Towards A Multiscale Model Of Aluminum Corrosion: Atomistic Insights Into Metal Ion Transport At The Water/Alumina Interface

Corrosion pits can form on aluminum surfaces and reduce component lifetimes, but accurately modeling pit growth requires information on the transport rates of dissolved metal ions. Water is both a reactive antagonist and transport medium for corrosion, as it readily adsorbs to the metal and metal oxide (alumina) surface as a thin film. We investigate the properties of the water/alumina interface using molecular dynamics simulations to determine rates for aluminum ion diffusion in the corrosion process. The effects of temperature, Al ion concentration, and relative humidity on the water film’s structure and transport properties are assessed. Ion diffusion rates are highly dampened in adsorbed water films as compared to bulk liquid water due to the combined effects of a strong hydrogen bonding network that forms at the water/oxide interface and polarization at the water surface. A reductionist 1D reaction-diffusion model is used to assess the impact of diffusion rates on corrosion kinetics.

 

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.