Corrosion of a Spark Plasma Sintered Fe-Cr-Mo-B-C Alloy in Hydrochloric Acid

This research studied the electrochemical corrosion behavior in 1 M hydrochloric acid of a Fe-Cr-Mo-B-C alloy fabricated using spark plasma sintering of an amorphous alloy starting powder. The corrosion performance was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization tests and was benchmarked with conventional materials: 316L stainless steel and 1080 carbon steel. The corrosion reaction products on the surface were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive spectroscopy. The specimen sintered at 800 °C had approximately 94% densification, whereas the specimen sintered at 900 °C exhibited greater densification of approximately 98%. The sintered specimens consisted of nanocrystalline (Fe,Cr)23C6 and (Cr,Fe)2B particles embedded in a body-centered-cubic Fe-based matrix. These sintered specimens exhibited better corrosion resistance than conventional alloys. When the density of the sintered alloy decreased from 98 to 94%, resistance to chloride attack was increased because of the formation of a thicker and more uniform surface product as well as a chromium-containing oxide layer.