Inhibition efficiency of expired metformin drugs as a corrosion inhibitor in boiler pipes.

Research has been carried out on the inhibition efficiency of expired metformin drugs as a corrosion inhibitor for boiler pipes. Metformin is highly soluble in water, contains five nitrogen atoms, which provides adsorption in the formation of thin films on metal substrates, and has considerable anti-corrosion behaviour. This study aimed to determine the efficiency of Metformin expired drugs to inhibit corrosion and optimize the use of Metformin expired drugs. The research was conducted by characterizing the steel pipe sample using optical emission spectroscopy (OES), characterizing the expired Metformin drug sample using Fourier transform infrared spectroscopy (FTIR), measuring the corrosion rate and inhibition efficiency using the weight-loss method, and surface morphology analysis using a scanning electron microscope (SEM). The results of the characterization of the steel pipe sample showed that the sample was composed of Fe, C, Si, Mn, P, S, Cr, Mo, Ni, Al, Co, Cu, Nb, Ti, V, W, and Pb elements. The characterization of expired drug samples showed stretching of the amine group at wavelengths 3369.5 cm-1 and 3295 cm-1, proving that Metformin was present in the expired drug. The results of the weight loss test showed that expired Metformin was able to inhibit corrosion with its optimal condition being at temperature 70oC with 25 ppm inhibitor, and the inhibition efficiency reached 73.54%. At temperature 50oC with 50 ppm inhibitor, the inhibition efficiency reached 84.81% in the corrosive medium NaCl. 3%. The SEM micrographs show the surface of the steel that does not use inhibitor looks damaged and has holes, while the surface of the steel that uses inhibitor looks smoother. [ABSTRACT FROM AUTHOR]