Study of the inhibitory effect of tetracycline hydrochloride on mild steel in HCl, HNO3, H2SO4 and NaCl solutions

This study investigates the potential of tetracycline hydrochloride as a corrosion inhibitor for mild steel in various corrosive environments, including 1 M H₂SO₄, 1 M HCl, 1 M HNO₃, and 0.05 M NaCl. The inhibition efficiency of tetracycline hydrochloride was evaluated using electrochemical impedance spectroscopy (EIS), metallographic analysis with optical microscope, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and weight loss measurements. The results indicate a maximum inhibition efficiency of 74.10 % in the sample with 500 ppm of tetracycline hydrochloride in HCl, while efficiencies of 41.16 %, 59.76 %, and 72.58 % were observed for H₂SO₄ (500 ppm), HNO₃ (100 ppm), and NaCl (100 ppm), respectively. For the EIS analysis, the measurements were performed in a frequency range from 10 kHz to 0.01 Hz, with an amplitude of 0.01 V. This study suggests that tetracycline hydrochloride has promising potential as a corrosion inhibitor in various industries, offering a sustainable alternative for the reuse of expired medications.