Summary for mil-5541 alodine discoloration Discussion
Discoloration of MIL-5541 Alodine is discussed as a likely result of lifting parts too slowly after dipping, allowing chemical to flow over the surface and stain it. Morgan Mao of Taiwan explains that their shop uses a crane to dip more parts at once, but the slow pull-up seems to trigger the problem, and extra water spraying does not help. Robert H Probert replies that the issue appears to be the slow lift speed itself and asks why the parts cannot simply be raised faster. He suggests that speeding up the withdrawal may solve the discoloration, and also invites Morgan to send photos for posting if desired. The thread does not offer a more detailed process fix, but the practical advice centers on reducing dwell time during lift-out to prevent runoff marks.
June 10, 2022
Q. Hi, everyone
I am Morgan form Taiwan, and currently we are running a surface treatment shop.
We are now having the discoloration issue for the Alodine process.
We use the crane to do the dipping process for our product.
The advantage of the crane is that we can do more parts at once. But it pulls up the part at a very slow speed. When we pull up the part, the chemical flows over the part and causes the discoloration. Even if we keep spraying water on the part, it doesn’t help.
Can anyone give us some suggestion?
Thank you in advance for the help.
Morgan Mao
– Tainan Taiwan
A. Hi Morgan. Apparently you’ve figured out that the problem is a lift speed that is too slow, but send photos to finishingdotcompublic@gmail.com for posting if you wish.
It’s not clear to me why you have to lift very slowly. Why not simply speed it up?
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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June 2022
A. I suspect the film is forming too fast due to low pH, high temp or high concentration. In a beaker, try raising the pH in increments of 0.1. This will slow the film formation, get it to about 90 seconds, then see if that helped the problem until you can do the recommended Mooney thing and speed up the hoist.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
June 13, 2022
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