4种不同金相组织的仿古铸铁在土壤中局部腐蚀行为的差异

为了加强铸铁文物的保护，采用动电位扫描极化、模拟闭塞电池、交流阻抗等电化学方法，以及光镜、扫描电镜等显微组织分析手段，研究了4种仿古铸铁在模拟土壤介质（0．06mol／L NaCl＋0．03mol／L Na2SO4＋0．01mol／L NaHCO3溶液）中的局部腐蚀行为，详细探讨了组织差异对仿古铸铁局部腐蚀的影响。结果表明：珠光体灰口铸铁的自腐蚀电位负移最为明显，在模拟土壤条件中裂纹和腐蚀孔洞相对其它几种仿古铸铁较多。在闭塞电池中，仿古铸铁的pH值下降，Cl^-和SO4^2-增加，仿古铸铁耐蚀性依次递减的顺序为白口铸铁、麻口铸铁、珠光体＋铁素体灰口铸铁、珠光体灰口铸铁。

Difference of Local Corrosion Behaviors of Archaeological Cast Irons with Four Different Microstructures in SOil

In order to reinforce the protection of as-cast antiques, the local corrosion behaviors of archaeological cast iron with four different microstructures in soil media (0.06 mol/L NaCl+0.03 mol/L Na2SO4+0.01 mol/L NaHCO3 aqueous solution) were investigated by polarization curve, simulated occluded cell (O.C.), electrochemical impedance spectroscopy (EIS) technique, optical microscope (OM) and scanning electron microscope (SEM). The influence of different microstructures on the local corrosion was studied in detail by comparing the chemical, electrochemical behaviors and the corrosion morphology of four types of cast iron. The results show that pearlite gray cast iron has the lowest open circuit potential among the four types of cast iron; and the crack and cavities are more than those of other cast irons corroded in the soil media. Within the occluded cell, autocatalytic effect causes the decrease of pH value and the enrichment of Cl-and SO42-. The corrosion resistance of the archaeological cast irons decreases in the order of white cast iron, mottled cast iron, pearlite-ferrite gray iron, and parlitic gray iron.