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Titanium Anodize - AMS 2487 and 2488 Solution Differences

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Q. Is there a more precise way to define the requirements for titanium anodizing that could be used instead of AMS 2488 [affil link] ? That spec is not really sufficient for control of the results of an anodizing process. Is there another standard spec or additional requirements that can be placed on a vendor to assure reliable and repeatable AMS 2488 [affil link] treatment. For example, could hardness or other post-process tests be required on each lot? I am working as a consultant with a company that has received anodized titanium samples from two different coating vendors, both of whom supposedly met the AMS 2488 [affil link] spec, but the wear resistance of the films from the two vendor is very different.

Francis E. Kennedy
Professor, engineering school - Hanover, New Hampshire, USA
2006


A. The AMS 2488 [affil link] is purely for the aerospace wear test of a combined Titanium anodic coat and dry-film lubricant. You are absolutely correct that it has no sufficient control of the results of an anodizing process, especially for the medical implants.

Kas Amadi
- Dayton, Ohio
2006




Q. The seeming differences between AMS2487 [affil link] and AMS 2488 [affil link] titanium anodize specifications appear to be in the solution pH and the test requirements. 2487 requires solution pH maximum of 12.4 and has a lot more testing requirements (galvanic corrosion, foil, voltage breakdown, electrical resistance, taber) than does the 2488, which specifies a pH minimum of 13.0 and for non-propellant exposure parts, only Taber testing.

Can anyone tell me what the reason is for the solution pH specification differences between the 2487 and 2488 specs? I have anodized titanium parts using the higher pH 2488 solution (in my tank, about 13.3), and then subjected the anodized test panels to all of the 2487 testing, and they have passed all of the tests with no problems.

Is there an issue with exposing some titanium alloys to too high a pH - perhaps causing metallurgical degradation or something else? Does the pH difference have any engineering effect on the quality of the part/anodize coating?

Mike Palatas
- Los Angeles, California, USA
November 18, 2011


A. Hi Mike
I am not familiar with the specs you quote but in my opinion any pH measurement over about 11 is meaningless. Even at 9-11 special electrodes are essential.
High pH solutions should be controlled by titration.

geoff smith
Geoff Smith
Hampshire, England
November 21, 2011




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