Weight loss and thermometric methods have been used to study the corrosion inhibition of mild steel in acidic solution (HCl and H 2 SO 4 ) by Schiff's bases viz. N-(4-N,N-dimethylaminobenzal)-p-anisidine (SB 1 ), N-(4-N,N-dimethylaminobenzal)-p-toluidine (SB 2 ) and N-(4-N,N-dimethylaminobenzal)-2,4-dinitroaniline (SB 3 ). The efficiencies have been compared with those of parent amines from which Schiff's bases have been derived. Results of inhibition efficiencies observed from these two methods are in good agreement and have been found to be dependent on the concentrations of inhibitors as well as those of acids. Inhibition efficiency of all inhibitors increases with increasing concentration of inhibitors. Efficiency also increases with increasing concentration of acids. Inhibition efficiency is more in case of HCl rather than in H 2 SO 4 . Inhibition efficiency was found maximum up to 95.55% for mild steel in HCl solution. Inhibition efficiencies of synthesised Schiff's bases have been found much more than their parent amines. It was observed that inhibition efficiency of all amines increases with increasing concentration of amines but decreases with increasing concentration of HCl and H 2 SO 4 .

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Weight loss and thermometric methods have been used to study the corrosion inhibition of aluminium in HNO 3 by Schiff base N-(4-N,N-dimethylaminobenzal)-p-anisidine with and without additive (KNO 3). The present study reveals that aluminium in HNO 3 has been more efficiently inhibited by Schiff base in the presence of additive (KNO 3) than Schiff base alone, this enhanced inhibition efficiency in the presence of KNO 3 are due to the synergistic effect. Inhibition efficiency was found maximum (85.69%) for aluminium in 2N HNO 3 by N-(4-N,N-dimethylaminobenzal)-p-anisidine at an inhibitor concentration of 0.7% in presence of additive (KNO 3). . Inhibitor adsorbs on the metallic surface and forms a monolayer. Results obtained in both the methods show a good agreement and indicate the dependence of inhibition efficiencies on the concentration of Schiff base, additive (KNO 3) and also on the concentration of HNO 3 solution. The results show the increasing trends of inhibition efficiency with the increasing concentration of inhibitor, additive and also on the increasing concentration of HNO 3 .