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

Abstract

Research studies were carried out using AISI 1010 (UNS G10100) steels, treated with tannin primers formulated with natural tannins extracted from Chilean radiata pine species and from Brazilian black acacia. Steels were previously blasted, followed by a surface chemical reaction with tannin solutions free from glues, yielding reaction products of 5 μm thickness. Afterward, conventional anticorrosive paints were applied on triplicate probes which 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 indicated that pine tannins present better reactivity than acacia tannins, with better corrosion inhibition and better adherence to metallic substrates. It is generally demonstrated that conventional anticorrosive paints or the painting schemes applied on steel previously treated with a primer formulated with pine tannins, extend the duration of painting schemes in more than 50% than without this chemical treatment.