EFFECT OF PHOSPHORUS SEGREGATION ON PITTING PROPAGATION IN LOW-CARBON STEELS
磷偏析对低碳钢孔蚀扩展的影响

Six low-carbon steels with different metallurgical feature were selected.The effect of phosphorus segregation on pitting propagation was studied by means of OCC simulation test and indoor exposure test,as well as examinations of microstructure,sulfur segregation, phosphorus segregation and corrosion appearance.The results showed that there were concave-convex shape corrosion grooves on the corroded surface,which was related with phosphorus segregation,not the rolling sulfur inclusions(sulfur segregation)or zonal microstructure(carbon segregation).The tests indicate that the reason of forming concave-convex shape corrosion grooves on the corroded surface is due to the formation of PO3-4 ion in pit as product of tiny dissolved phosphate, which precipitates on the activating area of anode so that suppress the anodic reaction.