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Anodizing
Hot Salt Bluing \ Color Case Hardening \ Fire Blue \ Nickel, Silver and Gold Plating \ Slow Rust Bluing \ Stainless Steel Bluing \ Mil-spec Parkerizing \ Anodizing \ French Gray
If you are looking for a tough, protective coating but also want a unique finish,
anodizing may be what you are searching for. Anodizing is an electro-chemical process
that converts the surface of raw aluminum to an artificial oxide coating. Anodizing
is not a plating process because, unlike plating, anodizing doesn't deposit any
material onto the metal surface. It is actually a complex series of steps involving
pre-cleaning, etching, deoxidizing, anodizing, dying and sealing with careful rinsing
after each immersion. Most types of aluminum can be anodized, the purer grades
producing a better finish.
The process involves placing aluminum in an electrolyte, sulfuric acid, and passing
a low voltage current through it. The aluminum part is connected to the positive
anode and the negative anode is connected to a lead cathode, which causes the aluminum
to oxidize, similar to the process of steel rusting. This results in the formation
of a very hard, tough and abrasion resistant protective coating. The most exciting
feature of anodizing is the amazing array of colors and effects that can be produced.
Following immersion in an organic dye, parts are sealed with a nickel acetate seal,
which literally closes the pores of the anodized coating, preventing the dye from
leaching and the anodic film from deteriorating.
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