AZ31镁合金阳极氧化膜在3.5%NaCl溶液中不同浸泡时间的腐蚀机制

Corrosion Mechanism of Anodic Oxidation Film on AZ31 Magnesium Alloy in Sodium Chloride Solution

为了进一步弄清AZ31镁合金阳极氧化膜在NaCl溶液中的腐蚀机制,采用极化曲线、电容测量技术,基于半导体电化学方法研究了其在3.5%NaCl溶液中耐蚀性能与其半导体特性的关系,得到不同浸泡时间下的载流子浓度以及平带电位。结果表明:镁合金阳极氧化膜为N型半导体,随浸泡时间的增加,载流子浓度呈上升趋势,由浸泡10 min时的1.83×1018cm-3增大到96 h时8.60×1020cm-3,平带电位为-1.69～-1.52V,低于镁合金(-1.44～-1.57 V),在浸泡时间为1 h时膜的平带电位最负,耐蚀性最好;镁合金阳极氧化膜的腐蚀失效过程会经过自我修复期-点蚀诱导期-点蚀期-快速腐蚀期4个阶段。

A semiconductor electrochemical method was adopted to measure the polarization curve and capacity of anodic oxidation film on AZ31 Mg alloy in 3.5%NaCl solution so as to reveal the correlation between the corrosion resistance and semiconductor characteristics of the film.The carrier density and flat-band potential of the anodic oxidation film at different immersion time were determined.Results showed that the anodic oxidation film formed on Mg alloy surface was an N-type semiconductor,and its carrier density tended to rise with extending immersion time(it increased from 1.83×1018 cm-3 at 10 min of immersion to 8.60×1020 cm-3 at 96 h of immersion).Besides,the anodic oxidation film had a flat-band potential of-1.69～-1.52 V(lower than that of Mg alloy(-1.44～-1.57 V)),and the anodic oxidation film obtained at an immersion time of 1 h had the lowest flat-band potential and possessed the best corrosion resistance.Moreover,the failure process of the anodic oxidation film could be divided into four stages,including self-repair period,induction period of pitting corrosion,pitting corrosion period and quick corrosion period.