Power of hydrogen (pH) effects on physical and mechanical properties of steel coated in rice husk-based smart corrosion inhibitors of mesoporous silica

This study was aimed at determining the effects of the power of Hydrogen (pH) on physical and mechanical properties of steel coated in rice husk-based smart corrosion inhibitors of mesoporous silica, i.e. morphology, chemical compositions, corrosion rates, and corrosion resistance. The morphological and chemical composition testing employed Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDS), the corrosion rate testing employed the weight-loss method, and the corrosion resistance testing employed Electrochemical Impedance Spectroscopy (EIS). The sample of this research was AISI 1020 steel with a mesoporous silica concentration of 0.5%. For 15 days, it was immersed in 3.5% of NaCl with four pH variations, i.e. 3, 7, 11, and 13. The results of the SEM analysis show the higher the pH, the smaller the morphological changes, i.e. clusters, holes, and cracks. The results of the EDS analysis show the greater the pH, the lower the composition of the corrosion elements, i.e. 86.70% (76,03% of Fe and 10.67% of O) at a pH of 3 and 85.57% (72,47% of Fe and 13.1% of O) at a pH of 11. The results of the corrosion rate calculation show the stronger pH’s led to the slower corrosion rates, i.e. 20.284 ×10−5 mm/yr at a pH of 3 and 5.216×10−5 mm/yr at a pH of 13. The results of the EIS analysis show the corrosion resistance was in line with the degree of the pH. This is indicated by the greater value of the semicircle diameter of the formed Nyquist plot.