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Contamination of Ti parts during cleaning or passivation

100 Ti 6AL 4v parts were made to specifications and all were from same lot of material and processed at the same time. A random 25 (25 out of the original 100 = 75 remaining) of these parts were sent to an outside vendor to be cleaned and passivated. The parts came back without any signs of contamination. Another random 25 (25 out of the original 100 = 50 remaining)additional parts were sent to another vendor to be cleaned and passivated and these also came back as expected without any signs of contamination.

The remaining parts (50) were sent to the vendor that was most responsive as he would win our future business. The problem is that the last 50 sent (remaining 50 of the original 100) came back all tarnished. The vendor could not shed any insight other than the parts must have come in to us contaminated.

To investigate the mystery, I had to send the parts to an outside SEM facility to test parts to establish the contaminant. They found high amounts of carbon on the Ti parts. Can anyone explain what could have gone wrong with what was going to be and should have been a routine clean and passivation process? Please help.

Steve Smith
industrial user of metal finishing services - Yuma, Arizona, USA
2004

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Does not sound proper. Suggest finisher had a dirty cleaner tank, and the carbon adhered to the surface. Good new is that this can be lightly cleaned off with a PROPER titanium etch and then re-passivate.

Jon Quirt
- Minneapolis, Minnesota
2004

adv.