I want to spray in a bedliner for my F150. I have some dents and places where paint is missing. What do I need to do to prepare for spraying SL&C truck bed liner?
Truck bed-type surfaces and other areas such as jeep and truck exterior surfaces (or any surface with automotive paint) needs no general sanding if the paint is in good condition. Spray Lining and Coatings and Diamondback Linings brand Truck Bed Linings and Exterior Vehicle Coatings adhere well to these areas. Light scuffing is always advised to dull the surface. You should always clean any oils or other contaminants with acetone or lacquer thinner first before lightly sanding.
Unpainted metal surfaces are recommended to be primed before application in general. Regular steel can sometimes be successfully coated with only scuffing. Primers are always recommended on non-porous surfaces which have no current auto or marine grade coatings applied. Any automotive grade one to one epoxy primer or other high quality primer will suffice for most metals. PPG Spectracom 701-702 is generally recommended for bare aluminum.
Preparing other surfaces for protective coatings:
In the case of fiberglass, primer is not generally required. Out-gassing can sometimes be an issue if the material has not fully cured yet however. For newer fiberglass surfaces, appropriate primer is usually recommended.
Wood, cement substrates, all porous stone, et cetera require a clean surface which is free of oils or loose materials, but generally do not require a primer. It is often advisable to apply a light coating first and let it cure for at least 1 hour before applying additional coats in order to establish a solid base for the full build application.