There is a product you can buy down at your local ACE hardware store called
OSPHO. This is a phosphoric acid solution, green in color, and comes in
about a quart and a half size clear plastic container. I use to pre blasted
metal and wire brushed metal which will be left "naked" for a few days. Just
paint it on with a small brush, just enough to "color" the surface. Let
stand for a few minuets, and wipe off the residue. If you let it stand too
long it becomes sticky and very hard to wipe off. With bare metal prepped
this way in Florida, I can let the metal stay un-protected for well over a
month with no sign of surface rust, although I usually try to primer the
surface in a couple of days.
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