Corrosion resistance investigation of epoxy siloxane/clay nanocomposite coatings

By the wide spread usage of steel, corrosion of steel has always been an inseparable concern. Among various ways to deal with this issue, organic coatings are a reasonable solution due to their ease of use and reasonable price. Among these coatings, epoxy resin is widely used because of its high mechanical strength, excellent adhesion, desirable ionic resistance and proper resistance against chemical agents. However, due to high crosslink density, the epoxy resin is quite brittle and prone to crack; therefore, many researches have done to improve the toughness of epoxy resins by modifying the formulation of epoxy resin like simply silane mixing or by means of hybrid systems through chemical reactions such as epoxy siloxane resin. Further more protective performance of organic coatings based on epoxy resin has been improved by combining with appropriate pigments and fillers. Extensive studies have been carried out to investigate the anticorrosion performance of coatings based on epoxy siloxane as well as barrier properties of composite containing nanoclay but not the synergism effect of epoxy siloxane and nanoclay in one formulation. In this study, due to the desirable properties of epoxy siloxane resin as well as clay nanoparticles, the corrosion resistance properties of epoxy siloxane / clay nanocomposite were investigated by electrochemical impedance spectroscopy (EIS). The materials used in this investigation consisted of hybrid epoxy siloxane resin, aminosilane hardner and long chain alkyl ammonium modified montmorillonite nanoclay. The desired amounts of organoclay were mixed with epoxy siloxane as reported in table 1. The coated samples were kept immersed in 3.5 wt.% NaCl solution up to 112 days and during that period the EIS data were captured. Resistive performance of the nanocomposites was evaluated at 2, 7, 14, 28, 56 and 112 days. Higher impedance values of the samples containing nanoclay, in comparison to the neat sample have been observed which reveal a more effective corrosion protection of steel substrate by epoxy siloxane nanocomposites. Investigation showed that the samples containing 2% and 3% nanoclay had more acceptable corrosion behavior in comparison with 1% and 4% nanoparticles loaded coatings. As can be seen in Fig. 1 the sample consisted of 2% nanoclay exhibited the best anti-corrosion behavior and had the lowest polarization resistance reduction (0.5%), after a long time exposure to corrosive environment.

کلیدواژه ها:

Corrosion ، Epoxy siloxane ، Nanoclay ، Organic coating ، Steel.