原位阻抗谱研究β相对镁-铝合金初期大气腐蚀行为的作用

Effect of β Phase on the Initial Atmospheric Corrosion Behaviour of the Magnesium-Aluminum Alloys by in-situ Electrochemical Impendence Spectra

采用原位电化学阻抗(EIS)技术研究了薄液膜条件下β相对镁铝合金初期腐蚀行为的影响。结果表明由NaCl诱发的镁合金初期大气腐蚀,β相起到了关键作用。在早期的10 h内,β相体积分数较多的镁合金对应阻抗谱的电荷转移电阻比较大,表明其腐蚀速率较慢,这是由于镁合金中β相相对耐蚀。但在高浓度Cl^-作用下,随暴露时间的延长,一旦突破合金表面β相的阻碍后电荷转移电阻明显下降,腐蚀速率加快。β相体积分数较少的镁合金随着暴露时间的延长,腐蚀产物膜的保护性明显优于β相体积分数较多的镁合金,这有助于减缓β相体积分数较少的镁合金基体在暴露后期的腐蚀速率。

The in-situ electrochemical impedance spectrum measurements were conducted to investigate the early stage of the atmospheric corrosion behavior of the magnesium alloys with different volume fractions ofβphase.The results indicated thatβphase played a key role in the course of atmospheric corrosion of the magnesium alloys that was induced by NaCl particles centralized in the early time period. During the early ten hours the magnesium alloys with high volume fractionβphase had a bigger charge-transfer resistance,showing a better corrosion resistance.This phenomenon could be attributed to the better corrosion resistance ofβphase.However,a faster corrosion occurred for the magnesium alloys with high volume fractionβafter ten hours when theβphases were broken and the charge-transfer resistance dropped dramatically due to the high concentration of Cl^-.As the exposure time prolonged,the protective function of the corrosion product films in Mg-3Al alloy was significantly better than those in the other two alloys as they helped slow down the corrosion rate of magnesium alloys with less volume fractionβphase.