Novel hybrid sol-gel coatings for corrosion protection of AZ31B magnesium alloy

resumo

This work aims to develop and study new anticorrosion films for AZ31B magnesium alloy based on the sol-gel coating approach. Hybrid organic-inorganic sols were synthesized by copolymerization of epoxy-siloxane and titanium or zirconium alkoxides. Tris(trimethylsilyl) phosphate was also used as additive to confer additional corrosion protection to magnesium-based alloy. A sol-gel coating, about 5-mu m thick, shows good adhesion to the metal substrate and prevents corrosion attack in 0.005 M NaCl Solution for 2 weeks. The sol-gel coating system doped with tris(trimethylsilyl)-phosphate revealed improved corrosion protection of the magnesium alloy due to formation of hydrolytically stable Mg-O-P chemical bonds. The structure and the thickness of the solgel film were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The corrosion behaviour of AZ31B substrates pre-treated with the sol-gel derived hybrid coatings was tested by electrochemical impedance spectroscopy (EIS). The chemical composition of the silylphosphate-containing sol-gel film at different depths was investigated by X-ray photoelectron spectroscopy (XPS) with depth profiling. (C) 2008 Elsevier Ltd. All rights reserved.

palavras-chave

ELECTROCHEMICAL TEST METHODS; EVALUATING ORGANIC COATINGS; TEST PARAMETER MEASUREMENTS; IMPEDANCE SPECTROSCOPY; GALVANIZED STEEL; ALUMINUM-ALLOYS; METALS; PRETREATMENTS; UPDATE; NANOCONTAINERS

categoria

Electrochemistry

autores

Lamaka, SV; Montemor, MF; Galio, AF; Zheludkevich, ML; Trindade, C; Dick, LF; Ferreira, MGS

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