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Anodizing Systems
Type II: Commercial Anodizing
(Room Temperature Anodizing)
Sulfuric acid anodizing has been defined as “an electrochemical process that intentionally forms a porous anodic oxide on aluminum”. This oxide, an integral part of the metal, is formed when a current is applied to the aluminum parts in a sulfuric acid anodizing bath.
Type II anodizing is by far the most popular form of anodizing aluminum. Everything from high rise buildings to space ships has either been completely anodized or has anodized components as part of their makeup.
Under normal circumstances, the aluminum is anodized using a prescribed set of parameters:
Typically, Type II anodizing is performed in a sulfuric acid bath containing 180-200 grams per Liter of acid and a small amount of dissolved aluminum. The operating temperature is controlled between 68-72º F. Current densities can range from 5-18 amps per square foot (ASF), but commonly are run at 12-15 ASF.
The power supply is a DC rectifier. The aluminum part being anodized is made the anode (or positive pole) in the system. The most efficient cathodes (or negative pole) are 6063t6 aluminum.
Current is applied to the system for a prescribed time, and at the desired current density to achieve the oxide thickness required (oxide thicknesses can range from 0.1 mil to 0.8 mil). The resulting porous oxide can then be colored or sealed.