The Effect of Surface Pretreatment on Water Absorption and Wet Adhesion of Organic Coatings

A study was conducted on the effects of surface pre-treatment with 3- aminopropyltriethoxysilane (3-APS) on the water absorption and adhesion behaviour of two commercial alkyd and epoxy polyamide organic coatings on mild steel and glass substrates. The results indicated that using 3-APS as surface pre-treatment prior to coating resulted in a significant reduction of total water absorption for alkyd on both mild steel and glass substrate. Subsequently ile adhesion of alkyd is enhanced on both pre-treated mild steel and glass substrate. However 3-APS pre-treatment of mild steel increases water absorption of epoxy and lowers its adhesion strength. While 3-APS pre-treatment of glass reduces water absorption of epoxy and subsequently enhances the overall wet adhesion. These data are consistent with the known adsorption behaviour of 3-APS to steel, i.e. as an easily hydrolysed hydrogen-bond to the amine group, rather than as the more stable metal-oxide-silicon bond.