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Aluminum tubing corrosion in stainless flange

September 27, 2010

My application is in a nuclear plant on the N-16 monitoring system. We have 6061-T6 aluminum tubing, 3/8-in OD, attached to a 316 stainless flange with a stainless male NPT Swagelok fitting. We are experiencing what appears to be galvanic corrosion right above the ferrule of the fitting. The tubing line is subjected to stagnant flows the majority of the time. If we used an aluminum fitting, would this just transfer our corrosion problem to a different area...perhaps the threads of the fitting, or is there a better solution. Using stainless tubing is not an option.

Rob Howard
Design Engineer - Idaho Falls, Idaho, USA

October 9, 2010

A few more details are necessary, but the starting point is that, yes, galvanic corrosion is a serious issue. I assume the aluminum is finished: hardcoated, perhaps, to give it wear resistance? An anodized finish will give it some electrical insulation, as well: the thicker, the better.

Any number of conditions can allow for electrical conductivity in this system, which allows for galvanic corrosion. Isolating them all would be like Hercules facing the Hydra! Therefore, your goal is to insure that all components are grounded in addition to being insulated.

Mike Burnson
- Chicago, Illinois, USA

October 11, 2010

Just a question: Would it be possible to use an ultra thin film corrosion preventative compound between the 6061 and the stainless steel. The CPC would have to be a non-harding "self-healing" cpc and have a high dialectric.

Larry Clark
- Brunswick, Georgia

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