Amino acid Schiff bases as efficient corrosion inhibitor for mild steel in aqueous H2SO4: a comparative study

— Corrosion inhibitory performance of two Schiff bases prepared through condensation of two different amino acids, glycine and tyrosine with a common aldehyde, citronellal (designated as GCSB and TCSB, respectively) are compared by taking mild steel as test metal and aqueous H 2 SO 4 as the corrosive environment. Inhibition efficiencies as obtained through potentiodynamic polarization and electrochemical impedance spectroscopic methods establish TCSB as a superior corrosion inhibitor with 74 to 88 percentage of inhibition efficiency. Better corrosion mitigatory prowess of TCSB is explained in terms of various intrinsic molecular parameters, like the energy of frontier molecular orbitals (HOMO and LUMO), global hardness, softness, electrophilicity index, and others. It is revealed that two directional electron transfer, inhibitor to metal and retro-transfer, is responsible for the interaction of the Schiff bases with the metal surface. From electron distribution at HOMO and LUMO levels, atoms or functional groups present in the Schiff bases which initiate the molecular interaction with metal surface are ascertained.