OPTIMIZATION OF METALLIC PIGMENTS IN COATINGS BY AN ELECTROCHEMICAL TECHNIQUE AND AN INVESTIGATION OF MANGANESE POWDER AS PIGMENT FOR METAL-RICH PRIMERS

Zinc dust and manganese powder as pigments were incorporated in epoxy- polyamide and butyl titanate medium, with different pigment volume con centration (PVC) ranging from 20 to 74. These protective coatings were coated on sand blasted mild steel substrates and immersed in 3 wt.% s odium chloride solution and the corrosion current was measured by the Tafel extrapolation method. From the corrosion current produced by the se primers, the optimum level of the pigments in these binders was ide ntified. Thus the protective performance of optimised primers was eval uated on a sand blasted mild steel surface by the Tafel polarisation m ethod in 3 wt.% sodium chloride solution, over different periods of ti me. The results were found to be comparable with the salt spray test a nd galvanic current measurements. The manganese powder used for this i nvestigation showed that it could be used as an alternative to zinc po wder for metal rich primers.