Al-Zn-In系牺牲阳极在模拟海洋环境下的电化学性能研究

Electrochemical Performance of a Novel Al-Zn-In-Sn-La Sacrificial Anode Alloy in Simulated Marine Environments

在商用Al-Zn-In牺牲阳极基础上,自行设计冶炼了Al-Zn-In-Sn-La牺牲阳极合金,并在模拟浅海和深海环境下,测试了两种合金的开路电位、动电位极化曲线、恒电位极化曲线、腐蚀失重等,对比分析讨论了两种牺牲阳极的放电量和电流效率。结果表明:模拟海洋环境下,冶炼合金放电量较商用合金略有提高,这与In、Zn、Sn协同活化作用破坏钝化膜完整性、增加钝化膜阴阳离子空位促进离子迁移有关。同时,冶炼合金电流效率较商用合金显著提高,浅海环境下电流效率由75.87%提高至90.01%,深海环境下由75.48%提高至82.99%。冶炼合金自腐蚀速率低、晶界偏析相与基体电位差较小导致微电偶作用减弱、稀土元素细化晶界促进均匀溶解等共同作用提高了电流效率。模拟深海环境下,两种合金的放电量较浅海环境大幅降低,这主要是由于低温、低含氧量导致离子溶解沉积速率降低,牺牲阳极活性点减少,Al合金牺牲阳极发生钝化。为克服深海放电量低下的问题,高熵合金的思路也许能显著提高活化合金元素的固溶度,从而提高其深海放电性能。

Taking the commercial sacrificial anode alloy Al-Zn-In as reference,a novel alloy Al-ZnIn-Sn-La was designed and made.Then the performance of the two alloys in simulated conditions of shallow-sea and deep-sea was comparatively assessed via measurements of corrosion mass loss,opencircuit potential,potentiodynamic polarization curves,and potentiostatic polarization curves.Results showed that,the discharge capacity of the Al-Zn-In-Sn-La alloy was slightly higher than that of the commercial Al-Zn-In alloy in the simulated marine environments,which may be related to the breakdown of the integrity of the passive film and the improvement of the anion and cation vacancies of the passivation film to promote ion migration,due to the synergistic activation effect of In,Zn,and Sn.Meanwhile,the novel alloy presents current efficiency of 90.01%,which was much higher than 75.87%of the commercial alloy in shallow sea condition,similarly,that was 82.99%and 75.48%in the deep-sea conditions,respectively.All the actions of the low free-corrosion rate of the alloy,the weakened micro-galvanic effect between the precipitated phase along grain boundaries with the matrix,and the refinement of grain boundaries by rare earth elements to promote uniform dissolution may significantly promote the improvement of the current efficiency of the novel alloy.It is worth mentioning that,the discharge capacity of the two alloys are significantly reduced in the simulated deep-sea environment.Which may be ascribed to the lower temperature and oxygen content,the slow-down of dissolution and deposition rate of ions,which reduces the surface-active sites of the alloys,leading to the passivation of the sacrificial anode Al-based alloys.It is expected that the designment of high entropy alloys might be an effective approach to overcome the problem of low discharge capacity of sacrificial anode alloys in deep-sea environment,by significantly improving the solubility of active alloying elements,and thereby improving the deep-sea discharging performance.