Bright Annealing (BA) is an annealing heat treatment process in a protective gas environment (The dew point < -40C) or a vacuum furnace (< 10 exp -3 torr) in order to get a clean/bright surface as well as the desired microstructure & mechanical properties.

A protective gas environment;

For carbon steels & low alloy steels, BA is normally performed in a reducing environment (nitrogen or nitrogen/hydrogen) in order to avoid oxidation and decarburization on the metal surface and produce a bright & clean surface.

For austenitic alloys, a true BA must be conducted in a reducing environment that is dominantly hydrogen. This atmosphere will actually turn oxides on the surface of the tubing back into metals.
For alloys (such as ferritic stainless steels and titanium), that cannot be annealed in a reducing gas a BA is carried out in an inert argon atmosphere. These materials will have a small amount of surface oxidation even though they appear bright. They may require chemical cleaning to achieve their maximum corrosion resistance.

Mechanism: To prevent oxidation reaction in reducing gas or vacuum condition.

References;
http://www.rathmfg.com/Annealing.pdf
http://www.finishing.com/132/04.shtml
http://www.jindalstainless.com/cold-rolling.html

Hope this helps,
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