在模拟填包料环境的硫酸钙-氢氧化镁饱和溶液中,在AZ41镁合金牺牲阳极直流放电的同时引入交流电干扰。试验发现,引入交流电干扰时采用不同形状的辅助电极,电场分布情况不同,放电试验后镁阳极形貌明显不同。镁阳极工作电位随着交流电干扰的增强而明显正移,有时甚至可能正于铁的开路电位,出现所谓的“极性逆转”现象。从硫酸钠+铁氰化钾+亚铁氰化钾溶液中测试的极化曲线来看,镁阳极上的腐蚀产物具有n-型半导体的导电特征。阳极电流效率随交流电流密度的逐步增大而明显下降。XRD分析表明,有交流电干扰时镁阳极腐蚀产物仍然只有Mg(OH)_2,这与单纯直流放电时的结果一样。
AC interference of various amplitudes was intentionally introduced during the standard current efficiency measurements for AZ41 magnesium sacrificial anode in a saturated calcium sulphate-magnesium hydroxide solution, to simulated the long-term environment around magnesium anodes installed in the backfill. Different forms of ac auxiliary electrodes led to different current distributions on the anode surface and thus resulted in different morphology after the anode was subject to galvanostatic dissolution. Under the influence of ac interference, working potential of the anode obviously shifted towards noble and even became nobler than the open potential of iron at greater ac density. Polarization curves obtained in a Na2SO4+K3[Fe(CN)6]+K4[Fe(CN)6] solution indicated that corrosion product film on the anode had the character of n-type semiconductor. The current efficiency of the anode significantly dropped with the increasing ac density. XRD analysis revealed that magnesium hydroxide was still the unique corrosion product in the simultaneous presence of dc and ac currents.
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