Silanes as adhesion promoters in waterborne epoxy paints

Abstract

The aim of this work was to study mercaptopropyltrimethoxysilane (MTMO), aminopropyltrimethoxy silane (AMEO) glycidoxypropyltrimethoxysilane (GLYMO) and glycidoxypropyltriethoxysilane (GLYEO) as adhesion promoters between an epoxy waterborne paint and electrogalvanized steel. The metallic substrate was brushed with hot water and detergent, electrochemically cleaned, immersed in the hydrolysed silanes solutions and dried at 110 ºC for 1 h. Finally, the pretreated substrates were paint by brush. The paint used was an epoxy-poliamidoamine whose dried film thickness was 85±15 m. As control a replicate of the substrate without silane pretreatment was used (Z). After curing, the painted samples were exposed in the salt spray or in the humidity chambers. Rusting and blistering degrees, adhesion and failure at the scribe were evaluated along the exposure. The experimental results showed differences among the pretreatments performance, especially in the loss of adhesion and failures at the scribe. The paint on both the GLYEO pretreated and the Z samples lost most of its adhesion after 30 days of exposure in the chambers. For the MTMO pretreated and the Z samples the failure at the scribe started to be important after 30 days in the salt spray chamber, while for the GLYEO pretreated samples it occurred after 60 days in the humidity chamber.