材料期刊网

为了研究AZ31镁合金微弧氧化(MAO)涂层腐蚀速率的数学模型，选取不同的过程参数(包括脉冲频率、电压、氧化时间和电解液浓度)，采用微弧氧化技术和磷酸三钠电解液体系，在镁合金基体上制备了耐蚀涂层。研究了不同脉冲频率下制备的MAO涂层在仿生体液中浸泡1、5和7 d后的极化曲线，测试了不同条件下制备的镁合金 MAO 涂层在浸泡不同时间后的腐蚀电流密度，对不同微弧氧化过程参数及浸泡时间进行了主成分分析，建立了腐蚀速率的数学模型。结果表明，MAO涂层的腐蚀电流密度小于镁合金基体，脉冲频率对腐蚀速率起主导作用。将不同过程参数下制备的镁合金 MAO 涂层在仿生体液中浸泡24 h，利用Tafel曲线拟合得到的腐蚀电流密度与由回归方程计算所得的模拟电流密度相比，相对误差小于5%，而且其多元评定系数为0.9021，表明所建立的回归方程能可靠地用来模拟不同参数下制备的镁合金 MAO 涂层在浸泡不同时间下的腐蚀电流密度，为预测和控制镁及镁合金 MAO 涂层的腐蚀速率提供指导。

The mathematical model for corrosion rate of a micro-arc oxidation (MAO) coating on AZ31 magnesium was studied. The corrosion resistant coating on AZ31 Mg alloys was prepared from a Na3PO4 bath by MAO technology using various parameters including pulse frequency, voltage, oxidation time, and electrolyte concentration. The polarization curves for MAO coatings prepared at different pulse frequencies after immersion in simulated body fluid (SBF) for 1, 5, and 7 days were examined. The corrosion current densities of the MAO coatings prepared under different conditions after immersing for different time were measured. The principal component analysis for various parameters of MAO process and immersion time in SBF was carried out. A mathematical model for corrosion rate was established. The results showed that the corrosion current density of MAO coating is smaller than that of untreated Mg alloy substrate. Pulse frequency plays a leading role for corrosion rate. The relative error of the corrosion current density fitted by Tafel curves for the MAO coatings prepared under different process parameters after immersion in SBF for 24 h is less than 5%, as compared with the corrosion current densities calculated by using the regression equation. The coefficient of multiple determination is 0.902 1, implying that the regression equation can be reliably used for predicting the corrosion current densities of MAO coatings prepared on magnesium alloy under various parameters and immersed in SBF for different time. The method can be used for predicting and controlling the corrosion rates of MAO coatings on Mg and Mg alloys.