3M™ Scotch-Weld™ Metal Primer EC-3901 is a one-component, silane-based primer formulated specifically for aerospace applications in California (Aerospace Use Only). It promotes superior adhesion of epoxy and urethane structural adhesives to both metal and glass substrates by creating a micro-molecular bonding layer (<0.0001 in/2.5 μm) that ensures complete wet-out of the adhesive to the adherend surface
. EC-3901’s low-viscosity formulation applies easily by spray or brush, air-drying at 75–85 °F (24–33 °C) for a minimum of one hour (or force-drying at 190 °F/88 °C for 30 minutes), and helps protect cleaned surfaces against oxidation and corrosion during production delays
. The primer increases resistance to environmental exposure with both epoxy and urethane adhesives, simplifies production scheduling by maintaining surface readiness until bonding operations are completed, and delivers long-lasting performance in harsh aerospace environments