Investigation of Pitting Defects on Two Phosphated Low Alloy Steel Rods

摘要

This study investigates the formation of pitting defects on two phosphated low alloy steel rods containing, respectively, 1.1 percent Si and 1 percent Cr. Test steels included a phosphated rod, an as-rolled rod, and a lab-melted ingot. An optical microscope (O M) or a scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) were employed to analyze the surface morphology and the cross-sectional microstructure of the individual stage during manufacturing process. The results indicated that the pitting defects came from a corrosion of the substrate adjacent to residual Si/Cr-containing iron oxide before phosphating. After phosphating, the small pits became large pits or large area corrosion zones visible as defects to the human eye.