Tannins are polyphenols synthesized by plants and useful for the coating industry as corrosion inhibitors. In addition, lanthanum salts have a great inhibitory effect on steel corrosion. The aim of this study was to obtain lanthanum ''tannate'' with adequate solubility to be incorporated as the corrosion inhibitor in a wash-primer. The ''tannate'' was obtained from commercial ''Quebracho'' tannin and 0.1 M La(NO 3 ) 3 . The soluble tannin was determined by the Folin-Denis reagent, while the concentration of Lanthanum was obtained by a gravimetric procedure. The protective action of ''tannate'' on SAE 1010 steel was evaluated by linear polarization curves and corrosion potential measurements. Lanthanum ''tannate'' was incorporated in a wash-primer formulation and tested by corrosion potential and ionic resistance measurements. The corrosion rate was also determined by the polarization resistance technique. Besides, the primer was incorporated in an alkyd paint system and its anticorrosion performance assessed in the salt spray cabinet and by electrochemical impedance spectroscopy. Results showed that lanthanum ''tannate'' primer inhibits the development of deleterious iron oxyhydroxides on the steel substrate and incorporated into a paint system had a similar behavior to the primer formulated with zinc tetroxychromate.
Steel panels must be protected during storage and transportation because they can corrode. This protection used to be afforded by chromate primers, but nowadays tannin-based primers are being studied. These primers are not only used as protection but also as adhesion promoter if the steel surface was not well prepared (presence of oxides or low roughness). The objective of this work was to prepare lanthanum "tannate", employing tara and quebracho tannins. The "tannates" were incorporated in primers formulation and applied on steel SAE 1010 panels (previously exposed to the humidity chamber or with 6 μm of roughness depth). These primed panels were exposed to humidity chamber where corrosion and blistering degrees were evaluated. Adhesion test were done. Electrochemical assays such as ionic resistance and corrosion potential measurements were carried out. Results showed that the adhesion and the barrier properties of the primers were good. Besides, on low roughness steel, the primers diminished the corrosion current. Results were compared with traditional zinc tetroxychromate primer.
Tannins are extracted from certain plants and contain numerous phenol groups. They may be employed, together with their derivatives, to formulate protective coatings due to their inhibitive properties. The objective of this research was to synthesize lanthanum "tannates", to formulate washprimers. Two "Tara" (Caesalpinia spinosa) tannins and 0.1 M La(NO 3) 3 were employed to obtain the corresponding tannates. The inhibitive action of the tannates was evaluated by linear polarization and corrosion potential measurements employing a SAE 1010 electrode. Lanthanum tannates were used to formulate wash-primers whose anticorrosion performance was evaluated by corrosion potential and ionic resistance measurements. The primers were incorporated in alkyd paint systems and their anticorrosion performance was tested in the salt spray chamber and by electrochemical impedance spectroscopy. Lanthanum tannate primers protected steel and behaved in a similar way to that formulated with zinc tetroxychromate.
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