Process Study Based on Aqueous Silane Polymers and Ti/Zr Composite Chemical Transformation Technology on Various Metal Surfaces

Abstract

In this study, 6061 aluminum alloy, 7075 aluminum alloy and galvanized steel were investigated as research subjects. Through the optimization of an waterborne epoxy based silane polymer combined with fluorotitanic acid and fluorozirconic acid composite chemical conversion process, the corrosion resistance of the three metals was concurrently enhanced. The corrosion resistance of the film layer was explored using electrochemical performance testing and copper sulfate spot-drop experiments, and the micro-morphology and elemental composition of the conversion film were characterized and analyzed by combining scanning electron microscopy(SEM) and energy-dispersive X-ray spectroscopy(EDX). Finally, the film formation mechanism of the titanium zirconium silane composite conversion film was explored. Results showed that when the optimal process formulation was selected, namely waterborne silane WB100 at 2.7%, H2TiF6 at 2.2 mL/L, H2ZrF6 at 1.0 mL/L, a conversion time of 90 s, pH of 3.7, and a temperature of 40 ℃, the surfaces of the composite conversion films on various metal materials were uniformly dense and exhibited superior corrosion resistance. The film formation mechanism analysis revealed that the initial titanium zirconium silane composite conversion film evolved through three stages, ultimately forming a bilayer structure composed of metal oxides and organic monomolecular films.

Keywords

• fluorotitanic acid and fluorozirconic acid composite converison film; polymetallic; corrosion resistance; silane