Zero Rust DTM Primer is a direct to metal primer designed for use over bare metal or rusted metal to form a barrier which keeps oxygen and moisture away from the metal to stop rust growth. Zero Rust has been tested to withstand over 2000 hours of salt spray with excellent results. Top-coating is optional, however the color of Zero-Rust will fade when exposed to ultra-violet light from the sun. This does not effect the corrosion resistance properties.