First principle calculations of aluminum destruction caused by chloride ions - effect of interstitial chloride ions, charging and hydrogen

摘要

In this work, several atomic models concerning the surface destruction of bare aluminum (Al) have been explored based on density functional theory (DFT). The aim is to determine the effect of interstitial chloride ions (CT), charging, as well as hydrogen (in atomic form, H). The current study suggests that the total energy increases as Cl~- approaches the Al surface. Furthermore, the optimum path when Cl~- transfers towards and through the Al surface can be predicted by the calculated energy barrier. Stable positions for Cl~- are found at some interstitial sites beneath the Al surface. The effect of interstitial Cl~- on the transferring behavior of subsequent Cl~- has also been studied. In our previous work it was concluded that it is difficult for Cl~- to destroy the Al surface when the Cl~- coverage is less than 2/3 of a monolayer (ML). Whereas in this work the focus is on much lower Cl~- coverage (ML < 1/3) and also involves some other prerequisites that are important for Al corrosion - charge and hydrogen. Charging of a system can greatly affect electrochemical processes on the Al surface. Hydrogen embrittlement is common in some Al alloys and H also takes part in some electrochemical reactions. Through structural and electronic analysis, it is shown herein that the destruction of the Al surface will be aggravated by charging the system in the presence of H. In addition, a special substructure has formed as a reaction product even when the Cl~- coverage is low (ML < 1/3).