I'm finding some of what I am reading about rust converters a little unsettling.
Especially since I just spend a great deal of last weekend refinishing TR3 parts
I finished in fall of '89 and sat aside until I was ready to install them.
What I originally did:
I stripped all the paint & all the rust except what was in the bottom of the
pits. Then I coated the part with rust converter. I followed it up with
rustolium primer and rustolium black paint. 4-1/2 years later, these parts were
blotchy with rust forcing me to take them down to bare metal & starting over
again.
What I do now:
Mechanically remove all paint and rust. Where there is pitting I hit it with a
sand blaster to clean the pit out. The part immediatly gets brushed or if it is
very small soaked in a phosphoric acid pre-paint metal etch. This chemically
converts rust and adds a protective coat. I brush the phosphoric acid across
the metal so that fresh acid will be moved against the metal to keep the
chemical reaction going (A trick I learned in developing B&W film). Then I dry
off the part (if its small it goes into the oven for a short time). I follow
that up with primer & a sealer of some kind. The directions say you can wash
off the treatment with water, but I have noticed that after doing this and
drying the part, I end up with a slight redish brown coating that looks like the
first hint of surface rust. So I stopped washing off the treatment. I just
wipe it off with a dry towel. I accidently learned the value of the phosphoric
acid produced coating. Something came up one weekend while I was preping parts
and I accidently left two cleaned parts out. One was cleaned to bare metal
only, and the other treated with phosphoric acid. It was close to a month
before I found these parts again. The untreated one had a nice coating of
surface rust. The treated one, looked like I had just finished treating it.
Some odds & ends I picked up dealing with the TR3 & rust:
1. The rust converter stuff only sticks to rust. It generally does not adhear
well to bare shiney metal (remember the directions say to loosen the lose rust
but not take it all off). Moisture can easily get under any converter covering
shiney metal. This results in rust under the dried converter. Also paint only
adhears as well as the layer attaching to metal.
2. Practical Classics Mag. made a study on rust converters. One of the things
they did was cutthrough rust pits after adding converters. What they found is
that the converter does not penitrate rust. This means it converts the surface
of the rust and leaves live rust below in deep pits. It relys upon its seal to
keep oxygen from getting to the rust.
3. Body fillers are porus to water. The worst thing you can do is wet sand
fillers or rust converter. Its guarrenteed to promote rust below the
filler/converter. I had to take my boot floor back down to bare moon crater
metal and refinish it because I read someplace that wet sanding was the best way
to get a good smooth finish. Cost me a LOT of hours each time I finished the
boot floor. Second time I was hydrophobic.
4. Primers are, as a rule hydrophyllic. After a short time they will start to
absorb water and allow it to get to the metal below and start rust. Some
primers can be mixed in a way as to become a sealer. This allows you more time
to put the final moisture barrier, the colour coat, on the car.
5. Undercoating adhears better to a painted surface than to an unpainted
surface. Also, if a rock is kicked up against the undercoating creating a
pinhole, rust will not start if a painted surface is exposed. If a pinhole is
created on undercoating over bare metal, rust will start under the undercoating.
This will loosen the adjacent undercoating allowing the opening to grow larger.
6. Always read the label on paint cans and never apply paint below the
recommended level. Not only does the paint take longer to cure, and sometimes
not cure properly, but the paint will not flow properly. The result is tiny
pinholes that can pass moisture. Paint well withing the recommended temperature
and use multiple thin coats if painting from a low pressure spray can. Little
pin holes are an invitation for rust withing a couple of years. This has been
hard on me since I live on the coast and there are only a few days a year it
gets warm enough to spray most paints properly.
7.Wire brushes will just remove loose things. Do not rely on them to getting
all the rust off anything. It'll get the lose rust off and make the remainging
rust shiney.
Of well enough ranting
TeriAnn
TeriAnn Wakeman One of these days, I'll be old enough that
twakeman@apple.com people will stop calling me crazy and start
LINK: TWAKEMAN calling me eccentric.
408-974-2344 TR3A - TS75519L, MGBGT - GHD4U149572G, 109 - 164000561
|