ALUMINUM ANODIZING

Industry Focus: All Industries Utilizing Aluminum Components that Require Corrosion Resistance and/or
Cosmetic Appeal—Medical, Aerospace, Oil & Gas, Semiconductor, and Automotive for Example.

Aluminum is anodized primarily for two reasons: to increase corrosion resistance and to allow dyeing.  When exposed to the atmosphere, aluminum forms a passive oxide layer which provides moderate protection against corrosion.  In its pure form, aluminum self-passivates very effectively.  However, aluminum alloys--especially 6000 series due to the magnesium content--are much more prone to atmospheric corrosion and benefit significantly from the protective oxide layer.

During aluminum anodization, the aluminum oxide layer is made thicker by passing a direct current through an acid solution, with the aluminum object serving as the anode, which is the positive electrode.  The electrical current releases hydrogen at the cathode (the negative electrode) and oxygen at the surface of the aluminum anode.  Therefore, a build-up of aluminum oxide is created, which is essentially a ceramic coating having characteristics of high hardness and high corrosion resistance.   

APT offers Type II and Type III aluminum anodizing processes, which have been perfected over the past 15 years.  The most common anodizing specification is MIL-A-8625, which defines three types of aluminum anodization. Type I is Chromic Acid Anodization, Type II is Sulphuric Acid Anodization and Type III is sulphuric acid hardcoat anodization.  Type II anodizing (room temperature) creates an anodic layer of aluminum oxide that is 0.0002" to 0.001" thick (approximately half which is grown into the surface and the other half above the surface).  By introducing dye into the anodization process, various colors can be obtained.  APT’s stringent process controls yield consistent, brilliant colors from lot-to-lot.  See images below.

Various Industrial Aluminum Products Anodized with APT’s Unique Process Technology

Type III (hard coat) anodizing is performed at much colder temperatures and at higher current densities and can reach thicknesses of 0.002" – 0.004”.  Type III anodized surfaces are commonly dyed black or dark green due to the denser pore size.

Contact Anodic Process Technology TODAY to learn how we can provide high-quality, fast delivery, and cost-effective aluminum anodizing services for your products.  Contact Us