Inhibition Effect of Phthalocyaninatocopper(II) and 4- Tetranitro(phthalocyaninato)copper(II) Inhibitors for Protection of Aluminium in Acidic Media

摘要

The inhibition effect of phthalocyaninatocopper(II) (CuPc) and 4-tetranitro(phthalocyaninato)copper(II)(TNCuPc) on aluminium in 1 mol/L HCl was investigated by electrochemical techniques. The CuPc andTNCuPc inhibitors were synthesized and confirmed by using X-ray diffraction (XRD), Fourier transforminfrared (FTIR), simultaneous thermal analysis (STA, thermogravimetric analysis (TGA)/differentialscanning calorimetry (DSC)) and ultraviolet-visible spectroscopy (UV-vis). The XRD, UV-vis and FTIRanalyses showed successful formation of CuPc and TNCuPc inhibitors. The thermal stability of CuPcincreased upon the introduction of NO2 group in the peripheral position as indicative of the formation ofTNCuPc. The potentiodynamic polarization (PDP) curves of aluminium in the corrosive environment ofHCl in the presence and absence of CuPc and TNCuPc compounds demonstrated that both cathodic andanodic processes of Al corrosion were suppressed. The Nyquist plots of electrochemical impedancespectroscopy (EIS) expressed mainly as a capacitive loop with different concentrations of CuPc andTNCuPc. The inhibition efficiency of these inhibitors increased with increase in inhibitor concentration,and their inhibition efficiencies in the same concentration decreased in the order of CuPc > TNCuPcaccording to PDP and EIS results due to a steric hindrance.