Comparison of steel anticorrosive protection formulated with natural tannins extracted from acacia and from pine bark

Research studies were carried out using AISI 1010 (UNS G10100) steels, trea ted with tannin primers formulated with natural tannins extracted from Chil ean radiata pine species and from Brazilian black acacia, Steels were previ ously blasted, followed by a surface chemical reaction with tannin solution s free from glues, yielding reaction products of 5 mu m thickness. Afterwar d, conventional anticorrosive paints were applied on triplicate probes whic h were evaluated in a salt fog chamber according to ASTM B 117-73 and ASTM D 714-56 standards, and in potentiodynamic scanning tests. The results indi cated that pine tannins present better reactivity than acacia tannins, with better corrosion inhibition and better adherence to metallic substrates. I t is generally demonstrated that conventional anticorrosive paints or the p ainting schemes applied on steel previously treated with a primer formulate d with pine tannins, extend the duration of painting schemes in more than 5 0% than without this chemical treatment. (C) 2000 Elsevier Science Ltd. All rights reserved.