone may be able to throw light on the situation and help you solve the problem. Good luck.

A. Mobius

The two terms can probably mean the same in certain situations.

Depassivate, to me, means to make the surface reactive. There was an earlier post where a SST part was passivated, then 'depassivated' in areas to receive a carbon nitriding process. My take on it was that having a reactive surface improved adhesion.

Deoxidizing is to remove an oxide layer, which in turn makes the surface reactive.

In plating zinc where a post-plate hydrogen embrittlement relief bake is performed, the zinc must be reactivated (it becomes passive from baking) for subsequent chromating.

Hope this helps.

A. Lal,
Seeing that high speed steel is not a class of stainless steel, I would suspect that no passivation has occurred and therefore no "depassivation" is needed.

Speaking as a chemist, I think the preferred term would be "activation" as the opposite of passive is active. "Deoxidizing" in terms of removing metal oxides from the surface also sounds acceptable. In most cases this will be the same thing as the majority of passive layers are composed of metal oxides, and removing it exposes an active surface.