Piperidines as corrosion inhibitors for iron in hydrochloric acid

The objective of this work is to provide additional insight on the influence of substituents on heterocyclic piperidine as acid corrosion inhibitors for iron. This series include piperidine and six derivatives. The inhibiting properties of piperidine and these derivatives were investigated in 1 M HCl by potentiodynamic polarization (dc) and electrochemical impedance spectroscopy measurements, and inhibition was found to increases as 26dp<35dp<2mp<3mp<4bp<4mp. Polarization curves suggest that they can all be considered as mixed-type inhibitors. An attempt to correlate electronic properties of the compounds with their experimental efficiencies using molecular orbital calculation methods did not show any clear-cut relationship.