Seawall rust treatment and thinned enamel paint applied with garden sprayer

Ospho by Skyco is a metal surface preparation treatment using phosphoric acid. For rusted metal, OSPHO is a rust-inhibiting coating, not a paint.

You do not have to remove light rust. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush. 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. When applied to rusted surfaces, it resists/retards rust in chemical change on drying to a tough, hard surface ready for priming.

Once the Ospho has dried, the enamel paint must be thinned for the garden sprayer application. Then clean the sprayer thoroughly with mineral spirits before applying the second coat next time.