Enhancing steel corrosion resistance in 1.0 M HCl medium through the synthesized and characterized mixed pyrophosphates BMnP2O7 (B = Ni, Co, and Cd)

Abstract

In this study, we synthesized three diphosphate materials NiMnP2O7, CoMnP2O7, and CdMnP2O7 intended for use as corrosion inhibitors for carbon steel. The crystallinity of the obtained compounds was analyzed using X-ray diffraction (XRD), and a vibrational analysis was carried out by infrared (IR) and Raman (Ra). The corrosion inhibition properties of steel with these materials in 1.0 M HCl solution were investigated using three important techniques. The electrochemical parameters were obtained via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP) and the surface of the substrate was analyzed, using the scanning electron microscopy (SEM). Our findings indicate that the optimal concentration for NiMnP2O7, CoMnP2O7, and CdMnP2O7 was 10−3 mol/L, with inhibition efficiencies reaching to 87.5 %, 91.04 %, and 92.22 %, respectively. These phosphates also act as a mixed-type inhibitors, imparting high resistance to corrosion, and their inhibition efficiency (η%) increased with the augmentation of the inhibitor concentration. The scanning electron microcopy (SEM) images revealed that the inhibitors form a protective layer against acid attack, preventing carbon steel from being destroyed.