Letter 20102

Is clear Alodine more conductive than colored? [Pennsylvania] 

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In using the Alodine method on aluminum enclosure, is clear Alodine more conductive then yellow Alodine for electrical grounding??

Rich Tadrzynski
medical - Telford, PA, USA

Absolutely!

Bill Grayson
- Santa Cruz, CA, USA

I have never seen any data to backup any claim that clear is more conductive than yellow chromates. Because you can achieve a clear from a yellow chromate simply by bleaching the yellow color from the part after chromate.

So I would say no that there is no substantial, measured difference in the two. Now if the chromate is a true clear, than the possibility might exist, but again I have my doubts. Best bet is to contact the supplier of the chromate and ask them directly. They should know, and if they don't know, then assume what I said, that the answer is no.

Matthew Stiltner
- Toledo, OH

In general terms, the lighter the chromate, the less the resistance (greater the conductance). A note of caution, however, there are two ways to get a clear chromate: using a true clear as deposited chromate and depositing a yellow / gold chromate and leaching it out with hot water. The latter will have greater resistance than the first.

Measuring the resistance or conductance of these films is tricky. It's highly dependent on age of the coating, pressure used, humidity, etc. In would seem that defining a standard procedure to measure this property would be straight forward, however, it's seldom done!!

Milt Stevenson, Jr. Anoplate Corp Syracuse, NY, USA

Well, we had a yes, a no, and a maybe on that one :-)

I think that's the first time we've had such a diversity of opinion so concisely stated.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

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