Cluster type molecule as novel corrosion inhibitor for steel in HCl solution

The MOF [Ag (qox) (4-hb)] 1, was obtained at room temperature by the reaction of AgNO3, quinoxaline (qox) and 4-hydroxy benzoate (4-hb). A cluster molecule containing two silver atoms, two qox and two 4-hb ligands is considered the basic building block of the structure of 1. 3D-network structure is created via H-bonds and pi-pi stacking. The MOF 1 was tested as corrosion inhibitor for carbon steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance techniques (EIS). The polarization measurements indicated that the MOF 1 is of mixed type. The adsorption of MOF 1 obeyed Langmuir adsorption isotherm. The inhibition efficiency increased with increase in MOF 1 concentration but decreased with increase in temperature. The activation and thermodynamic parameters were calculated and discussed. Mechanism of inhibition is explained on the basis of molecular structure of the inhibitor.