Corrosion protection of mild steel in SO2 environment by nanocoating with filler

Abstract

SO2 is a very dangerous corrosive pollutant. This corrosive gas produces dangerous corroding effect with materials. It reacts with moist oxygen to form acids which generates corrosion problems with materials. It changes their physical, chemical and mechanical properties and tarnishes their appearance. Mild steel is a very important engineering metal and it is used for several appliances in day to day life. Mild steel is highly sensitive toward moist SO2. It develops corrosion cell on the surface of mild steel and undergoes with corrosion reaction. Metal exhibits galvanic corrosion, pitting corrosion, crevice corrosion, and stress corrosion. The concentration of SO2 gas is increasing day by day in the atmosphere due to industry, transport, road, housing, infrastructure development works and decomposition of living organisms. Its concentration was measured in summer, rainy and winter seasons in industrial areas of different cities and its corrosive effect studied on mild steel. It is observed that concentration of SO2 gas varies from season to season. Its concentration is more in winter than in summer and rainy. This result shows that mild steel corrodes more in winter seasons with respect of summer and rainy seasons. Nanocoating technique is used to check the corrosion of mild steel in SO2 environment. For this work, AlPO4 is applied as coating materials and DLC (diamond like carbon) as filler. Nanocoating work completed with nozzle sprays and chemical vapour deposition methods. The corrosion rate and corrosion current density of metal were calculated by gravimetric and potentiostatic polarization techniques. Surface coating phenomena and its stability studied with help of Arrhenius equation and Langmuir isotherm and thermodynamical parameters like activation energy, heat of adsorption, free energy, enthalpy and entropy.