The coating application for enhanced adhesion between GFRP composites and cataphoresis-coated (KTL) steel – part 2: surface properties

Purpose This study examines the effect of increased surface energy on adhesion strength. Surface modifications were made using chemical coating methods such as primer paint (primer) and cataphoresis (KTL, Kathodische Tauchlackierung). The wetting behaviour of adhesive on these surfaces and the resulting contact angles were analysed to evaluate bonding effectiveness. Design/methodology/approach Primer paint was applied to glass fibre reinforced plastic (GFRP) materials and cataphoresis coating was applied to steel. Contact angles of the coated surfaces were measured and compared to those of the uncoated (natural) surfaces. Findings Results showed that applying primer to GFRP and KTL to steel increased their surface energy compared to untreated surfaces. A decrease in contact angle correlated with improved wetting, suggesting enhanced adhesion potential. Originality/value While the effects of surface coatings on adhesion have been studied, there is limited research specifically on the adhesion-enhancing potential of KTL coatings. Typically used for corrosion resistance, KTL is shown here to also improve adhesion. The novelty lies in experimentally demonstrating KTL’s dual role as both a protective and adhesion-enhancing layer.