This is the corrosion inhibitive coat applied to restrict corrosion at steel surface. The concrete surface does not need such primers. Instead a clear coat can be applied to seal the pores to make it non-absorbent. The rust inhibitive primers contain various anticorrosive pigments like Red Lead, Zinc Chromate, Zinc Phosphate and Zinc Dust. Besides anticorrosive action primer helps improve adhesion of the subsequent coat.

These tow coats provide strong barrier to atmospheric condition to protect the primer coat. The primers due to high PVC have poor exterior durability. If primer is not over-coated, the inhibitive pigment in the primer will become active and the rate of inhibitive reaction will be very high and therefore, the entire pigment will be consumed very fast reducing the effective life of primer. When it is over-coated with intermediate and finish coats, either nil or negligible quantity of oxygen and moisture penetrates the film and corrosion inhibitive reaction would be at much lower sped extending the life of primer.

There is an increasing trend of formulating products suitable to give one coat finish at higher film thickness to suffice instead of two separate products i.e. for intermediate and finishing coats.

As the finish coat is applied to protect the primer coat, the finish coat also needs to be protected from the atmosphere with which it is in direct contact. By the virtue of its being the last coat, it has to be self-protecting and therefore the ingredients used in the finish coat have to be so chosen that they resist the action of the atmospheric conditions. The high performance coatings are therefore designed to be resistant to ultra violet

rays and atmospheric pollutants such as high humidity salinity acid & alkalis, etc. the finish coat should posses the following properties: