Flash Rust Inhibitor FRI-200 (Amine/Zinc Salt Type)

Flash rust is the rapid formation of visible iron oxide (rust) on bare or lightly prepared steel surfaces within minutes to hours of applying a waterborne coating. It occurs because waterborne primers contain water — which is corrosive to steel — and many lack the passivation chemistry of solvent-borne systems. Flash rusting is most severe on contaminated or minimally-prepared surfaces (e.g., Sa 1–2 blast or power tool cleaning), in humid conditions, or with coatings having long flash-off times. A flash rust inhibitor passivates the metal surface by forming a protective complex (e.g., amine-iron chelate or zinc phosphate-type layer) that prevents initial oxidation during the critical wet-film period. FRI-200 is added at 0.5–2.0% to the waterborne primer formulation.