Influence of the PEO treatment time and sol-gel sealing on the corrosion resistance of AA1050 and AA2024

Plasma Electrolytic Oxidation (PEO) is primarily used as a surface treatment technique to improve the corrosion resistance and mechanical properties of aluminium alloys. This environmentally friendly process uses plasma micro-discharges to produce an adherent, hard and wear resistant oxide layer. Nevertheless, it has certain limitations, notably its high energy consumption and, more significantly, the inherent porosity of the oxide layer, which can compromise both its protective performance and mechanical durability. In this study, a short oxidation time Flash PEO (5 min PEO) combined with sol-gel layer was compared to a conventional PEO process (30 minutes) on both AA1050 and AA2024 alloys in terms of morphology and corrosion performance. The results indicated that 5 min PEO coating produced a compact and thinner oxide layer, provided superior corrosion protection for AA1050 but only short-term protection for AA2024, whereas extended oxidation (30 min) increased structural defects and promoted coating degradation, reducing corrosion resistance of both alloys. Conversely, the subsequent sol-gel impregnation of the porous 30 min PEO layers significantly improved the corrosion resistance and ensured enhanced long-term durability for both AA1050 and AA2024, surpassing the short-term performance of the 5 min PEO coatings.