Effect of atmospheric corrosion on Al and Ti thin film deposited on steel surface in urban region

Abstract

Pure metals Aluminum (Al) and Titanium (Ti) thin films have been deposited on steel by using physical vapor deposition. The effect of these protective layers on atmospheric corrosion steel surface have been investigated after exposure the samples for one year to urban atmosphere. The rust morphology observed using Scanning Electronic Microscope (SEM) analysis consists of a cotton ball structure for the steel samples coated with Al, and flowery structure for samples coated with Ti. The Raman spectroscopy (RS) used in this study consolidates deeply the information about the structure of the rust layer. The Al coating shows the predominance growth of iron oxide as goethite. However in case of uncoated steel or Ti coating, the oxide structure was principally lepidocrocite. Raman shifting to high wavenumber values gave stretching corresponding to diaspore. The comparison of Raman bands for the Ti coating on steel to the literature suggests that in our case the Ti films are not converted to a protective layer of anatase or rutile during exposure. This result can explain the important growth of the rust layer in atmosphere and suggest that Ti acting as a getter for atmospheric pollutant. However, the Al steel coating present an interesting resistant to atmospheric corrosion.