Anodize- Anodizing

Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The plating is done through a current and is called anodizing because the part to be treated forms the anode electrode of an electrical circuit.

Anodize Coating

Anodize coating is usually used for decorative and electric purposes for it is highly resistant to corrosion. About 50% of the coating thickness is ‘absorbed’ in the base metal, therefore creating an extremely hard layer which is resistant to abrasion and can be grinded. That is the reason for which anodizing can also be used for parts that demand high engineering precision.

Anodizing Process

The process begins when a current is activated and then creates hexagonal crystals of aluminum oxide. In the center of every hexagonal there is a hole through which reagents are released in order to keep creating the oxide.

In order to supply high resilience to questioned items, these holes must be sealed at the end of the anodizing process. The process, which is defined as sealing, is performed in various ways according to standards.

Anodizing Types

Anodizing Types are mainly defined and characterized by the acids used for the anodizing process such as phosphoric acid, Sulfuric acid and different acid mixtures. Hard coat and regular coat are also considered as types of anodizing.

Anodizing Shades

        Black

        Red

        Blue

        Natural color (light gray- brown)

Custom made anodizing colors can be produced on special request

MIL-A-8625

Classification by Type

Type

Anodizing Type and Common Use

Type I

Chromic acid anodizing- Used mainly for aerospace applications

Type IB

Chromic acid anodizing- weak voltage process

Type IC

Organic acid- weak voltage process

Type II

Sulfuric acid anodizing- most commonly used anodized coating. Mainly used for decorative and engineering purposes

Type IIB

Thin Sulfuric acid anodizing- mainly in a natural shade and used as a substitute for chromic acid.

Type III

Hard coat, hard anodizing

Classified by Class

Class

Anodizing Shade

Class 1

Colorless anodized – “Natural” anodizing

Class 2

Colored anodizing – mainly black, green, red, brown or a special request shade