Re: Anodized planes ?

Date:         27 Aug 99 03:08:17 
From:         Ken Ishiguro <kenish@earthlink.net>
Organization: EarthLink Network, Inc.
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  or MIME structure

Many of the individual bits and pieces of an aircraft are anodized.  The
internal structure is usually coated with a chromate primer (the pea soup
green stuff).  It's tough and resists corrosion.

Anodization does change the surface of the part.  However, it must be done
to the entire part.  In the case of skins, the sheet would have to be
anodized, and during the process of forming, bending, drilling, and
riveting  the skins, the anodize would probably crack.  Also, anodize is
an electrical insulator, which is not good when you want the fuselage to
be electrically bonded.

The usual process for external skins is to use Alclad sheets. Alclad is
aluminum alloy coated with almost pure aluminum.  The outer aluminum forms
a thin "crust" of aluminum oxide, which protects the aluminum beneath.
For other parts, a process called Alodyne is used.  The aluminum is
chemically etched, and the Alodyne is painted on.  It chemically converts
the surface and makes it more corrosion resistant.  Alodyne is usually
gold or greenish in color, and M-D for one used it extensively.

A last note about anodize is it would be difficult to repair once
installed.

Ken Ishiguro