From: Tony King - W4ZT <amps080605@w4zt.com>
To: Amps <amps@contesting.com>
Subject: Re: [Amps] Pretreatment of Aluminum for painting
Date: Thu, 13 Oct 2005 03:01:57 -0400
Alodine is a chromate conversion process which does provide a conductive
surface. It is widely used in military gear and in a huge number of
aircraft. It is recommended for electrical and electronic use because of
its corrosion resistance and electrical conductivity. It is far superior
to spraying zinc chromate on aluminum. It's relatively safe to use and
readily available in quantities we can use at home and at a reasonable
price. It leaves the unpainted surfaces an attractive gold color which
is very corrosion resistant and which doesn't show finger prints like
untreated aluminum.
See this link: <http://www.poly-metal.com/alodine.shtml>
73, Tony W4ZT
N7KA@comcast.net wrote:
> I do believe ALODINE provides an insulating surface. The best
preparation of aluminum for paint processes is a chromate surface. This is
accomplished per MIL-C-5541 (ANSI has a different specification number for
thsi process). This is a conductive surface treatment and normally yields
the light yellow to brownish color depending upon length the parts are
subjected to the chemical conversion process.
> The process is usually done with a series of tanks used to clean, coat,
and rinse parts. There are 2 classes of coatings based upon the
requirement for a very low surface resistance (Class 1A) or a normal
conductive surface (Class 3). Some chemical conversion can be performed in
clear color and must be specified.
> There is a new process that does not use chromates that we are
investigating at work. Because of the heavy metal attributes of chromate
we do NOT do this process ourself, but send it out to be done. A
non-chromate process would allow us to do it in-house and save a lot of $$
and lessen use of chromates (hopeful eliminate 99% of our chromate use
requirements).
> I do some painting of aluminum at home and usually get good results by
ensuring the surface is clean of any oils. I clean with alcohol and use
several light coatings of paint. Most I then bake in the oven at about
170F, let your wife go away for the weekend, or she might get very upset at
this happening in HER oven. Often after this I will allow the part to
relax in the New Mexico sun to continue in a natural baking process. The
paint hardens very nicely.
> If I can find a shop that does powder coatng (and does it within hobby
budget) I will have all projects painted in this manner. Powder coat is
probably the best commercial coatings available.
> I may have digressed a bit but hopefully the info will be helpful to the
readers. I am sure others have had success with other processes. I for
one would be interested in other results.
> 73 de Arne N7KA
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