Cleaning Aluminum: Parts Change Color

Q. What temperature should we be running for aluminum parts so they don’t change color?

A.  When cleaning aluminum, a changing color is often due to galvanic reactions with other metals that may be present in the solution or bath. You should make sure that the aluminum being cleaned is electrically insulated from other metals by cleaning in glass containers or beakers if this is being done in an ultrasonic bath or tank.  If this is a static soak, a plastic container is fine.   These recommendations are due to plastic absorbing ultrasonic energy, and is therefore not ideal for ultrasonic cleaning.

If this does not solve the problem, you may wish to try using a mild acid detergent such as Citranox® Liquid Acid Cleaner and Detergent rather than an alkaline cleaner. Citranox detergent is much less likely to darken aluminum. Of course you can also experiment with lowering the temperature if you wish to continue to use an alkaline cleaner. There is no specific temperature to avoid darkening of aluminum, but in general every 10 deg C you lower the temperature you cut the rate of cleaning, and therefore possibly the darkening in half. If there is a galvanic reaction, then lowering the temperature may not be so effective.

You can also request a free sample of Citranox cleaner or any Alconox Inc. detergent by completing the questionnaire at Get Sample.  Further details needed, or any questions at all for our technical experts?  cleaning@alconox.com