Yes phosphatizing can damage your glossy topcoat finish. It is only
recommended when you are going to prime unpainted bare steel. If you
are doing some spot repair and you don't have to take it down to bare
metal..Don't...the best prime is the paint that's already there if it is
sanded and has good adhesion.
On the other hand if you must take it down to bare metal then I would
get one of those cleaner/metalprep products and carefully apply it to
just the bare metal areas. Read the directions (and cautions) on the
container carefully. It is OK to let it get on other painted areas if
they are going to be painted eventually anyway.
For example...if you have damage on a fender, repair the damage and
sand the area smooth..while also sanding the entire fender. If you sand
thru the old primer then just use metalprep on those areas. Then prime
and topcoat the entire fender taking care to wipe the entire fender
lightly with a tack rag before and after the prime coat and sanding
lightly after the primer. I hope this makes sense!
'49 Chevy 3600
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959