Thiazole derivatives as corrosion inhibitors for C-steel in sulphuric acid solution

5-phenylazo-2-thioxo-thiazolidin-4-one and four of its derivatives have been investigated as corrosion inhibitors for C-steel in 1 M sulphuric acid solution using weight-loss and galvanostatic polarization techniques. The efficiency of the inhibitors increases with increase in inhibitor concentration but decreases with a rise in temperature. The conjoint effect of the thiazole derivatives and KBr, KSCN and KI has also been studied. The apparent activation energy (Ea*) and other thermodynamic parameters (ΔS*, ΔH* and ΔG*ads) for the corrosion process have also been calculated. The galvanostatic polarization data indicated that, the inhibitors were of mixed-type, but the cathode is more polarized than the anode. The slopes of the cathodic and anodic Tafel lines ( c and a) are approximately constant and independent of the inhibitor concentration. The adsorption of these compounds on C-steel surface has been found to obey the Temkin's adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors.