Abstract

ALVARADO-MACIAS, Gabriela; FUENTES-ACEITUNO, Juan Carlos; SALINAS-RODRIGUEZ, Armando  and  RODRIGUEZ-VARELA, Francisco Javier. Understanding the Nature of the Manganese Hot Dip Phosphatizing Process of Steel. J. Mex. Chem. Soc [online]. 2013, vol.57, n.4, pp.328-336. ISSN 1870-249X.

Abstract In this work, the phosphatizing process of steel is investigated using open circuit potential and Tafel curves as well as scanning electron microscopy and energy dispersive X-ray spectroscopy. The results reveal that a pH of 2.57 in the phosphatizing solution promotes the dissociation of phosphoric acid which assists the formation of the manganese tertiary salt (Mn₃(PO₄)₂), which is deposited on the substrate. It was also observed that an increase in the temperature from 25 to 90°C and the presence of HNO₃ as catalyst enhances the manganese phosphatizing kinetics. On the other hand, the generation of iron phosphates and oxides is predominant at a pH of 1 and 90°C. These observations are supported by species distribution and Pourbaix thermodynamic diagrams.

Keywords : Tafel; Phosphatizing of Steel; Coatings; Pourbaix; Manganese.

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