Anodizing

Anodizing Process

Anodizing non-ferrous metal parts results in a controlled layer of oxide coating. Usually performed in a sulfuric acid solution, this coating increases corrosion resistance and insulation.  The anodizing process is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of aluminum parts. 

Anodizing increases corrosion and wear resistance and offers greater retention of adhesives, primers, and lubricants than bare aluminum. The corrosion resistance of anodizing will decrease with the presence of impurities such as copper, iron, and silicon in the aluminum alloy. Anodic films can be used for cosmetic effects by applying a thick, porous coating that can absorb dyes and prevent the galling of threaded components. 

Furthermore, anodized coatings are also nonconductive. They have a lower thermal conductivity and coefficient of linear expansion than aluminum and a higher melting point.

Types of Anodizing Processes

The most widely used Anodize specification is Mil-A-8625, which defines three types of aluminum anodize:

Chromic Acid Anodizing (Type 1) – The primary advantage of chromic acid anodizing is self-healing, has good corrosion resistance properties, and will not damage or fatigue the aluminum.

Sulfuric Acid Anodizing (Type 2) – Type 2 is the most common anodizing process, ranging from 5 to 15 microns. Sulfuric acid anodize is inexpensive and can be easily dyed.

Sulfuric Hard Anodizing (Type 3) – Type 3, also known as hard anodizing, allows for a coating thickness of up to 75 microns. Hard sulfuric acid anodize has a hardness of up to 70 Rockwell and can also be dyed.

Industries That Utilize Anodizing

Anodizing is used on a variety of aluminum products; aircraft parts, architectural materials, and many consumer products such as flashlights, cooking pans, and MP3 players, and in the defense industry on guns, tripods, robotics, and other components.

Contact the Anodizing Experts at Silvex, Inc.

Silvex can certify thicknesses of anodized parts to +/- 5 microns. The deep pores created by anodizing make it an ideal application for anything requiring adhesion. To learn more about our anodizing process, please contact us at Silvex today.