Letter 22026

Alodine 600 rinsing question  

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Alodine rinsing question: At my work the procedure for rinsing parts pulled out of the Alodine 600 tank is to rinse them with a water faucet, which is directly over the Alodine tank as opposed to doing a dip rinse. My question is, wouldn't this remove the Alodine before it sets in? Also wouldn’t this cause an excess of contaminates in the Alodine bath? The reason the shop floor does this is they were instructed by our environmental people to reduce the 55 gallons of Alodine rinse water that is disposed of every other week. I believe this was a $250.00 cost to dispose of a 55-gallon drum of Alodine wastewater.

Any suggestions would be appreciated.

Steve Shoenberg
- Long Beach, California, USA

Hi Steve,

The rinse after chemical treatment is a necessary step, but the conversion coating will not be rinsed off. The coating is being formed when the parts are in the Alodine bath and is deposited on the aluminum surface.

The other part of your question, however, is a bit tricky. Rinsing the parts while they are over the Alodine tank is asking for trouble, IMO. The chemical composition of the bath is set up that way for a reason. Adding water and reaction products back to the bath will, over time, probably compromise the bath's ability to deposit coating effectively. You may be saving money in the short term by not having to deal with disposal of the rinse water. But in the long term, the Alodine bath will probably have to be dumped sooner than normal and the coating that it produces on the parts may be of lower quality.

George Gorecki
- Naperville, Illinois 

Chromate conversion tanks are normally unheated or very minimally heated, so the evaporation loss is nearly non-existant. This hose water must therefore cause the chromate conversion tank to overflow in short order. This change sounds a bit penny-wise.

Go back to doing it the right way. If you can make room for two rinse tanks, you probably will need to dump far less frequently since you don't need to dump until the first gets so contaminated that it continues chromating.

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

 

Thank you for the fast response. So far rinsing parts over our Alodine tank has not caused an overflow problem. Actually it has not appeared to effect the level of the tank at all. However, my gut feeling is that this is not the right thing to do. The pressure I am receiving is from the environmental people due to the fact that they do not want to constantly dispose of rinse water. In the past the procedure was to dump the rinse water every two weeks which to me sound like over kill. Is there a way I can test the rinse water to insure that I am only disposing of it when absolutely necessary? Again this is the rinse after the Alodine 600 bath.

Steve Shoenberg
- Long Beach

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