(Digital Presentation) Pinpointing the Potential-of-Zero-Charge in a Alumina-Coated Aluminum/Water Interface Model for Corrosion Applications

Abstract

The surfaces of most metals immersed in electrolytes feature a several nanometer-thick oxide/hydroxide layer in aqueous electrolytes. This leads to the existence of both a metal/oxide and an oxide/liquid electrotlyte interface. The resulting complexity, and the uncertainty about the structure of and the charges on the surface films, make it challenging to predict from first principles the potential-of-zero-charge (PZC) which has been correlated to the pitting potential [1]. In this work, we use large-scale Density Functional Theory and ab initio molecular dynamics to calculate the PZC of a Al(111)|gamma-Al(2)O(3)|water model within the context of aluminum corrosion. By partitioning the multiple, complex interfaces involved into binary components with additive contributions to the overall work function and voltage, we calculate the PZC in liquid water for this model. Simultaneously, we calculate the orbital energy levels of defects like oxygen vacancies in gamma-Al(2)O(3), which are critical parameters in theories associated with pitting corrosion onset. Our predictions align the Fermi level at PZC with oxygen vacancy impurity defect levels, and estimate the voltage needed to generate charged oxygen vacancies in the flat band approximation. The similarities and differences in results and assumptions used between our model calculations and experiments will be discussed.[1] J.~O'M. Bockris and Y.~Kang, J. Solid Electrochem. 1:17 (1997).Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the document do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Figure 1