Corrosion protection of stainless steel in CO₂ environment by nanocoating of zinc phosphate with DLC filler

CO₂ gas produces corrosive effect with stainless steel. It reacts with moisture to give carbonic acid. This acid interacts with stainless steel to develop corrosion cell. Metal corrodes and it exhibits different forms of corrosion like galvanic, pitting, crevice, stress, intergranular, embrittlment etc. Stainless steel is a very important engineering material. It is used in various scientific and engineering equipments. It loses its metallic properties due to corrosive CO₂. The concentration of CO₂ is increasing in atmosphere day by day. The major causes of this is industrialization, burning of coal, petroleum refinery, thermal power plant, urbanization, decomposition of agricultural wastes, human wastes and animal wastes. The corrosion phenomenon was studied into summer season, rainy season and winter season. Zinc phosphate was selected as nanocoating material and this nanocoating was covered by DLC (diamond like carbon). Such type of coating was completed by nozzle spray. The corrosion rate was determined in different season by weight loss method and potentiostatic polarization technique. The experimental results show that stainless steel corrodes more in winter season with respect of summer and rainy season. The coating of zinc phosphate minimized the corrosion rate but DLC coating on the surface of zinc phosphate produced good anticorrosive effect in these seasons. The surface coverage area indicated that coating materials zinc phosphate and DLC were highly effective in CO₂ environment. Thermodynamical results of activation energy, heat of adsorption and free energy showed that these coating materials have good binding forces with base metal.