Feng Zhiyuan, Li Jichao, Yang Zi, Buchheit Rudolph
Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40502, USA.
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA.
Materials (Basel). 2020 Mar 14;13(6):1325. doi: 10.3390/ma13061325.
The anodic polarization response of magnesium alloy AZ31 was first characterized during exposure to aerated 0.1 M NaCl solutions with millimolar additions of NaVO, NaPO, NaHPO, NaF and various pairings to assess their ability to inhibit corrosion kinetics and retard localized corrosion. Each of the candidate inhibitors reduced the corrosion rate of the alloy to some degree. A NaPO-NaVO pair produced a good inhibiting effect decreasing the corrosion rate to about 10 A/cm, which was two orders of magnitude lower than the uninhibited control case. A Bliss Independence assessment indicated that this inhibitor pair acted synergistically. A NaHPO-NaVO pair reduced the corrosion rate to 10 A/cm but was not assessed to be acting synergistically. The NaVO-NaF pair did not reduce the corrosion rate significantly compared to the control case and was an antagonistic pairing. SEM imaging showed film formation due to exposure, which appears to be the origin of the observed inhibition. The resistance to localized corrosion was assessed as the difference in the breakdown potential and the corrosion potential, with larger values indicating a lower probability of localized corrosion during free corrosion exposures. The effects of the inhibitors on this characteristic were mixed, but each of the inhibitor pairs yielded potential differences in excess of 100 mV. A conceptual conversion coating process based on a mixture of vanadate and phosphate compounds were demonstrated. A fluoride-bearing formulation produced coatings whose total impedance was increased by a factor of two compared to an uncoated control. A fluoride-free formulation produced coatings whose corrosion resistance was increased by more than a factor of three.
在暴露于含有毫摩尔级添加物NaVO、NaPO、NaHPO、NaF及各种组合的曝气0.1M NaCl溶液中时，首次对镁合金AZ31的阳极极化响应进行了表征，以评估它们抑制腐蚀动力学和延缓局部腐蚀的能力。每种候选缓蚀剂都在一定程度上降低了合金的腐蚀速率。NaPO-NaVO组合产生了良好的抑制效果，将腐蚀速率降低到约10 A/cm，这比未添加缓蚀剂的对照情况低两个数量级。布利斯独立性评估表明，这种缓蚀剂组合具有协同作用。NaHPO-NaVO组合将腐蚀速率降低到10 A/cm，但未评估其具有协同作用。与对照情况相比，NaVO-NaF组合没有显著降低腐蚀速率，是一种拮抗组合。扫描电子显微镜成像显示暴露后形成了膜，这似乎是观察到的抑制作用的根源。通过击穿电位和腐蚀电位的差值来评估耐局部腐蚀性能，差值越大表明在自由腐蚀暴露期间发生局部腐蚀的可能性越低。缓蚀剂对这一特性的影响各不相同，但每种缓蚀剂组合产生的电位差都超过了100 mV。展示了一种基于钒酸盐和磷酸盐化合物混合物的概念性转化涂层工艺。一种含氟配方制备的涂层，其总阻抗相比未涂层的对照增加了一倍。一种无氟配方制备的涂层，其耐腐蚀性提高了三倍多。
