CORE AND VALENCE-BAND PHOTOELECTRON SPECTROSCOPIC STUDIES OF NICKEL INTERACTION WITH ETIDRONIC ACID

The corrosion behavior of nickel metal in both sodium chloride and etidronic acid (EDA) solutions was studied by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy. A polymer film was found to form on the surface of the unoxidized metal after treatment with 1 M EDA. This polymer film can effectively prevent the corrosion of nickel by chloride ions. Sodium chloride solution appears to increase the thickness of the polymer film, and no phosphorous was detected in the film. This indicates that the film was formed by decomposing EDA, rather then by simple adsorption of EDA on the nickel surface. The film was so thick that no nickel XPS signal from the metal and/or its oxides could be seen. The XPS and infrared results were consistent with an oxidized hydrocarbon film containing ether and hydroxide groups. Nickel oxide or oxidized nickel metal exposed to EDA led to the formation of nickel etidronate rather than the polymer film.