Type I Chromic acid anodizing is a frequent anodizing system preferred by the US government for anodizing aluminum parts that are to be riveted together or that form lap joints. Because chromic acid does not attack aluminum, thorough rinsing and neutralization of the acid is not critical in the joints. There are many chromic acid bath formulations. Many are proprietary and may be licensed.
Generally, two acid concentrations are used; 3% and 10% chromic acid. The higher concentrations are for thicker oxides while the lower concentrations produce a harder and more compact oxide. There is little difference in the operation of the bath as the concentration is increased above 10%.
Unlike sulfuric acid anodizing, the oxide thickness produced is much thinner, seldom approaching 0.5 mil maximum.
The chromic acid bath uses stainless steel cathodes at a cathode to anode ratio of 1:5. The 3 % bath is operated at 104º F while the 10% bath operates at 129º F. The average current density is about 3 amps per square foot (3 asf).
If the parts are to be inorganically colored, the anodizing time should be restricted to less than 30 minutes.
The chromic acid bath is very sensitive to chloride and sulfate contamination. The bath should be operated with a chloride content of less than 0.02% and a sulfate content of less than 0.05%.
Types of Anodizing:
Type I Chromic Acid Anodizing
Type II Commercial Anodizing
Type III Hard Coat Anodizing
Titanium Anodizing
Impregnation
 Packaged Chillers Non-expandable (integrated pump tank) 1.5Ton – 20Ton Single / Dual Circuits Single / Dual Pumps |
 SAE Series Modular Chillers Expandable (pump & tank on separate skid) 1.5Ton – 200Ton Single / Dual Circuits |
 SAR Series Split Chillers Expandable (Outdoor Condensing Unit) (pump, tank, evaporator on indoor skid) 1.5Ton – 200Ton Single / Dual Circuits |