Evaluation of surface pretreatment methods on thin austenitic stainless steel foils for adhesive bonding applications

Abstract

ABSTRACT Stainless steel is used across all industries, from the chemical or construction sector to household appliances. To produce load bearing joints, a surface treatment of the passive surface of austenitic stainless steel is generally necessary. However, the treatment of thin-walled foil materials inhibits challenges concerning the deformation under thermal loads. This work investigates the effectiveness and mechanisms of different surface treatments on 50 µm thin AISI 316 L steel foil. Basic cleaning, surface finishing with an aluminum oxide abrasive, flame-pyrolytic deposition of silicon dioxide and application of a primer, etching with hydrochloric acid, treatment by atmospheric plasma, ns-pulsed laser surface cleaning, and fs-laser structuring are investigated. The effects of these treatments are analyzed in surface energy investigations by contact angle measurement, roughness measurements, and SEM-EDX. The bonding strength is tested with epoxy adhesives and a methyl methacrylate adhesive under 90° peel load. The failure mechanisms are further investigated by FTIR spectroscopy and SEM-EDX. The results show that the used coating with primer produces the strongest bonds, followed by the fs-laser treatment. In particular, sub-microscopic surface structures induced by fs-laser show promising results. SEM images show a full wetting of the capillary structures, providing the possibility of mechanical interlocking on a sub-microscopic level.