Architectural Class I and Class II Anodize 

Class I and Class II anodic coatings are designations created by the Aluminum Association for the purpose of codifying the specification of anodized aluminum.                      

Class I coating has a mil thickness of 0.7 (18 microns) or greater

Class II coating has a minimum mil thickness of 0.4 (10 microns)

Class I coating is a high performance anodic finish used primarily for exterior building products and other products that must withstand continuous outdoor exposure.

Class II coating is a commercial anodic finish recommended for interior applications or light exterior applications receiving regularly scheduled cleaning and maintenance such as storefronts.

Coating thickness can be measured by an "eddy current", a nondestructive test instrument, or by cutting a cross-section of the anodized aluminum, mounting it in a slide, polishing the edge, and reading the coating thickness directly with a microscope. 

Class I and Class II coatings should not be confused with Type I, Type II, and Type III anodic coatings as described in the authoritative anodizing standard, MIL-A-8625. Type I anodize refers to chromic acid anodizing. Type II is normal "clear" sulfuric acid anodizing. Type III is "hardcoat" using sulfuric acid or mixed chemistry electrolytes.

Coating Weight Specification:                                 Class I >+ 15.5 mg/in²                                                                 Class II >= 27.0 mg/in²

Coating Density:                                                      Class I & II >= 38.0 mg/in³

Class I = ANO215

Class II = ANO204

For weathering and finishing performances please see our  Finish Performance Comparison - Paint and Anodize