Reviving expired pharmaceuticals using 2-[(butylamino)propan-2-yl]phosphinic acid for corrosion protection of carbon steel in 1.0 M HCl

This study primarily focuses on how the expired pharmaceutical 2-[(Butylamino)propan-2-yl]phosphinic acid (BAMPA), which contains both an amino and phosphinic acid group, can form a highly effective protective layer on the carbon steel surface using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) methods. Electrochemical experiments reveal that BAMPA adsorbs to carbon steel, producing a protective coating. At 500 ppm BAMPA, charge transfer resistance (R_ct) rose from 18.88 to 160.1 Ω cm², while double layer capacitance (C_dl) decreased, indicating a reduced surface area for corrosion. The inhibition efficiency reached 95.20% at 500 ppm BAMPA. Theoretical calculations of electronic properties, including E_HOMO (- 4.106 eV), E_LUMO (- 3.279 eV), and an energy gap of 0.827 eV, support BAMPA's high reactivity and potential for effective electron transfer. These findings confirm BAMPA's potential as a viable corrosion inhibitor.