Effect of Grain Size on the Corrosion Behavior of Fe-3wt.%Si-1wt.%Al Electrical Steels in Pure Water Saturated with CO2

Abstract

The corrosion behavior of two silicon steels with the same chemical composition but different grains sizes (i.e., average grain area of 115.6 and 4265.9 µm2) was investigated by metallographic microscope, gravimetric, electrochemical and surface analysis techniques. The gravimetric and electrochemical results showed that the corrosion rate increased with decreasing the grain size. The scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopyanalyses revealed formation of a more homogeneous and compact corrosion product layer on the coarse-grained steel compared to fine-grained material. The Volta potential analysis, carried out on both steels, revealed formation of micro-galvanic sites at the grain boundaries and triple junctions. The results indicated that the decrease in corrosion resistance in the fine-grained steel could be attributed to the higher density of grain boundaries (e.g., a higher number of active sites and defects) brought by the refinement. The higher density of active sites at grain boundaries promote the metal dissolution of the and decreased the stability of the corrosion product layerformed on the metal surface.

Synthesis and Characterization of Novel NiW–CeO2 Composite Coating with Enhanced Corrosion and Wear Resistance

“…The smaller grain size promotes the formation of more compact passive films with a lower amount of defects due to the increase in the active atoms number on the surface. This can decrease the adsorption of chloride ions on the surface and remarkably enhance the pitting corrosion and wear resistance of the coatings [40][41][42]. It was also noticed that the intensity of Ce (111), Ni (111), Ni (220), and Ni (311) increased with the increase in the annealing temperature.…”

Assessment of Foundry Chromite Sand Crushability under Thermal-Mechanical Loading

“…The parameter n quantifies the imperfections of the surface. For n = 1, CPE is a pure capacitor, and for n = −1, CPE is an inductor [6,15]. The data shows that Rp increased in the presence of Ti micro-inclusion in the metallic matrix from 231.41 to 325.74 Ω cm 2 , reflecting an improvement in corrosion resistance of around 30%.…”

“…The potentiodynamic polarization (PDP) experiments were carried out after 24 hours of exposure to the tested solution at OCP, with a sweep rate from -0.3 V to 0.3 V versus OCP, and a scan rate of 1 mV s -1 . The E% was calculated from the measured corrosion current densities (j corr ) values using the following equation [15]:…”

“…Rct and Qdl are the charge transfer resistance and the capacitance of the double layer, respectively. Due to the imperfection of the metal surface, the double-layer capacitance (Cdl) was simulated via a constant phase element (CPE) [6,15]. The impedance of CPE is described by the following equation:…”