Water adsorbed at various temperatures in the range 373–873K on chromium, iron, nickel and stainless-steel plates was studied by temperature-programmed desorption (TPD) under vacuum (10−6hPa). Three states were distinguished: state I due to weakly chemisorbed water and states II and III probably associated with hydroxyl groups bound to different sites. Water is adsorbed mainly in states I and II at temperatures T0<500K and in state III at T0>600K. These states were present in all the metals which were studied except in iron that did not show state I. TPD spectra of water from stainless steel are explained by the presence of Cr and Fe in the form of oxides at the substrate surface. The heat of adsorption in state I and the activation energies of desorption in states II and III were found around 100–120, 170–190 and 220–270kJmol−1, respectively.

Abstract In this study, we investigated the reactivity of chromium, iron, and surface-treated 304L stainless steels (SS) toward molecules representing model epoxy resins. These molecules were ammonia (a basic probe molecule also representative of the hardener amine group), 1,2-epoxybutane (for epoxy groups) and 2(methylamino)ethanol (for the β-amino alcohol resulting from the reaction of epoxy with amine). These molecules were analyzed in the adsorbed state by either FT-IR or temperature-programmed desorption (TPD). Surface analysis showed that the top surface of the treated 304L samples only contains chromium and iron as metallic elements. The chromium/iron ratio can be varied within a wide range according to the SS surface treatment used. When increasing the SS surface chromium enrichment, we show a simultaneous increase of (i) both density and strength of surface acid sites, (ii) the amount of β-amino alcohol adsorbed. In addition, there is a marked improvement of the epoxy resin/304L bond strength when the SS surface is more chomium-enriched.

The surface of hot-dip galvanized steels is a complex system highly dependent upon the composition of the galvanization bath and upon surface treatments such as degreasing, alkaline etching and chromate conversion. In this study, industrial zinc-coated samples are subjected to degreasing, alkaline etching and chromating and then characterized by XPS and Fourier transform infrared spectroscopy (FTIR). Their surface reactivity is studied by vapour-phase adsorption of probe molecules, either basic (pyridine) or acidic (phenol), and FTIR analysis. The reactivity enhancement following the alkaline etching is clearly evidenced by this technique. in order to gain information upon the reactivity of the hot-dip galvanized steel surface towards some organic components of epoxy resins, dicyandiamide adsorption was performed at 180 degrees C on the chemically treated substrates. As suggested by the results obtained with probe molecules, alkaline etching of galvanized steels allows a dicyandiamide-zinc reaction leading to the formation of a defined complex, In addition, the study of the interaction of model substrates (pure zinc and aluminum-contaminated pure zinc) with dicyandiamide clearly shows that surface contamination of galvanized steels by aluminium is responsible for the inhibition of the dicyandiamide-zinc reaction.

This paper describes how the temperature-programmed desorption (TDP) technique, which is widely used in the fields of surface science and catalysis, has been newly adapted to investigate the thick metallic sheet samples of about 10 cm(2) area used in adhesion studies. A high frequency induction system has been designed in order to achieve a high heating tate (up to 200 K.s(-1))without creating substantial temperature gradients in the sheet The sample is placed in a secondary vacuum reactor and the gas desorbed is analysed by means of a quadrupole mass spectrometer. The results presented deal with stainless steel and chromium surfaces, subjected to various chemical treatments. The sensitivity and the resolution of the technique presented are shown to be sufficient to study metallic surface contamination and to characterise the acid sites at the surface by desorption of a basic probe molecule such as ammonia.