Primers are perfect for coating rough, previously sandblasted surfaces.
A primer fills uneven spots on a rough surface, making the finished surface appear nice and smooth.
Primers are not designed to protect surfaces against different external factors; primers are well-suited for surfaces which do not need protection from corrosion, such as pre-treated indoor parts, etc.
Zinc-rich primers are suitable as an underlay for surfaces that need corrosion protection.
Powder-technology based priming is often used, for example, in urban environments on metal barriers, doors, posts, and garbage cans. This is especially relevant to coastal areas.
Zinc-rich primers are often also used to coat metal parts for vehicles, such as tin wheel rims, frames, bridge parts, bars, etc.