Influence of anions on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions in the presence of p-tolyl thiourea

The influence of anions such as chloride and sulphate on the inhibition of corrosion of mild steel by p-tolyl thiourea (PTTU) in 1N HCl and 1N H sub 2 SO sub 4 has been studied using weight loss and gasometric measurements, galvanostatic polarisation studies and ac impedance measurements. The compound is found to be less inhibitive in 1N HCl than in 1N H sub 2 SO sub 4 . The influence of p-tolyl thiourea on the extent of hydrogen permeated through mild steel in acidic solutions has been studied using electro-permeation technique. The compound is found to enhance the permeation of hydrogen through mild steel in both the acids. The adsorption of p-tolyl thiourea on the mild steel surface from both the acids obeys Temkin's adsorption isotherm. The increase of charge transfer resistance (R sub t ) and decrease in double layer capacitance (C sub dl ) values of the metal electrode in the presence of the test compound (PTTU) show the adsorption of the compound on the metal surface.