Manganese and iron phosphate conversion coatings' effect on low carbon steel scale's microstructure, corrosion resistance and friction performance when treated at high temperatures

Abstract

Scale formation is a natural result of heating steel to temperatures required for the hot forming process. While this scale formation has several beneficial properties, it also greatly reduces production yields making scale-reducing treatments enticing for manufactures. Steel samples were heated in an inert atmosphere to 860 °C and 1000 °C and sprayed with iron and manganese phosphate conversion coatings while hot. Steel scale began growing immediately upon the removal of samples from the furnace and treatments were then applied to this forming layer. Characterization of this modified scale layer was done using LOM, SEM, EDS, and XRD. The corrosion and mechanical properties of the treated layers were compared to untreated samples using neutral salt spray (NSS), twist compression testing (TCT), reciprocating wear testing (RCP), and microhardness measurements. The treated samples showed increase corrosion resistance and a decrease in friction. EDS analysis confirmed the treatments changed the scale's composition and structure. The treated samples showed less porosity than samples sprayed with just water. Proper application of these treatments during the hot rolling process has the potential to reduce coil field corrosion and increase steel yields.