Study of the corrosion resistance of high chromium white cast iron welds in the presence of NaOH (30% w/w)

Abstract

– In the mining industry, specifically in bauxite processing, adverse working conditions demand high mechanical and chemical resistance. For such conditions, the choice of potentially resistant materials, such as high chromium white cast iron (HCr-CWI), is necessary. However, presently, there is no effective recovery of equipment made with HCr-CWI, primarily due to the machining difficulties encountered during the repair process. An alternative recovery method is being developed by the Laboratory of Metallic Materials Characterization at UFPA – LCAM, using electric arc welding with two filler metals: the ER307L stainless steel wire andsa high Mn value wire. Within this context, this study aims to investigate the corrosion resistance of the welded joint obtained with these two filler metals. The base metal (HCr-CWI) was analysed as a reference, alongside the metals generated by the welded joints, ER307L and high Mn. The samples underwent tests involving optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical tests for corrosion potential, polarization, and impedance. It was observed that the samples exhibited a similar matrix-carbide structure but with different organization and volumes. However, the electrochemical behaviour in terms of corrosion potential, polarization, and impedance was similar, with very close resultant values: 50V; 3.53 μA; 0.18 kOhms, respectively. This was supported by the corrosion rate of 0.4mmpy and explained by calculations of Cr and Ni volume, which showed inverse concentration magnitudes among the samples.