On the Mechanism of Formation of Conversion Titanium-Containing Coatings

The present work is devoted to the study of the mechanism of the process of formation of adhesive oxide-titanium coatings on steel, zinc, and aluminum surfaces. For the first time, the following hypothesis has been confirmed experimentally, namely, that nickel, being the first metal to be deposited on a steel substrate, creates active centers on which titanium oxides are formed, because the hydrolysis of hexafluorotitanic acid is adsorbed, which then form a continuous film. The data obtained, regarding the dependence of the coating thickness on the linear rate of the solution flow along the treated surface, indirectly confirm that the formation of insoluble titanium oxides occurs because of the alkalization of the solution adjacent to the surface. It has been established that in the presence of hexavalent molybdenum compounds in the solution as oxidizers, molybdenum is included in the coating in the form of oxides. It has been revealed that in the lower layers of the coating, molybdenum is contained in the form of compounds of molybdenum (V) and (VI), while in the upper layers, it is contained only in the form of the compound of molybdenum (VI).