Summary for galvanic corrosion test Discussion
Galvanic corrosion test for titanium anodize AMS 2487 is questioned by Mike Palatas, who says the spec’s B117 one-week fastened-panel test seems vague and unfair because the bare 1100 aluminum plate will corrode, especially where salt solution can sit between the plates. He notes inconsistent results from multiple labs and asks what counts as pass or fail. The only reply in the thread is a cautious guess from an unnamed answerer: the edges may need to be taped or masked, because the corrosion of interest might be on the outside surfaces rather than between the panels. The answerer also agrees that a specification should clearly define pass/fail criteria for any required test. No definitive interpretation of AMS 2487 is given in the thread, so the discussion mainly highlights ambiguity in the test method and the need for clearer acceptance criteria.
Q. We are an aerospace metal finisher who anodizes titanium per the AMS 2487 specification. That spec requires, among a lot of others, a periodic test for ‘galvanic corrosion’. The method specified is to tightly fasten a titanium anodized 1″ x 6″ flat plate to a similarly sized, bare, 1100 alloy aluminum plate using nylon bolts through (2) holes in the opposite ends. You expose that assembly to salt spray ASTM B117 for one week and then ‘check for evidence of galvanic corrosion’.
I can find no spec governing that test and nothing that might give a hint of what a pass or fail would look like. Obviously, the bare aluminum is going to corrode — especially at the junction of the two plates, because unlike in a standard salt spray test where a single, almost vertically inclined panel is exposed to salt fog such that any salt moisture ultimately beads off of the surface of the panel), the fastened-panel salt solution would just ‘sit’ between the panels, causing way more corrosion than would be experienced on a single panel whose salt solution mostly beads and drops off.
We have very spotty success with multiple labs in passing the test, in my opinion because they don’t accurately interpret ‘evidence of galvanic corrosion’.
Any experience or guidance would be helpful. I really can’t see how the AMS organization can specify a test with such loose pass/fail criteria as that!
Mike Palatas
– Gardena, California
February 14, 2022
A. Hi Mike. Just a guess, but maybe you’re supposed to tape or mask the edges because the corrosion you are looking for is not between the two panels but on the outside of the panels?
I also agree with you that if a spec calls for some kind of testing it needs to say what constitutes passing or failing that test :-)
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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