ADVANCEMENT IN ZINC RICH EPOXY PRIMERS FOR CORROSION PROTECTION

摘要

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.