Use for Metal Roofs that have been painted with epoxy, latex or oil based paints that our coating will not bond to. This primer will bond to a painted surface or roof coated with Rust Inhibitors and then allows our roof coating to bond to it. Do not use this on a Roof Coating, it is intended to be applied to painted surfaces only. We recommend power washing painted surface and removing any loose paint, let roof dry thoroughly and apply 1 coat of primer. 1 gallon covers aprox 400 square feet.