A primer with a high loading of zinc dust, often over 80 percent by weight in the dry film, so the particles touch each other and the steel and corrode sacrificially to protect scratches and pinholes. Inorganic zinc silicates last longer and take more heat but demand careful application, while organic zinc epoxies are more forgiving. Either one is usually the base of a multi-coat system on bridges, offshore structures and plant steel.
Shop puts the zinc-rich primer on after blast, epoxy midcoat and urethane go on in the field.
Inorganic zinc must be fully cured, commonly checked with a solvent rub test, before topcoating, or the topcoat can bubble and delaminate.
Also heard as
- zinc primer
- IOZ
- inorganic zinc
- organic zinc
Related terms
Hot-dip galvanizing
Coating steel by dipping it in molten zinc, forming bonded zinc-iron layers that protect by barrier and sacrifice.
Mud cracking
Network of cracks like dried mud in a coating applied too thick, typical of inorganic zinc and waterborne paints.
Near-white blast
Blast grade allowing light shadows or stains on no more than 5 percent of the surface, the usual immersion standard.
Galvanic corrosion
Accelerated corrosion of the more active metal when two dissimilar metals touch in a shared electrolyte.