RUST-OLEUM Self-etching primer is designed to prepare bare metal, aluminum and fiberglass surfaces to promote maximum adhesion and smoothness of the topcoat finish. self-etching primer is a rust preventive coating that etches and primes in one coat. Self-etching primer features an advanced spray system that allows you to spray at any angle, even upside down for those hard-to-reach areas. A comfort spray tip with a wider finger pad reduces fatigue caused by continuous spraying.