The protecting mechanism of zinc rich coatings is mainly based on cathodic protection provided by the zinc dust
in the paint. Cathode protection by zinc is finite; however, since after the zinc has been corroding for some time
the electrical conductivity diminishes and at the same time zinc corrosion products build up on the zinc dust
pigments and polarizes the zinc. The zinc primer still protects the steel substrate but the galvanic activity is taken
over by post-cathodic protection which is based on barrier and inhibitive protection provided by the zinc corrosion
products, also named “post-cathodic protection”. Improvement of the protecting mechanism can be obtained by
formulation with auxiliary pigments combining the effects from size distribution and packing, pigment oil
absorption, cathodic inhibition etc. A preliminary test result is given in this paper.