Zinc-rich primer
Zinc-rich primer turns up in 2 fields: corrosion, powder coating. Here is what it means to the people in each one.
Zinc-rich primer in corrosion
Primer loaded with zinc dust that protects steel galvanically as well as acting as a barrier.
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."
Zinc-rich primer in powder coating
Epoxy powder primer loaded with zinc dust to give steel extra corrosion protection under a topcoat.
These primers carry a high load of zinc that helps protect steel at scratches and chips and slows rust creep under the film. They are applied over blasted steel and given a partial cure before the topcoat goes on. Zinc-rich powder is used on outdoor structural steel, trailers and coastal equipment.
"Coastal job, so blast, zinc-rich primer, then the superdurable over it."