We have found and are working on our motor mount rust.
"RUSTED METALS - OSPHO is a rust-inhibiting coating - NOT A PAINT You do not have to remove tight rust. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush - apply a coat of OSPHO as it comes in the container - let dry overnight, then apply whatever paint system you desire. When applied to rusted surfaces, OSPHO causes iron oxide (rust) to chemically change to iron phosphate - an inert, hard substance that turns the metal black. Where rust is exceedingly heavy, two coats of OSPHO may be necessary to thoroughly penetrate and blacken the surface to be painted. A dry, powdery, grayish-white surface usually develops; this is normal - brush off any loose powder before paint application."
The rest of the instructions can be found on the OSPHO web site.
So we have done the wire brushing and some sanding and applied the OSPHO .
After 24 hours we will paint!
We purchased a pint of gray rust preventive paint from a local paint store here in Puerto Vallarta.