Sufluric Anodize

Sulfuric anodize, commonly referred to as Type II anodizing, if formed by using an electroolytic solution of sulfuric acid at room temperature and a current density of 15 to 22 amps per square foot. The process will run for 30 to 60 minutes depending on alloy used and desired thickness. This will product a generally clear coating, depending on sealing, of at least 8 microns thick. One third of the coating thickness will build up and 2/3 will be penetration.

Properties

Type II sulfuric anodizing provides for several desirable qualities such as:

• Corrosion Resistance ( 336+ hours salt spray per ASTM B117 )
• Moderate Durability
• Excellent Coloring
• Electrical Insulation

Sulfuric anodize coatings are often sealed to enhance corrosion resistance, lock in dyes, or both. Hot water seals produce the clearest seals while sodium dichromate yields a yellow-green appearance but is generally a better seal. Nickel acetate seals offer a good compromise between clarity and effectiveness.

Specifications

There numerous government, industrial, and commercial anodizing specifications in use, each with there own method of calling out anodize types, seals, dyes, etc. Most anodizers should recognize the Type II designation to indicate a conventional sulfuric anodize, Class 1 to specify a natural color or no dye, and Class 2 to indicate a dye.

Suitable Alloys