Three thermally cured coatings, formulated on a low Tg isophthalic-based polyester, were investigated by XPS and ToF-SIMS. A model formulation was employed for all three coatings investigated; however, the cross-linking agents used were varied for each formulation. Hexamethoxymethyl melamine (HMMM), tris-isocyanurate (TIC), and a combination of HMMM and TIC were included as the cross-linking agents. The use of TIC alone required a tin-based catalyst to promote the curing reaction.The aim of this work was to investigate the difference in the surface compositions of the three coatings and the distribution of the different cross-linking agents used. This was in preparation for further studies which will involve interfacial analysis in order to elucidate the mechanism responsible for intercoat adhesion.The XPS analysis of the coating surfaces revealed a nitrogen concentration consistent with the concentration expected from the formulation for the coating containing HMMM. In the other two formulations a lower concentration than calculated was observed. The surface concentration of the two cross-linking agents was not influenced by the presence of the others; indeed, the formulation containing both cross-linking agents was, in terms of nitrogen concentration, merely a simple combination of the other two coatings. Peaks diagnostic of the cross-linking agents were observed in ToF-SIMS spectra acquired from the coating surfaces. By using XPS and ToF-SIMS analysis, we could determine that the HMMM and the TIC have a different distribution at the coating surface, that is not affected by the presence of the other.

The adsorption of an acrylated resin, the main component in a commercial UV-cured coating, on hot-dip galvanized steel (HDGS) has been studied. The aim of the work was to understand how the resin is adsorbed onto the different regions (aluminium-rich and zinc-rich) that are representative of the HDGS surface, in order to elucidate the mechanism of the HDGS/coating adhesion.Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed to study the adsorption of the resin. Mass spectra and mass-selected images were recorded in the high-current bunched mode, using Bi 3 + as the primary ion. Scatter ratio plots and relative mass selected images, were used to select the areas of interest for spectral reconstruction.The adsorptions curves were best described by the Langmuir model, indicating that all the adsorption sites are equivalent. The adsorption of the resin leads to the formation of a monolayer on the surface of HDGS.ToF-SIMS ion selected images showed the presence of two well defined regions, aluminium-rich regions and zinc-rich regions. This distinction is not modified by the resin adsorption.The adsorption of the resin was studied independently on aluminium-rich regions and zinc-rich regions. The adsorption curves indicate that the amount of adsorbed resin is almost identical in these two regions, with the formation of a resin monolayer in both cases. These results suggest that the resin/HDGS interaction is comparable in the aluminium-rich and zinc-rich regions.