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 H 2 SO 4 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.
RESUMODevido às inúmeras aplicações do aço carbono na indústria, torna-se necessária a utilização de tratamento de superfície para controle e prevenção da corrosão deste metal. Um dos sistemas utilizados como pré-tratamento do aço carbono para posterior pintura é a fosfatização à base de zinco, a qual permite melhorar a ancoragem da tinta sobre o substrato metálico. No entanto, este tratamento gera para a indústria um passivo ambiental relacionado ao lodo e ao íon metálico alergênico e poluente utilizado no processo, neste caso o Ni 2+. O objetivo deste trabalho é desenvolver e caracterizar um tratamento alternativo ao fosfato de zinco para o aço carbono 1008, utilizando-se um fosfato orgânico. O método utilizado foi o de imersão do substrato metálico em uma solução aquosa de uma molécula orgânica à temperatura ambiente. Os corpos de prova do aço carbono foram avaliados utilizando-se microscopia óptica e eletrônica de varredura, espectroscopia Raman, ensaios eletroquímicos de polarização potenciodinâmica anódica e espectroscopia de impedância eletroquímica em meios ácido e neutro, além dos ensaios em Salt Spray. Os resultados eletroquímicos e de corrosão acelerada mostraram que o filme de fosfato orgânico minimiza a corrosão no aço carbono, podendo ser utilizado em substituição ao tradicional fosfato de zinco. Palavras-chave:Molécula auto organizável, fosfato de zinco, tratamento de superfície. ABSTRACTDue to the numerous applications of carbon steel in industry, the use of surface treatment to control and prevent the corrosion of this metal becomes necessary. One of the systems used as pre-treatment of carbon steel for subsequent painting is zinc phosphating, which allows to improve adhesion of ink onto the metal substrate. However, this treatment causes an environmental liability to industry, related to the silt and allergenic, pollutant metal ion used in the process, in this case Ni 2+. The objective of this work is to develop and characterize a treatment alternative to zinc phosphate for the 1008 carbon steel, using an organic phosphate. The method used was that of immersing the metal substrate in an aqueous of an organic molecule at room temperature. Specimens of carbon steel were evaluated using optical microscopy and scanning electron microscopy, Raman spectroscopy, electrochemical tests of anodic polarization and electrochemical impedance spectroscopy in acidic and neutral medium, besides the Salt Spray tests. The electrochemical and fast corrosion
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