铬系白口铸铁相间腐蚀机理的探讨

为了探讨铬系白口铸铁在腐蚀介质中的相间腐蚀机理，对试验合金应用定向凝固技术，采用提取相表面富集法制备了碳化物试样；依据电偶腐蚀原理，建立了亚共晶铬系白口铸铁相间腐蚀原电池模型；测定了试验合金组成物偶接前、后的腐蚀速度。试验结果表明：（1）亚共晶铬系白口铸铁相间腐蚀可分为主、次相同腐蚀原电池、主相间腐蚀速度是次相间腐蚀速度的2倍左右；(2) 随铬碳比的增加，试验合金组成组的腐蚀速度均显著下降，但共晶基体的腐蚀速度仍然是初生基体腐蚀速度的2倍左右；（3）碳化物与基体两相间的腐蚀电位差是相间腐蚀的驱动力，在此腐蚀过程中，高电位的碳化物被保护，低电位的基体被加速腐蚀，提高基体的腐蚀电位，不仅可以降低相同腐蚀速度，而且可以大幅度提高铬系白口铸铁的耐蚀性。

Mechanism of Inter-Phase Corrosion of Chromium White Cast Irons

The inter-phase corrosion mechanism of hypo-eutectic chromium white cast irons is divided into the primary and secondary original cells according to the couple corrosion principles. The specimens are prepared by the unidirectional solidification technique and the drawing phase surface collection method. The primary cell corrosion speed is about twice as fast as that of the secondary cell. The corrosion speed of the constituents of alloys falls remarkably with increasing of the chromium-to-carbon ratio. For the eutectic matrix the speed is also about twice as fast as that of the primary matrix. Morever, the corrosion potential difference between carbide and matrix is the driving force of the inter-phase corrosion. Such that, the carbide was protected while the corrosion of the matrix is accelerated. Increasing the corrosion potential of the matrix not only reduces the inter-phase corrosion speed but also raises the corrosion resistance of white cast iron.