磷偏析对低碳钢孔蚀扩展的影响

    选择6种冶金因素各有特点的低碳钢,通过模拟“闭塞腐蚀电池”试验和室内挂片试验,结合金相组织、硫印、磷偏析和腐蚀形貌分析,研究磷偏析对孔蚀扩展的影响.结果表明,腐蚀形貌上呈现出凹凸状的平行腐蚀沟槽,这种平行腐蚀沟槽与磷偏析相关,而不是与沿轧制延伸的夹杂物(硫偏析)或平行的带状组织(碳偏析)相关.凹凸状的平行腐蚀沟槽形成原因是磷在溶液中离解为磷酸根离子,产生微溶的金属盐,在蚀坑的阳极活化区沉淀,从而抑制了阳极溶解. 

EFFECT OF PHOSPHORUS SEGREGATION ON PITTING PROPAGATION IN LOW-CARBON STEELS

    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 PO^3-₄ ion in pit as product of tiny dissolved phosphate, which precipitates on the activating area of anode so that suppress the anodic reaction.