Experimental and Theoretical Study of Pinostrobin as Copper Corrosion Inhibitor at 1 M H2SO4 Medium

Abstract

The effect of variations in concentration and temperature on the efficiency of pinostrobin corrosion inhibition of copper in 1M H2SO4 was studied using an experimental and theoretical approach. Pinostrobin was isolated from the Boesenbergia rotunda L rhizome and was tested for corrosion inhibition of copper in acidic medium. Variations in the concentration of 300 ppm, 400 ppm, and 500 ppm and temperature (308 K, 318 K, and 328 K) were carried out in the weight loss method of corrosion inhibition test. Pinostrobin crystals were isolated with a yield of 57.65 %, a melting point of 98.5 °C and with a purity of 100 %. The optimum corrosion inhibition efficiency of pinostrobin is 65.71 % at a concentration of 500 ppm and a temperature of 328 K. The activation energy value of Ea < 80 kJ.mol−1 indicates the adsorption of pinostrobin on copper surfaces is physical and spontaneously ΔG°ads < -20 kJ.mol−1. The effect of substituent on the efficiency of corrosion inhibition from pinostrobin was studied using density functional theory. The addition of NH2 increased the efficiency of corrosion inhibition to 73.07 %, whereas the addition of NO2 substituents decreased the efficiency of inhibition to 60.97 %. Experimental and theoretical studies have a good correlation in explaining the efficiency of corrosion inhibition from pinostrobin.