Rice Hull Ash Nanosilica: Characterization and Its Potential as Silicate Coating for Carbon Steel

Abstract

Corrosion of steel structures is one of the main causes of destruction and loss of materials due to the damages it can bring to operating, storage, and structural equipment. Anti-corrosion inhibitors available in the market frequently contain chromium and lead, which are hazardous to human health and the environment. This study focused on the synthesis of nanosilica from the agro-industrial byproduct rice hull ash (RHA) and examined its potential as a corrosion barrier. Steel specimens were prepared in the form of 4mm thick disks cut from 16mm steel bars. RHA nanosilica was synthesized via acid precipitation method and characterized using x-ray diffraction (XRD), dynamic light scattering (DLS), atomic force microscopy (AFM), and Fourier Transform Infrared (FTIR) Spectroscopy. After characterization, 2.5%w/v RHA nanosilica was used to formulate sodium silicate as a coating for the steel specimens. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20Hz to 20MHz frequency range. The generated Nyquist plot showed that the specimen coated with sodium silicate with RHA nanosilica has a much larger diameter than red oxide indicating better protection against corrosion. The generated Bode plots confirmed this result as it showed that the specimens coated with sodium silicate with RHA nanosilica had higher impedances than those coated with red oxide, especially in the low-frequency regions.