Ospho 605 Metal Treatment, 32 Fl Oz (Pack of 1)

When applied to rusted surfaces, it resists/retards rust in chemical change on drying to a tough, hard surface ready for priming. Paint jobs will last longer after an application of OSPHO because subsequent paint coating securely attaches itself so that moisture and oxygen normally do not attack the metal. Water-thin, covers a larger area than paint and goes on easily. Equally effective for exterior or interior. Available in Case Quantity only.
A rust-inhibiting coating is 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