On Wed, 14 Dec 2005 21:11:09 -0800, Smitty Two
wrote:

In article ,
"Morgans" wrote:

"Lou" wrote in message
oups.com...
Ok, but why do I want to coat the aluminum? Is this a process just for
metal planes?
should i be doing this on my aluminum hinges attatched to my wooden
spars?

Ok,I'm no expert on painting, but I'll take both sides here

Aluminum will oxidize if left to it's own means. What the etch - alodine

Wellll, yah, kinda, sorta, but...It really depends on to what it's
exposed.

coat process does is prevent the process form continuing on it's own.

Alodine is pretty fragile and the Aluminum Oxide is pretty tough.
Unfortunately both have their weaknesses.

Aluminum protects itself. When it rusts (aka oxidizes,) which it does
very very quickly, it forms aluminum oxide (duh.) A coating of aluminum

It forms that layer which is only a few molecules thick almost
instantly.

oxide is about the hardest, most impervious thing you could put on a
piece of metal. The "process" does not "continue on its own." As soon as
a microscopically thin layer forms, your aluminum is protected from
further degradation.

Within reason I agree such as just leaving it alone


The problem arises when the exposed metal is left to water, salts,
dissimilar metals, etc, for long periods of time, which sets up

When it comes to salts it doesn't take much time. Look at the
corrosion around the joints on paint jobs with poor prep.

electrolysis. If you think you're going to protect aluminum from that
kind of damage with some kind of coating, then be my guest. I plan to
keep my plane clean and dry, and let the aluminum oxide that forms
naturally do its job.

Now, I know Mr. Morgans isn't going to flame me for these comments,
because he's already canned me, but I'd love to hear from others who may
disagree.

The Alodine process does two things. It is a prep for painting so it
gives the paint a surface to which it can grip really well.

Alodine itself is relatively fragile. It is very thin and can be
rubbed off, but between the added protection against dissimilar metals
and a good surface for your paint to stick to, I think it's worth the
effort. Give it a good primer and your paint job should last a long
time.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Jon in California