ABSTRACT
In this research, an attempt has been made to evaluate the effect of surface modified nano-Fe2O3 particles on the anticorrosion and adhesion properties of epoxy coatings. Nano particles are treated by 3-aminopropyltriethoxysilane (APTES). Epoxy coatings loaded by various amounts of nano pigments are implemented on mild steel substrates. FTIR technique is used to assess the formation of chemical bonds on particles’ surfaces. Dispersion of nano pigments in epoxy matrix is studied by UV-visible, FESEM, and EDS techniques. Anticorrosion and adhesion properties of nano composites are evaluated by EIS and Pull-off. Results showed that grafting of aminosilanes is successfully accomplished on nano particles surfaces. Nano iron oxide particles are dispersed uniformly in the epoxy matrix due to the surface modification process. In addition, anticorrosion and adhesion properties of coatings containing nano particles increase remarkably especially in the presence of 3%wt nano iron oxide.
INTRODUCTION
Mild steels are widely used in various industries due to their proper mechanical properties and low cost. They, however, are susceptible to corrosive environments [1-3]. Therefore, the surface protection of plain steels is required against corrosive elements. Applying organic coatings is an efficient method to reduce corroding of such steels [4-6]. Epoxies are common resins for organic coatings applied for corrosion resistance applications due to their high corrosion, chemical, and thermal resistance [7-9]. Nevertheless, there are various defects and pores in organic coatings structures, by which aggressive ions can reach the interface of metal-coating and cause substrate to corrode as well as organic coatings disbanding and delamination [10-12]. Hence, most protective coatings exhibit an undesired degree of permeability against corrosive elements [13, 14].
Applying pigments is able to suppress permeation of corrosive elements and enhance corrosion resistance of organic coating by several mechanisms such as barrier mechanism [15, 16]. The barrier pigments prevent penetration of corrosive elements by filling defects and pores. Parameters such as shape, size, amount, and dispersion of pigments severely affect the barrier property of coatings [17, 18]. It is reported that flake-like pigments have a superior barrier property than spherical and cylindrical shapes [19, 20]. Additionally, pigments increase penetration resistance as their average size becomes smaller. As a result, nano particles have exhibited to be more effective barriers than micro particles in the coatings because of higher specific and surface area [21]. Various inorganic nano pigments have been used to enhance corrosion resistance of organic coatings. Nano particles such as Fe2O3, SiO2, and clay are common pigments in this regard [22-27]. It is suspected that nano Fe2O3 particles provide superior anti-corrosion properties than other inorganic pigments [28]. Furthermore, Fe2O3 minerals are abundant and have reasonably low costs.
