ESCA and AES Studies of the Interfacial Chemical Bonding Between Aluminum and Chromium (III) Fumarato-Coordination Compound

Abstract

The chromium(III) fumarato-coordination compound, commercially known as Volan 82, is a coupling agent developed by DuPont in the early 1970s. It has proven to be a very successful bonding agent between aluminum and polyethylene. Aluminum foil treated by aqueous chromium(III) fumarato-coordination compound solution can be coated with polyethylene to form water-resistant and durable composite film which is a useful packaging material and a composite shielding for wire cable. We wish to report the application of ESCA and AES in the study of the interfacial chemical bonding between aluminum and chromium(III) fumarato-coordination compound. The ESCA and SIMS analyses of the aluminum surface treated by aqueous chromium(III) fumarato-coordination compound solution show that chromium is retained on the surface. The spatial distribution of chromium on the aluminum surface was studied by Scanning Auger Microprobe. The Auger images of Al and Cr show that Cr Silver was partly deposited on the aluminum foil followed by treatment with chromium (III) fumarato-coordination compound. Auger line scan shows that Al, O and Cr have the same distribution on this line. The AES depth profile indicates that chromium (III) fumarato coordination compound is bonded not only with the outermost layers of aluminum oxide but also with the sub-surface layers of aluminum oxide on the aluminum surface. The ESCA technique was also used to study the Al 2p binding energy chemical shift. On the untreated aluminum foil surface, the aluminum atoms exits in two chemical forms: metallic Al 2p binding energy of 72.4 eV, and Al2)3 with Al 2p binding energy of 74.8 eV. After the aluminum foil was treated by aqueous chromium (III) fumarato solution, the ESCA Al 2p peak was obviously broadened, the reacted Al2O3 binding energy shifted to 75.2 eV. Apparently, the chemical bonding between Al2O3 and chromium (III) fumarato coordination compound causes a chemical shift of Al2O3 Al 2p binding energy by 0.4 eV. The compositional change within the aluminum-polyethylene interface of the composite film was measured by AES depth profile technique. ESCA was used to measure the Al 2p binding energy at different levels within the interface. The results indicate that in the aluminum-polyethylene interface aluminum atoms exits in three chemical forms: metallic Al,unreacted Al2O3 and Al2O3 chemically bonded with chromium (III) fumarato coordination compound the existence of these three forms of aluminum atoms confirms the chemical bonding mechanism between aluminum and the coupling agent.