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Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Anodizing color variations in a single profile

June 22, 2019

Q. My friend who lives and works in Iran has an interesting problem. He needs support to solve his problem. He told me his problem:
Each pair of profiles are actually same profile. It was cut as (half and half) and put side by side as you see. One part of the profile is the nd of profile; the other part of the profile is the beginning. As you see there are obviously color differences between each part of profile . But how can explain this situation? I suspect electrical problems but all electrical details were checked and fixed. All rectifier connections between tanks were tightened. Also cathodes inside of tank were tightened too. Despite of all these controls we could not solve this problem, and we have not found the source of the problem. How can we get rid of this problem? Have you any advice?

60967-1a 60967-1c 60967-1e 60967-1b 60967-1d

Alaattin Tuna
- Turkey,sakarya

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

A. Hi Alaattin,

As always, when a regular contributor has a problem, it's usually a thorny one, with no obvious answers, hence why responses may be a bit slow coming!

So, if all of the electricals are sorted and your friend is confident that there are no problems there, about the only thing I can think of is localised heating. Have a look at how much agitation is present, is it even along the whole length of the bath? Is the air fed from one end, with the air agitation reducing as you go along the bath?

Brian Terry
Aerospace - Yeovil, Somerset, UK
July 24, 2019

July 2019

Sounds like a very good possibility, Brian, thanks! People tend to think of agitation systems as being intended for general mixing, but in the case of anodizing, the agitation being able to provide localized cooling at all points on the profile can be crucial.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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