Influence of Tetraethoxysilane Addition in Siloxane-Poly(Methyl Methacrylate) Hybrid Films Applied on Galvanized Steel

Abstract

Hybrid films of siloxane-poly(methyl methacrylate) (PMMA) are used as coatings in materials such as galvanized steel and alloys and have also recently been used as bulk materials. To improve the performance of these films, new formulations have been developed with the introduction of plasticizer agents to improve zinc corrosion resistance and to increase the layer thickness in order to more evenly coat the rough surface of galvanized steel. In this context, the aim of this paper is to coat galvanized steel with a hybrid film of PMMA and a mixture consisting of the alkoxides 3-(trimethoxysilylpropyl) methacrylate (TMSM) and tetraethoxysilane (TEOS). The hybrid films were applied by dip-coating and curing for 3 hours at a temperature of 160 °C. Samples with and without TEOS were characterized by electrochemical impedance spectroscopy (EIS), and the open circuit potential was monitored in a 0.05 M NaCl solution. The hydrophobicity of the film was determined by contact angle measurements. Morphological aspects were evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). FT-IR measurements were recorded to characterize the films. The mechanical behavior was evaluated by tribology trials of attrition. The results obtained for the T4AN01 film showed a higher thickness associated with the presence of TEOS in the film, which increases the silanol content and, consequently, the amount of inorganic phase (siloxane). The EIS results showed that the T4AN01 coating displayed the best performance.