XPS, AES AND RAMAN STUDIES OF AN ANTITARNISH FILM ON TIN

For protecting tin from tarnishing, ethylenediamine-tetramethylidene-phosphonic acid (EDTMP) was found to be more effective than chromate, molybdate, and other agents. A 10-minute treatment in 5 to 10 g/L of EDTMP with a pH of 1 to 4 at 25 to 80-degrees-C formed a corrosion-resistant complex film, which was composed of 48.0% O, 10.7% Sn, 7.7% N, 23.1% C, and 10.5% P, based on x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) determinations. From differences in the binding energies of Sn, N and O before and after film formation, and from the R-PO3(2-) and Sn-N vibrations in the Raman spectra for the film it was deduced that N and O in EDTMP were coordinated with Sn in the film.