Light orange rust that blooms on bare steel soon after blasting, waterjetting or washing, especially in humid weather or where chlorides remain. Specs grade it as light, moderate or heavy, and many coatings tolerate light flash rust on waterjetted steel while immersion linings do not. Fast or heavy flash rusting is usually a clue that soluble salts are still on the surface.
Flash rust showed up within an hour of washing, test for chlorides before anybody primes over it.
Also heard as
- flash rusting
- rust bloom
- turning
Related terms
Soluble salts
Invisible chloride, sulfate and nitrate contamination on steel that causes blistering and early coating failure.
Dew point
Temperature at which moisture condenses from air; specs keep steel at least 3 C above it for blasting and painting.
White metal blast
Top abrasive blast cleaning grade: bare, uniform steel with no visible residue, rust or staining.
Near-white blast
Blast grade allowing light shadows or stains on no more than 5 percent of the surface, the usual immersion standard.