Abstract

BANCZEK, Everson P.; OLIVEIRA, Marilei F.; CUNHA, Maico T.  and  RODRIGUES, Paulo R.P.. Study of the Electrochemical Behaviour of Tolitriazole in Phosphating Bathings of Carbon Steel 1008. Port. Electrochim. Acta [online]. 2005, vol.23, n.3, pp.379-391. ISSN 0872-1904.

The characteristics of corrosion inhibitors of the tolitriazole (TTA) for the carbon steel 1008, covered by zinc or tricationic phosphate (Mn, Zn, Ni), in the means of H₂SO₄ 0.1 mol L^-1 and NaCl 0.5 mol L^-1, were investigated by physical and electrochemical methods. The results obtained in the absence of the inibidor TTA showed that the corrosion protection properties of the tricationic phosphate (Ptri) are better than those observed for the zinc phosphate (PZn), probably due to the presence of vacancies in the layer of PZn. The curves of anodic polarization presented current densities (j) smaller for the steel phosphatized with Ptri, when compared with the metal substrate without phosphate and with PZn. The results of impedance electrochemistry (IE) showed a polarization resistance (Rp) larger for the electrodes phosphatized with Ptri. The electrochemistry measurements of the samples of steel phosphatized, with PZn and/or Ptri, in the presence of [TTA] = 1x10^-3 mol L^-1, present smaller j and larger Rp when compared with the absence of TTA. In the process of phosphatization of the carbon steel with PZn + TTA, it was observed similar j and Rp in the samples of steel phosphatized with Ptri without TTA. These results suggest that the bathing of zinc phosphate with [TTA] = 1x10^-3 mol L^-1 can substitute the well known industrial bathing of tricationic phosphate. Corrosion testing by Salt Spray of steel phosphatized with PZn and PZn + TTA, painted with white polyester ink, confirmed the eletrochemical results.

Keywords : tolitriazole; corrosion; phosphatization; inhibitors.

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