Electrochemical and thermodynamic studies to evaluate the inhibition effect of synthesized piperidine derivatives on the corrosion of mild steel in acidic medium

The inhibition ability of three newly synthesized piperidine sulphonamides toward the mild steel (MS) corrosion was investigated using mass loss and electrochemical techniques. The adsorption of all the piperidine sulphonamides on MS complies with the Langmuir isotherm model in all studied temperatures. Associated activation and adsorption thermodynamic parameters were computed and discussed. The polarization results indicated that all the studied inhibitors act as mixed type of corrosion inhibitors. The protective layer of organic compounds on MS surface was confirmed by scanning electron microscopy (SEM). The values of free energy of adsorption (Delta G (ads)) revealed that the inhibitors adsorbed on the MS surface via both chemisorption and physisorption mechanisms. The relationship between inhibition efficiency and molecular structures of inhibitors was discussed using quantum chemical parameters. The inhibition efficiencies obtained from mass loss and electrochemical measurements were in good agreement.