镍电极在硼砂-硼酸缓冲溶液中的钝化和点蚀

STUDY OF PASSIVATION AND PITTING CORROSION FOR Ni ELECTRODE IN BORAX-BORATE SOLUTION

近年来交流阻抗技术用于研究局部腐蚀,尤其在点蚀方面,引起了很大兴趣。Mansfeld等人和Oltra等人都提出了电极在点蚀时的等效电路.有关镍电极在Cl-存在时的点蚀研究有过许多报导,但是至今尚未见到用交流阻抗技术研究Ni电极的点蚀.本文用交流阻抗技术对Ni电极在Na2SO4硼砂-硼酸缓冲溶液（pH8.4）中的钝化行为和Cl-存在时的点蚀行为进行了研究,探讨了钝化和点蚀的规律和机理。

The passivation behavior and the pitting process at the fixed potentials for Ni electrode in Na_2SO_4-borax-borate buffer solution have been studied with alternatingcurrent(AC) impedance technique. For the passivation in the Cl^--free buffer solutionthe maximum of impedance moduli |Z| and the minimum of capacitances C_(dl) appearedat the potential of -0.2V (vs. Hg/HgO),because both the thickness of passive filmand the rate of anodic dissolution increased with rising potential. As the pitting wenton in the Cl^--containing buffer solutions at the fixed potentials, |Z| at low fre-quencies decreased and θ_(max) became smaller. Three typical cases, with the Cl^- concen-trations of 0. 1, 0.05, 0. 01 mol·L^(-1) and the fixed potentials of 0. 2, 0. 7, 0.7V,respectively, are discussed.