Abstract

D’ALESSANDRO, O. et al. Quebracho colorado chaqueño (Schinopsis balansae) tannin as a precursor of a corrosion inhibitor for low carbon steel. Quebracho (Santiago del Estero) [online]. 2018, vol.26, n.1, pp.31-39. ISSN 0328-0543.

The various tannins of Quebracho colorado chaqueño (Schinopsis balansae) have been studied as an alternative for the effective protection of steel from anticorrosion to replace the traditional pigments containing hexavalent chromium which is highly questioned for its toxicity and carcinogenicity. In this work, temporary primers containing Quebracho colorado tannin and lanthanum “tannate” as anticorrosive pigments were applied over SAE 1010 steel samples. The lanthanum “tannate” was obtained by precipitating Quebracho tannin with a lanthanum salt at controlled pH. The anticorrosive behavior of the wash-primers was assessed by incorporating them in a complete painting scheme made out of an anticorrosive alkyd paint and a finishing alkyd one. The electrochemical characterization was carried out by measuring conductivity to determine the ionic resistance (Ri), using linear polarization tests to determine the polarization resistance (Rp) and measuring the corrosion potential (Ecorr). The working electrodes used in the electrochemical tests were observed through a Scanning Electron Microscope (SEM) to characterize the different surfaces in their final state while the composition of the protective film was determined by Energy dispersive X-ray spectroscopy (EDS). The results show that incorporating tannin and lanthanum "tannate" primers to the complete painting scheme provides acceptable anticorrosive properties, comparable to those observed when zinc tetroxychromate formulated primers are used. From the EDS analyses it is concluded that primers promote the adhesion of the next paint layer.

Keywords : Quebracho tannin; wash primer; corrosion; SAE 1010 steel.

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