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Sandblasting considerations

To: Victor Hughes <hughes@scides.canberra.edu.au>,
Subject: Sandblasting considerations
From: "jumpin'jan" <servaij@cris.com>
Date: Tue, 11 Dec 2001 18:54:23 -0800
Victor,
        Well, here are few comments on sandblasting:
1. Media will surely be trapped inside the body shell. It is impossible
to get it all out before any painting, so during painting it gets blown
out of it's hiding places and gets in the paint, making MORE WORK. Also,
water can be trapped in the sand media and promote more rusting.
Furthermore, you will find little piles of sand from time to time in the
body.
2. A careless and inexperienced sandblasting shop will ruin the body
sheet metal by warping the sheet metal, making more work. This is a
major risk!
3. Body cleaning is not complete. Since the blasting operation uses low
air pressure and the blaster tip is moving more and further away from
the surface, it never gets to gray metal. If they did, than metal
warpage is more frequent. Result is one has to remove further rust and
other contaminants. This is especially prevalent on the underside
structure areas. Since, the body needs to be flipped upside down, they
overlook some areas because of visibility and effort required. Some
shops are very careless lifting/flipping the body. Metal will be bent
and can very easily damaged where it can't be pulled back and
straighten.
4. Areas that are not accessible, are not cleaned. What happens when one
starts to remove rusty body panels? The inner structure is also rusty
and grimy. Guess what? More work.
5. Rust is not fully removed. The dipping is a chemical process that
should remove the oxidation. Blasting is a mechanical process and it's
performance is dependent on operator experience and equipment settings.

Anyway, there are some reasons that I recommend people to avoid doing
it. Blasting a body will appear very cheap and quick, but you are
trading money for your time/labor and materials.

When I receive an Alpine body from the dippers, I experience NONE of the
detriments from above and I'm ready to start welding in new panels.
Jan
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