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Re: Rust

Hi Dave;

    I run Audi painted alloys in the winter and have used the same
techniques I have listed to repair the salt corrosion, except I use a brush
for spot repair instead of a spray gun. It gets more difficult with the
clear finish alloy wheels  because you cannot use the epoxy and urethane
primers; it is the primer that provides most of the corrosion protection.

    The M3 metal conditioner I use can be used on alloy wheels, but it
sometimes gives a "rainbow" tint to the metal surface. This doesn't matter
if you are painting, but I don't know what would happen if you clear-coated
over it. Try a small area of your wheel to see what happens; you can always
sand it off to bare metal again. The metal treatment will go a long way to
giving you a durable job; as well as passivating the metal; it cleans and
chemically etches the surface to give the paint better grip. Check the
literature on the product before you buy to make sure it is compatible with
aluminum/magnesium alloys.

    As for the clear finish, I would try a good two-part urethane clearcoat.
This is the finish used as the topcoat on modern cars and it is very
durable. It is usually available in regular, fast-dry, and hi-build formats.
The hi-build product is designed to go on heavy, giving thicker layers of
paint; you might want to try this for your wheels. The only acceptable way
to apply this stuff is with a spray gun, although it can be successfully
brushed on to small areas if you are experienced (and fast; you've got to
get it right the first time - use a slow reducer if you are going to try
this!). If your wheels are clearcoated over the white paint, you can
clearcoat the whole wheel. Prep by washing with a silcone-wax remover, wet
sand with 600 grit, solvent clean & spray.


Fred Munro
'91 200q
-----Original Message-----
From: Dave C. <conner@cfm.ohio-state.edu>
To: munrof@isys.ca <munrof@isys.ca>
Date: Saturday, January 24, 1998 11:34 AM
Subject: Re: Rust

>Nice post on Paint steps.
>I wonder if you can tell me the best way to touch up my alloy wheels?
>They are two tone, mostly white paint with shiny metal around the outer rim
>area.  The white paint looks great but the 1 inch wide shiny part is
>shabby.  It seems the clear finish is about half gone and it takes a lot of
>work to shine it up.
>I'm thinking of stripping just this part to bare metal.  Would the
>phosphoric acid based metal conditioner be suitable for surface prep?
>What clear finish is suitable for use directly on the metal?
>I'd appreciate any suggestions you can make.
>> 2.    Treat the bare metal with a phosphoric acid-based metal
>> 3.    Base prime with an epoxy-based wash primer such as Dupont Corlar.
>> 4.    Top prime with a two-part urethane primer such as Dupont 1020R.
>> 5.    Topcoat with good quality paint. I find Dupont's Chromabase
>basecoat/clearcoat system easy to use,
>Columbus, OH
>89 100 w/ 85 k miles
>87 5KS w/ 116 K miles, w/ new bomb
>86 4KQ, w/ Konis and retarded timing (tooth jumped)