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首页> 外文期刊>Faraday discussions >In situ monitoring of corrosion mechanisms and phosphate inhibitor surface deposition during corrosion of zinc-magnesium-aluminium (ZMA) alloys using novel time-lapse microscopy
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In situ monitoring of corrosion mechanisms and phosphate inhibitor surface deposition during corrosion of zinc-magnesium-aluminium (ZMA) alloys using novel time-lapse microscopy

机译：使用新型延时显微镜对锌-镁-铝（ZMA）合金腐蚀过程中的腐蚀机理和磷酸盐抑制剂表面沉积进行原位监测

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In situ time-lapse optical microscopy was used to examine the microstructural corrosion mechanisms in three zinc-magnesium-aluminium (ZMA) alloy coated steels immersed in 1% NaCl pH 7. Preferential corrosion of MgZn2 lamellae within the eutectic phases was observed in all the ZMA alloys followed by subsequent dissolution of Zn rich phases. The total extent and rate of corrosion, measured using time-lapse image analysis and scanning vibrating electrode technique (SVET) estimated mass loss, decreased as Mg and Al alloying additions were increased up to a level of 3 wt% Mg and 3.7 wt% Al. This was probably due to the increased presence of MgO and Al2O3 at the alloy surface retarding the kinetics of cathodic oxygen reduction. The addition of 1 x 10(-2) mol dm(-3) Na3PO4 to 1% NaCl pH 7 had a dramatic influence on the corrosion mechanism for a ZMA with passivation of anodic sites through phosphate precipitation observed using time-lapse image analysis. Intriguing rapid precipitation of filamentous phosphate was also observed and it is postulated that these filaments nucleate and grow due to super saturation effects. Polarisation experiments showed that the addition of 1 x 10(-2) mol dm(-3) Na3PO4 to the 1% NaCl electrolyte promoted an anodic shift of 50 mV in open circuit potential for the ZMA alloy with a reduction in anodic current of 2.5 orders of magnitude suggesting that it was acting primarily as an anodic inhibitor supporting the inferences from the time-lapse investigations. These phosphate additions resulted in a 98% reduction in estimated mass loss as measured by SVET demonstrating the effectiveness of phosphate inhibitors for this alloy system.
机译：用原位延时光学显微镜检查了三种浸在1％NaCl pH 7中的锌-镁-铝（ZMA）合金涂层钢的显微组织腐蚀机理。 ZMA合金，随后溶解富锌相。当镁和铝合金的添加量增加到3％（重量）Mg和3.7％（重量）时，使用延时图像分析和扫描振动电极技术（SVET）估算的质量损失，腐蚀的总程度和速率降低了。 。这可能是由于合金表面MgO和Al2O3的存在增加，阻碍了阴极氧还原的动力学。在1％NaCl pH 7中添加1 x 10（-2）mol dm（-3）Na3PO4会对ZMA的腐蚀机理产生重大影响，通过时移图像分析观察到，ZMA的阳极通过磷酸盐沉淀而钝化。还观察到令人着迷的丝状磷酸盐的快速沉淀，并且推测这些丝由于超饱和效应而成核并生长。极化实验表明，向1％NaCl电解质中添加1 x 10（-2）mol dm（-3）Na3PO4可以促进ZMA合金在开路电势下发生50 mV的阳极移位，而阳极电流降低2.5数量级表明它主要是作为阳极抑制剂，支持了时移研究的推论。这些添加的磷酸盐使通过SVET测得的估计质量损失降低了98％，这证明了磷酸盐抑制剂对该合金体系的有效性。

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