Study of the corrosion of aluminum by CCl4 using inelastic electron tunneling spectroscopy

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Abstract
Inelastic electron tunneling spectroscopy (IETS) has been used to determine the molecular species which occur on an aluminum oxide surface during metallic corrosion by carbon tetrachloride. IETS spectra were obtained for CCl4 adsorbed on aluminum oxide and the observed vibration modes were assigned by comparison with infrared and Raman frequencies. Modes were observed which could be associated with the molecular species CCl4, AlCl, AlCl2, AlCl3, ⋅CCl3, C2Cl6, and the complex CCl+3[AlCl4]−. These species are those in the reaction sequence proposed by Stern and Uhlig for the corrosion of aluminum by CCl4. The results do not provide information on whether the reaction is chemical or electrochemical in nature. The fact that no modes were observed which would reflect oxygen–carbon bonding, and the presence of a large number of aluminum–chlorine modes suggest that the corrosion mechanism is by reaction of the solvent with exposed aluminum atoms.
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