FTIR and XPS study of the adsorption of probe molecule used to model alkyd resin adhesion to low carbon aluminum killed steel

An important factor in achieving maximum adhesion of a particular coating system to the substrate lies in the proper pre-treatment of the substrate prior to the application of the coating. The Lewis acid–base properties of the outer metal surface play a determining role in many of these applications, and the chemical reactions involved therein. In this work, the Lewis nature of the low carbon aluminum killed (LCAK) substrate has been significantly modified by a chemically activated surface pre-treatment. The wetting properties of the LCAK substrate was determined by contact angle measurements; the coordination of the chemical species on the surface was studied with XPS; FTIR together with the probe molecule (B(OCH3)3) was used to explain the chemical bonding. The novel combination of contact angle, XPS, FTIR and probe molecule enabled the determination of the Lewis acid–base properties of the LCAK surface before coating. The XPS spectra of the LCAK surface rinsed in warm water show that the surface species differ from that rinsed in tap water. With change in pH, the wettability properties also drastically changed. The probe molecule (B(OCH3)3) did not bond on the warm water rinsed samples but bonded strongly on tap water rinsed samples as the pH decreased. This research has shown that Lewis acid–base properties can be significantly changed with water temperature and pH, which has important implications for industrial pre-treatment.