Corrosion and corrosion protection of mild steel in SO environment

SO 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 SO . It develops corrosion cell on the surface of mild steel 2
and undergoes with corrosion reaction. Metal exhibits galvanic corrosion, pitting
corrosion, crevice corrosion, and stress corrosion. The concentration of SO gas is 2
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 SO gas varies from season to season. Its concentration is more in winter 2
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 SO environment. For this work, AlPO is applied as 2 4
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.