Co-apatite phosphate compound: High-Performance corrosion inhibition in highly aggressive HCl solution (1.0 M and 5.0 M) and biological assessment

In this study, a novel inorganic Co-Apatite Phosphate substituted with cobalt ions (named CCP) of formula Co 2 Ca 6 (HPO 4 )(PO 4 ) 5 (OH) was synthesized and evaluated for its multifunctional properties, encompassing corrosion inhibition, as well as antibacterial and antifungal activities. The synthesis process was conducted following a green chemistry approach and the phosphate compound was thoroughly analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Electrochemical techniques were employed to investigate the corrosion prevention performance against carbon steel in two different hydrogen chloride acidic medium concentrations (5.0 M and 1.0 M HCl). The inhibitor demonstrates excellent performance in both mildly and highly acidic environments. In less corrosive environment of 1.0 M HCl, the inhibition efficiency is estimated to be 96.4 %, while under more corrosive 5.0 M HCl, the efficiency remains high at 90 %. In addition, biological assays revealed that the material exhibited notable antibacterial activity and antifungal effectiveness against both Gram-negative and Gram-positive. These results confirm the potentiality of CCP as a green multifunctional inhibitor effective in both harsh and microbially active environments (antimicrobial and antifungal).