In many instances, a primer will provide significantly improved
properties for the application, and therefore more than justify
any additional cost.
Primers are applied after proper
surface preparation (discussed in the following chapter) to
enhance adhesion, improve resistance to corrosion and to chemical
attack.
The primers tend either to be
highly pigmented or are filled with materials that inhibit corrosion
and chemical attack, depending upon the specific requirements
of the application in question. These primers work by slowing
down the anodic, cathodic or diffusion reactions.
Anodic reaction is suppressed
by pigments specially chosen to provide cathodic protection
or by surface passivation. These formulations are generally
highly loaded.
Cathodic protection is provided
by zinc-rich primers which are sacrificial, and which are designed
to corrode more readily than the substrates they cover.
