Study of nicotinamide and thiourea on acid corrosion of mild steel by DC polarisation methods

Mild steel (C=0.11%) electrode was exposed to stagnant 0.1 N HCl containing 0.1% and 1% concentrations of Nicotinamide (NIC) and Thiourea. (TU) and their mixtures. Effect on acid corrosion by these additives was studied by DC polarisation methods. Both low (+/- 10 mV) and high cathodic and anodic polarisation studies were made to obtain polarisation resistance and corrosion current densities respectively. NIC decreased corrosion when concentration was increased from 0.1% to 1% but not TU. Instead, TU at 1%, increases corrosion rate. Addition of 0.1% NIC in 1% TU did not decrease undesired ed corrosion accelerating effect of 1% TU. However, increase in concentration of NIC from 0.1% to 1% has brought down the higher rate of corrosion observed in 1% TU alone or when 0.1% NIC was added in 1% TU. Combination of 0.1% NIC and 0.1% TU was better than 0.1% NIC alone. Mixture of 1% NIC and 0.1% TU was best in inhibiting corrosion mild steel in 0.1 N HCl.