Electrochemical Performance of a Novel Al-Zn-In-Sn-La Sacrificial Anode Alloy in Simulated Marine Environments
Taking the commercial sacrificial anode alloy Al-Zn-In as reference,a novel alloy Al-Zn-In-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,open-circuit 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 com-mercial 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 commer-cial alloy in shallow sea condition,similarly,that was 82.99％and 75.48％in the deep-sea conditions,re-spectively.All the actions of the low free-corrosion rate of the alloy,the weakened micro-galvanic ef-fect 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 improve-ment 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.
Al alloy sacrificial anodesimulated marine environmentdischarge capacitycurrent effi-ciency
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