Influence of Cassava Cyanided on the Corrosion Behaviour of Cyanided Ductile Cast Iron in Sodium Chloride (NaCl) and Sulphuric Acid (H2SO4)

Abstract

The study investigated the corrosion behavior of produced cyanided ductile cast iron (CCDCI) in aqueous salt solutions of 3.5 wt% NaCl and acidic media of 0.1\xa0M, 0.3\xa0M, and 0.5\xa0M H 2 SO 4 respectively. Microstructural characterization of the cyanide ductile iron was carried out using scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) to reveal the phase formation owing to the cassava cyanide heat-treatment procedure. The potentiodynamic polarization tests were carried out using VersaSTAT potentiostat at room temperature. The X-ray diffraction analysis of the cyanided samples revealed cases containing predominantly epsilon nitride (Fe 3 N) and gamma prime nitride (Fe 4 N), Fe 3 C, and martensitic phase on the surface of the treated samples, while the cores revealed phases of cementite (Fe 3 C), silicon carbide (SiC), iron–silicon carbon (FeSiC) and iron–silicon (FeSi) forming the ferrite and pearlitic phases within the matrix. Also, the corrosion resistance of treated cyanided samples in 3.5 wt% NaCl solution significantly increased with respect to variances in temperature while the samples in H 2 SO 4 solution show divergence in corrosion resistance which varies with respect to the increase in the morality of the acidic media. Besides, the polarization measurements showed that the E corr and I corr of the cyanided ductile cast iron samples increase with increasing H 2 SO 4 concentration.