Cleaning Aluminum without Corrosion

Q. How is galvanic corrosion prevented when cleaning aluminum?

A. Aluminum is an active metal that is somewhat high on the “anodic index” of the galvanic series. If aluminum is cleaned with other metals present, you can create a battery and get galvanic corrosion. Aluminum should not be cleaned in the presence of metals that are significantly higher or lower on the anodic series; higher on the anodic scale such as zinc, magnesium or beryllium metals and lower on the anodic scale such as tin, brass, bronze, copper, silver, nickel and rhodium.

Galvanic corrosion is facilitated between aluminum and other metals that may be dissolved in the cleaning bath from prior cleaning, or present in the cleaning bath during the time of cleaning. The corrosion can take the form of a dark grey film or deposit, a brown film or deposit, and with more exotic metals, other colors are possible. Certain cast alloys of aluminum can have galvanic corrosion problems with cast iron, carbon steel and low alloy steels.

Note that intact and properly passivated stainless steel does not have a problem with galvanic corrosion on aluminum during normal cleaning. The Alconox Inc. brand cleaners recommended for cleaning aluminum are Alconox® Powdered Precision Cleaner, Liquinox™ Critical Cleaning Liquid Detergent, Alcojet® Low Foaming Powdered Detergent, Detojet™ Low Foaming Liquid Detergent, Luminox® Low-Foaming Neutral pH Liquid Detergent, Solujet™ Low-Foaming Phosphate-Free Liquid, Tergajet™ Low-Foaming Phosphate-Free Detergent, Tergazyme™ Enzyme-Active Powdered Detergent, Citranox® Liquid Acid Cleaner and Detergent, Citrajet® Low-Foam Liquid Acid Cleaner/Rinse, Alcotabs® Tablet Pipet Detergent.  Detergent 8® Low-Foaming Ion-Free Detergent is not recommended for cleaning aluminum.

Aluminum that has been exposed to the environment often forms a characteristic dull grey surface oxide. None of the recommended cleaners will remove this and brighten the aluminum again. The recommended cleaners are intended for use in removing residues, not surface oxides that are bound in to the aluminum matrix. To clean this type of aluminum, there are very hazardous strong acid cleaners that can sometimes be effective. Alternatively, there are mild abrasive cleaners that can be used to polish the dark coating off the aluminum surface. Alconox does not make any of these kinds of cleaners.

To test an Alconox, Inc. detergent for free, please complete the questionnaire at Get Sample.