Thermally sprayable polyethylene coatings for marine environment

Application of organic coatings is one of the methods for protection of mild steel against corrosion. In the present work, low-density polyethylene (LDPE) has been used as binder for development of anticorrosive coating. Since non-polar characteristics of LDPE make its adhesion poor to most substrates, polar groups have been introduced in LDPE by grafting maleic acid (MAc) using reactive extrusion method. Grafted LDPE was characterized by chemical method, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), wide angle X-ray scattering (WAXS) and melt flow index (MFI). Grafted LDPE was pigmented with different pigments such as red iron oxide, micaceous iron oxide (MIO), titanium dioxide (TiO₂) and aluminium at three concentrations (i.e., 20, 30 and 40%). These compositions were applied on grit blasted mild steel specimen by flame spray technique. The coated specimens were evaluated for adhesion strength and resistance to corrosion in salt spray, humidity and seawater. Red iron oxide-based composition showed better adhesion and corrosion resistance compared to other compositions. Subsequently, corrosion resistance of red iron oxide-based compositions was studied by electrochemical impedance spectroscopy (EIS). The modified LDPE coating containing 30% red iron oxide showed higher resistance to corrosion compared to 20 and 40% red iron oxide-based compositions.