DO NOT DO IT. Afriend of mine did it a few years in his aluminum sailboat
and had to replace all the aluminum after the galvanic action destroyed
it.(within three years) YOU may be very sorry. The aluminum becomes the
destructive anode rather than the other way around. I know this seems
conterintuitive, because it is used in aircraft, but aircraft are not
constantly immersed. Even though you state that it's the inside of the
pontoon, it could and probably will cause problems. Whats wrong with the
bare aluminum? Efflouresence? Deeply etched? Ever try lightly wiping bare
aluminum with a little ATF (red automatic transmission fluid) to seal the
surface? It works OK and it's cheap. Consult the paint manufacturer if you
want to go with the zinc chromate, there could be a special surface prep
step as well as thinning instructions. Remember, aluminum oxide on the
surface is the protectant for the substrate and unless it comes in contact
with stuff like battery acids, it does corrode but at a very slow rate.
Proceed with caution and good luck.
wrote in message
oups.com...
I need to coat the inside of an aluminum pontoon with zinc chromate, in
order to do this it must be thinned. What solvent can be used to thin
zinc chromate?