Custom Anodizing – What is it?
ANODIZING, WHAT IS IT?
Anodizing successfully combines science with nature to create one of the world’s best metal finishes.
It is an electrochemical process that thickens and toughens the naturally occurring protective oxide. The resulting finish, depending on the process, is the second hardest substance known to man, second only to the diamond. The anodic coating is part of the metal, but has a porous structure which allows secondary infusions, (i.e. organic and inorganic coloring, lubricity aids, etc.).
Definitions and Methods
While the chemical anodizing process remains the same for all applications, the mechanical methods vary according to the two physical types and shapes of metals used:
Involves racking parts and immersing them in a series of treatment tanks. Extrusions, sheets or bent metal parts, castings, cookware, cosmetic cases, flashlight bodies, and machined aluminum parts are just a few of the items that are batched anodized.
Continuous Coil Anodizing
Continuous coil anodizing involves continuous unwinding of pre-rolled coils through a series of anodizing, etching and cleaning tanks, and then rewinding for shipment and fabrication. This method is used for high volume sheet, foil and less severely formed products such as lighting fixtures, reflectors, louvers, spacer bars for insulated glass, and continuous roofing systems.
Appearance options and quality are improved through the use of dyes and special pretreatment procedures. This makes the aluminum look like pewter, stainless steel, copper, brushed bronze or polished brass and can also be colored with brilliant blues, greens, reds, and many varieties of metallic gold and silver.
The unique dielectric properties of an anodized finish offer many opportunities for electrical applications.
The surface of the aluminum itself is toughened and hardened to a degree unmatched by any other process or material. The coating is 30 percent thicker than the metal it replaces, since the volume of oxide produced is greater than that of the metal replaced.
The resulting anodic coating is porous, allowing relatively easy coloring and sealing.
Hard Anodizing is a term used to describe the production of anodic coatings with film hardness or abrasion as their primary characteristic. They are usually thick by normal anodizing standards (greater than 25 microns), and they are produced using special anodizing conditions (very low temperature, high current density, special electrolytes). They find application in the engineering industry for components which require a very wear resistant surfaces such as pistons, cylinders and hydraulic gear. They are often left unsealed, but may be impregnated with materials such as waxes or silicone fluids to give particular surface properties.