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Passivating stainless steel with helicoils installed?
February 17, 2015
Q. I have some parts that are 15-5 stainless steel and have Nitronic 60 helicoils in them. There needs to be some small rework on the parts, and they will need to be re-passivated. Should the helicoils be removed before passivation?
This would be painful to do, but I am concerned that the nitric acid would get in between the helicoil and the base material and stay there forever. This could potentially cause corrosion in the future or outgassing (The parts will be in vacuum).
spec: QQ-P-35, type II or type VIII
Engineer - Tukwila, Washington
February 19, 2015
If you use citric acid (QQ-P-35 is cancelled and the replacements both allow citric), then damage to the Nitronic from the acid would not be a concern. I'm not sure about outgassing, as long as everything is thoroughly rinsed and dried it shouldn't really be a problem I would think, and once the water is gone citric acid is a solid anyway (no gaseous form).
Of course the other way to do it is a citric acid based gel product. Spot passivate the reworked areas while keeping it away from the helicoils.
Stellar Solutions, Inc.