Cr系白口铸铁的相间腐蚀机理及其电化学行为

应用定向凝固技术制备了Ｃｒ系白口铸铁，采用萃取法制备碳化物试样，用失重法测得腐蚀速率，并通过电化学法探讨Ｃｒ系白口铸铁在腐蚀介质中的相间腐蚀机理，结果表明：⑴Ｃｒ系白口铸铁在腐蚀介质中存在严重的相间腐蚀，相间腐蚀失重率占合金总体育馆２失重率的一半以上；⑵碳化物的电化学行为不同于合金和基体，一直处于自钝化状态，Ｍ７Ｃ３型碳化物比Ｍ３Ｃ型更耐蚀，更稳定；⑶碳化物与基体两相间的腐蚀电位差是相间腐蚀的驱动

MECHANISM AND ELECTROCHEMICAL BEHAVIOR OF INTER-PHASE CORROSION OF CHROMIUM WHITE CAST IRONS

Chromium white cast irons used for test have been prepared by the directional solidification technique and the extracting phase method was used for preparing carbide sample. The corrosion rates have been determined by the weightless and the inter-phase corrosion mechanism of chromium white cast irons in corrosion medium has been studied by the electrochemistry. The followed results are acquired. First, the inter-phase corrosion of chromium white cast irons is very serious in corrosion medium which corrosion weightless rate is more than half alloy corrosion weightless rate. Second, the electrochemical behavior of carbide is different from alloy and matrix, and is always in passive state. The corrosion resistance of M7C3 carbide is higher than M3C carbide. Third, the corrosion potential difference between carbide and matrix is the driving force of the inter-phase corrosion and in this corrosion process, carbide is protected but matrix is accelerated corrosion. Increasing the corrosion potential of the matrix not only reduces the inter-phase corrosion rate but also greatly raises corrosion resistance of white cast irons.