图6是清漆和树脂涂层的电荷转移电阻Rt随时间T的变化曲线,Rt可以表征金属界面发生腐蚀的难易程度,Rt的值越大,说明腐蚀反应越不容易进行[19]。由图可知,树脂涂层和清漆涂层的电荷转移电阻Rt都是先略有降低再增大后减小的变化规律,电阻增大是因为在腐蚀反应前期产生的难溶物质在一定程度上阻拦了溶液中氯离子的进入,后期由于腐蚀产物的逐渐溶解而脱落使反应电阻减小,在2016h时树脂涂层的涂层电阻Rt迅速降低,与环氧涂层的Rt相当,且不再增大,这是因为涂层已经遭到破坏,在整个过程中树脂涂层的涂层电阻Rt均高于清漆涂层,说明树脂涂层发生腐蚀比清漆涂层困难,表明添加丙烯酸树脂可以提高环氧树脂涂层的防腐蚀性能。
2.2.4 浸泡实验后涂层下镁合金的表面形貌
图7为两种涂层试样在质量分数3.5%氯化钠中浸泡5000h,除去被腐蚀部分的涂层后镁合金的腐蚀形貌结果。从宏观上看,浸泡后的涂层下镁合金都发生了均匀腐蚀,但树脂涂层表面上还有没被腐蚀的区域,而清漆涂层表面已经全面腐蚀。在剥腐蚀涂层表面涂层时树脂涂层仍有阻力不能轻易脱落,而清漆涂层直接整块脱落,说明树脂涂层腐蚀程度较轻。因此,在环氧树脂中加入丙烯酸树脂可以提高涂层的保护效果,这与前面SEM图和电化学结果相一致。
3结论
1)合成的丙烯酸树脂有良好疏水性。
2)与环氧树脂清漆涂层相比,添加了丙烯酸树脂的涂层层间附着力、耐冲击性和疏水性均有提高。
3)与环氧树脂清漆涂层相比,添加了丙烯酸树脂的涂层,防腐蚀性能更优。
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音乐:And I You-Giovanni Marradi
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