New Corrosion Inhibitors Based on Perylene Units in Epoxy Ester Resin Coatings

Four new compounds from perylene dianhydride were prepared and tested for their anti-corrosion properties. Dizinc salt of perylene-3,4,9,10-tetracarboxylic acid and dimagnesium salts of perylene-3,4,9,10-tetracarboxylic acid, 5,5 '-(1,3,8,10-tetraoxo-1,3,8,10-tetrahydroanthra[2,1,9-def:6,5,10-d ' e ' f '] diisoquinoline-2,9-diyl) bis(2-hydroxybenzoic acid) and N,N '-bis[3,3 '-(dimethylamino)propylamine]-3,4,9,10-perylenediimide were characterized by analytical methods (SEM, EDX, X-ray) and parameters used in the field of paints (density, oil number and critical volume concentrations of pigment). The pigments (in a pigment volume concentration series) were used to prepare paints also containing a perylene C26H14N2O4 (Compound I) derivative pigment plus inert titanium dioxide to maintain a constant concentration of solids in the paint film. A mixture containing zinc nitroisophthalate and both the perylene derivative and titanium dioxide served as the reference material. The paints were applied to steel panels in two layers with a ruler. The organic coatings were subjected to electrochemical measurements and accelerated cyclic corrosion tests. The highest corrosion resistance was found for the coating containing C24H8O8Mg2. Superior to the coating containing either C26H14N2O4 or the conventional corrosion inhibitor C(8)H(5)N0(6)-Zn, this pigment type acted mainly by a mechanism based on the compound's complexation capacity at the metallic surface/organic coating/corrosion medium interface. The organic coatings containing perylene acid salts also attained high mechanical resistance.