Summary for dissolved oxygen anodizing Discussion
Dissolved oxygen in type III sulfuric acid anodizing is raised as a possible cause of slow anodizing after long continuous runs. Scott Frazier said his high-production line runs 24/7, but after about 72 hours he sees cooling problems, longer anodize times, and a lot of air in the tank; samples also take minutes to clear. His chemical rep told him the solution was oxygen buildup in the bath, which he said acts as an insulator and slows anodizing, and suggested reducing air sparging or letting the tank rest. Scott noted that when the system is allowed to rest for a few hours, performance returns to normal, and another anodizing manager had seen the same issue. The excerpt does not include a technical explanation or a definitive answer from Ted Mooney, only the problem description and the rep’s suggested remedy.
Q. I hoping someone can explain to me exactly what dissolved oxygen is (in a sulfuric type III anodizing solution) and how to control it. Not exactly sure what other information to ask for. Thank you.
Scott Frazier
– Spokane Valley, Washington
May 12, 2016
Hi Scott. I think what may be left out is where you heard of it and why you’re concerned about it :-)
I’m personally not familiar with anybody measuring or trying to control dissolved oxygen in an anodizing operation.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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May 2016
Q. Thanks Ted. Our line can run 24 hours, seven days a week. We do high production, type III anodizing. When we reach 72 hours of straight running time, we have trouble with cooling and anodize time in the tank. After extended run times (about 72 hours), we do notice an excessive amount of air in the tank. When we take our samples for testing, it takes a few minutes for the air to clear out of the sample jar. I explained this to our chemical rep and he said it’s oxygen build up in the solution and it works as an insulator and will slow the anodizing times down. His solution was to reduce the air sparging in the tank or let the tank rest for a few hours.
When we let the system rest, everything goes back to normal. Spoke to another anodizing manager and he has seen the same issue but never knew what it was. I’m open for suggestions and thank for your response Ted,
Scott Frazier [returning]
– Spokane Valley, Washington
May 12, 2016