Electrodeposited lanthanum film as chromate replacement for tinplate

The lanthanum film as chromate replacement was prepared on tinplate by the electrodeposition method. Sulfide-stain resistance of the La-passivated, unpassivated and Cr-passivated tinplates was evaluated using a cysteine tarnish test. Corrosion behavior of these tinplates in 0.1 M citric-citrate buffer solution was investigated using electrochemical impedance spectroscopy (EIS). The composition and thickness of the lanthanum film were studied using X-ray photoclectron spectroscopy (XPS) and X-ray fluorescence spectrometry (XR-F). According to the results, the lanthanum film significantly improves protection of tinplate against sulfide-stain and corrosion. In comparison to the Cr-passivated tinplate, the La-passivated tinplate exhibits better sulfide-stain resistance and similar corrosion resistance. The lanthanum film mainly consists of La2O3 and its hydrates such as La(OH)(3) and La2O3 center dot H2O. The total lanthanum amount of the film is 0.0233 g/m(2) (c) 2007 Elsevier B.V. All rights reserved.