Metal finishing Q&As since 1989
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Titanium Color Anodizing caused severe material loss
Q. e recently sent parts to our supplier for Titanium Anodize (AMS 2488 Type II). The parts after the process were blue in color and seems like there was at least .001" material removal since the threads, inside and outside diameters are undersized! What could have caused this? We expected a Greyish color finish and no material removal. Any input will help.
Ali Motamedi- Canoga Park, California
2003
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A. Sounds like someone had a run away etch tank. I cannot go into detail here as these processes are trade secrets. You should not have experienced 0.001" removal however.
Jon Quirt- Minneapolis, Minnesota
2003
A. Sounds like you got acid anodize as your titanium looks just like my titanium racks used to sulfuric acid anodize aluminum parts. This isn't the CAUSTIC anodize clearly called for by AMS 2488, Type II.
Indeed you are correct, they should be matte gray in color. Lastly, they should have seen little, if any, dimensional change. Again, my guess would be they went through the firm's conventional anodize pre-treatment cycle used for anodizing aluminum. This would typically include a nitric acid with bifluoride (or hydrofluoric acid ); this is a pickle (i.e. etch) for titanium. I suggest that you spot audit your supplier. Ask him for a copy of the spec called for in your PO. Ask for a copy of his traveler or process map for AMS 2488. My guess is that he has neither.
AMS2486, ISO 8080, ASTM B600 and ASTM F86. Titanium is too expensive to trust to some "garage shop."
Milt Stevenson, Jr.
Syracuse, New York
2003
adv.
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