On Wed, 27 Apr 1994 lesnyd@bb1t.monsanto.com wrote:
> The place I really need to do some good on is the bulkhead/firewall behind
>the
> engine. It has quite a bit of rust, although, as I said in an earlier
>message,
> I believe there's still lots of metal there, except for the battery tray.
>
> What is the best means, either abrasive or chemical, of removing this rust?
>Is
> there such a thing as localized sandblasting? Can I rent one and do that? I
> have lots of outdoors to do something like that...
>
Certainly you can sandblast small areas; the problem is to confine the
mess to a small area--the sand will go all over. But that isn't really a
huge problem, just do it outdoors. Do not sandblast on a gravel driveway,
with the expectation that the sand will become one with the driveway. I
thought it would, but it just sat there, defying rain and wind, being
tracked into the house, until I hired a front end loader to scrape it away
and spread new gravel. We live and learn. On grass is better; if you
don't overdo it, it will disappear into the ground. But a drop cloth
right under the job to catch large accumulations is a good idea. A pile
of black sand will kill grass. I have tried sandblasting in the garage,
hoping to recover and reuse the sand, and the mess is enormous. It is
especially something you don't want to do in an area where you hope later
to apply paint.
There are essentially two kinds of sandblasters, siphon type (cheap) and
pressure type (more expensive). For a one-time fairly small job, the
former will work ok, albeit slowly--very slowly. Pressure type is better;
the tank is pressurized and the feed is more reliable. They work much
faster and use less air. Each type requires a compressor, preferably
something over 2 or 3 HP. For the smaller compressors, reducing the
nozzle size will help the compressor keep up.
Don't use ordinary sand; it is not at all good for your lungs. It also is
not very uniform in size and will plug the nozzle every 20 seconds or so,
leading to considerable cussing. Use the best breathing apparatus you
can, and use a slag product sold for sand blasting. I used something
called Black Beauty. You can sift all of the media before using it, to
eliminate any large bits that can clog the nozzle, but this requires the
patience of Job. I used it from the bag, and it only clogged the nozzle
once in a while. Finally, don't be tempted, even for a few seconds, to
touch up a spot without facial protection. I did once, reasoning (if you
can call it that) that my regular glasses would protect my eyes. They
did, but were pitted immediately by the sand. One $200 pr of glasses,
gone--but it could have been an eye.
I tried sandblasting hoods, and the lens fogged up quickly from my
breathing. In Missouri, in the summer, I don't think you would be able to
see for long. In fact, in Missouri in the summer, the lens probably would
be foggy on the dealer's shelf. Eventually, I settled on a shower cap, a
good respirator, and a full-face shield such as one uses for grinding.
(It's funny, nobody seems to sell a shower cap without flowers or ferny
designs so I always tried to sand blast when I did not expect visitors,
for I cut a pretty funny figure with my face all black, grit all over me,
and a daisy print shower cap. But I digress.) I covered the shield with
plastic food wrap, which I could change frequently, or else just used it
until the shield became opaque and replaced it. Put foam ear plugs in,
not so much for the noise, as to keep sand out. You'll want heavy leather
or rubber gloves, too, because a pressure sandblaster can draw blood.
Last, but not least, harmony between you and your significant other
probably requires that you do this job just once, finish it, strip off in
the garage, walk to the shower gingerly so as to dislodge as little sand
from your hide as possible, then shower for a very long time, scrubbing
vigorously. Non car nuts, whatever their sex or sexual orientation,
rarely agree that the sense of accomplishment compensates for the trail of
black sand through the wall-to-wall.
Thus speaketh the voice of experience, after about 2 tons of sand.
Ray Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons@northpole.med.uvm.edu (802) 656-8910
|