苯甲酸钠对AM60镁合金在氯化钠溶液中的缓蚀作用

Corrosion inhibition of sodium benzoate for AM60 magnesium alloys in 3.5% NaCl solution

为了改善AM60镁合金的抗腐蚀性能,通过电化学阻抗、极化曲线和浸泡等方法研究了苯甲酸钠(SB)对AM60镁合金在3.5%氯化钠溶液中的缓蚀作用,并考察了温度对缓蚀率的作用规律,借助扫描电镜观察了不同温度和不同SB浓度下镁合金腐蚀后的表面形貌,分析了SB的缓蚀机制。结果表明:SB明显减缓了AM60镁合金的腐蚀速率,当其浓度为0.5mol·L-1时,缓蚀率达到75%以上,这主要是因为SB在AM60镁合金表面发生了物理吸附,这种吸附为放热、熵增的自发过程,形成的多分子吸附层隔离了镁合金和腐蚀介质的直接接触。随着SB浓度增加,镁合金腐蚀反应活化能增大,缓蚀率随之而增大。当SB浓度增大到0.7mol·L-1以后,由于分子间排斥作用占主导作用,导致缓蚀率没有明显增加,且随着温度从25℃升高到70℃,SB的缓蚀率略有下降。

To improve the corrosion resistance of magnesium alloys, corrosion inhibition of sodium benzoate （SB） for AM60 magnesium alloy in 3.5% NaC1 solution and influence of temperature on inhibition efficiency were investigated with electrochemical impedance spectroscopy （EIS）, polarization curves and immersion. Surface morphology of magnesium alloy after corroding with different concentrations of SB at different temperatures was observed with scanning electron microscope （SEM）, and corrosion inhibition mechanism of SB was analyzed. SB reduced obviously the corrosion rate of AM60 magnesium alloy in 3.5% NaC1 solution, and inhibition efficiency was more than 75% at 0.5 mol ·L-1SB. Physical adsorption of SB occurred on AM60 magnesium alloy, and it belonged to an exothermic, entropy increase and spontaneous process. A multi-molecular adsorption layer was formed on the magnesium alloy surface to prevent the magnesium alloy from contacting corrosive solution. The activation energy for the corrosive reaction increased with increasing SB concentration, resulting in increasing inhibition efficiency. When SB concentration was up to 0.7 tool·L-1, inhibition efficiency did not increase, because intermolecular repulsion dominated with increasing SB concentrations. Moreover, inhibition efficiency did not increase when temperature changed from 25℃ to 70℃.