Adhesive bond durability and corrosion resistance of AA6060-T6 flash-PEO treated in Mo-Si solutions

Aluminium adhesive bonding is a key enabler in lightweighting engineering structures, directly influencing global energy consumption and carbon emissions. Plasma electrolytic oxidation (PEO) has recently emerged as an environmentally friendly alternative to industry-standard sulphuric acid anodising (SAA) surface preparation prior to bonding. However, little is known about the longer-term durability of adhesively bonded PEO-treated structures. Here, AA6060-T6 Al alloy samples were subjected to unconventionally brief 70-s flash-PEO treatments using high-frequency 2.5 kHz unipolar and bipolar pulsed polarisation in aqueous alkaline electrolytes containing Na 2 SiO 3 and optionally Na 2 MoO 4 . Molybdate addition and bipolar polarisation improved uniformity and corrosion resistance of thin, ~1 μm, oxide layers produced. All studied flash-PEO coatings performed well in lap shear tests, exhibiting adhesive strength comparable to that of sealed SAA films and demonstrated equivalent or enhanced bond durability when tested after 1008-h Sea Water Acetic Acid Test exposure, indicating satisfactory resistance to moisture and corrosion with preferential adhesive fracture. Comparable to SAA, the long-term bonding performance of flash-PEO treatments highlights their potential as a sustainable surface preparation route for aluminium adhesive bonding.