A surface analytical study of functionalised mild steel for adhesion promotion of organic coatings

Organosilane compounds are among the most extensively studied compounds in the field of adhesion enhancement of organic coatings on an inorganic substrate. Much of its performance has been related to its ability to form a "bridging effect" at the interfacial region. Nevertheless in order for this to happen, the chemical and physical state of the compound after application on the substrate is very important. Variations in molecular orientation and the chemical state of the compound functionality have been known to give unexpected results on its ability to enhance adhesion of certain organic coatings to a substrate. In this work the nature of 3-aminopropyltriethoxysilane applied on mild steel substrate was studied using X-ray photoelectron and infra-red spectroscopies. It was found that when this compound was applied under common conditions, the amine functional end of the compound appears to bond to the metallic substrate, and that it may be present in the form of a non-protonated amino group or hydrogen-bonded amino group. This "wrong-way round" adsorption is shown to profoundly affect organic coating performance. © 2002 Elsevier Science B.V. All rights reserved.