"Dave Rupert" wrote...
> I'm having a flash rust problem..... <snip>
If you're using a commercial (ie DuPont, RM, PPG, etc.) metal prep, they
have directions for dilution, which should be followed, although I've had no
problem doubling the concentration from label dilution (some's good, more's
better !!). They usually recommend a damp rag or water wash to neutralize
the prep, not lacquer thinner, although thinner doesn't sound offhand like
it'd cause worse flash rusting. Remember, however, that thinner has a large
percentage of alcohol in it, and alcohol tends to take on water from the
atmosphere, so you are wiping with a partially-water material anyway. Or
you might be taking in the water from the acid solution into the thinner ??
Anyway, you're SUPPOSED to wipe or wash the prep off with water !!
If you wish to take the next step after metal prep, get some conversion
coating. It's got phosphoric acid like metal prep for additional cleaning,
but also adds more agents to promote iron phosphate production. I'm not a
chemist, and don't really remember what's going on chemically, but DuPont
and others have products for this and I usually use them. DuPont's is a
2-step process, using their 223S and 224S - I have skipped the 223S step and
used 224S right after prep, but your dealer will know for sure. This should
eliminate MOST of your flash rusting, although you will likely see some
BEFORE conversion coating - that happens with prep despite what the label
says you should expect. I always follow up with an inhibitive primer like
Corlar or an aircraft product called GlidPlate. Those do a fine job on
un-prepped steel, so any prepping is to the good despite flash rusting. I
DO wipe off any loose flash rust, gray coating, etc. with a CLEAN, DRY rag
prior to painting anyway. Oh yes - be careful with the dust from
overspray - the inhibitive primers generally use chromates (zinc, strontium,
or etc.) and these can cause lung cancer if inhaled. It's generally an
industrial-use issue and may not be a problem for a casual user, but why
take a chance, especially if you have kids around.
I just read the reply regarding using Prep Sol, etc. I had a problem with
painting a repair on my (then NEW) TR-6 in '71 because I wiped with Prep-Sol
just before painting, and then shot the paint. The jobber laughed at me
when I took in a 12" sheet of paint I'd blown off the car at the quarter car
wash - Prep-Sol leaves an oily film that takes a VERY LONG time to dry. If
you want to solvent wipe, use a fast-dry enamel reducer or something made
just for a final solvent wipe to make sure you're not leaving any residue on
the surface. DuPont makes a product specifically for this (3939S), although
I prefer the enamel reducer myself.
Bottom line is to find a GOOD professional automotive refinish jobber and
buy your stuff there. They will give you the right information and products
to do it properly the first time. DuPont, PPG, etc. are all good
manufacturers - the jobber is the key to getting you the right product and
application information. Anything less is just not doing justice to all
your hard work.
Good luck !!
- Karl Vacek
'66 TR4A - IRS
'64 Amphicar
'16 Ford T Touring
'46 Piper J-3 Cub
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