Augmentation of Corrosion Inhibition Property of Thiourea by Aliphatic Amines in Presence of Aggressive Cl- ions and Acidic SO2 Environment

With the growth of industrialization and modernization, it has now become essential for any country to construct and develop the basic infrastructure like highways, high speed rails, metro trains, bridges, schools, colleges, hospitals, strong air vehicle network etc. Development of these basic requisites has created a strong demand for production of steel. And we are doing so. We are now 4th largest steel producer in world. But production of steel and its products is only one step towards a sustained growth. We are facing strong challenges in maintaining the quality of steel products. Atmospheric corrosion of almost all parts of these structural elements can cause serious losses to lives, a great loss of money and times as well. Atmospheric corrosion can aggressively accelerate the rate of degradation of steel during their manufacturing, processing, storage and transportation. In these cases, traditional methods to prevent corrosion are not suitable which provide scope of vapour phase corrosion inhibitors in industries, defense and daily life. Corrosion inhibition property of Thiourea is tested with aliphatic amines i,e. 1,3-Diaminopropane, N,N,N,N-Tetramethylethylenediamine and Ethylamine for mild steel in different aggressive atmospheric conditions of chloride ions and sulphurdioxide by Vapour pressure determination test, Weight loss test, Salt spray test and Sulphur dioxide test at 50°C. It is found that percentage corrosion inhibition efficiency of combinations are in order of Thiourea+N,N,N,N-Tetramethylethylenediamine > Thiourea+Ethylamine > Thiourea+1,3-Diaminopropane. Chloride ions affect the barrier layer of corrosion inhibitor on surface of mild steel coupon and produce porosity on mild steel surface. Mechanism of action of corrosion inhibitors and effect of aggressive corrodent on the surface of mild steel are supported by morphology of mild steel studied by Metallurgical research microcopy and Scanning electron microcopy. Results of scanning electron microscopy provide the evidence of crevice corrosion, formation of barrier layer of vapours of vapour phase corrosion inhibitors and penetration of that barrier layer by chloride ions on mild steel surface. It is found that percentage corrosion inhibition efficiency of Thiourea + N,N,N,N-Tetramethylethylenediamine is very high (80.98%) in weight loss test but become little bit low in NaCl and sulphurdioxide environments by aggressive action of chloride and sulphate ions respectively.