Study of ZnAl Hydroxides-Based Thin Films to Enhance the Filiform Corrosion Resistance of Acrylic-Coated AA5005

Abstract

In recent years, the imperative to adopt a sustainable approach to aluminum pre-treatments due to environmental concerns has engaged researchers in corrosion studies. This work investigates Zn-Al hydroxides-based conversion coatings developed on AA5005 to enhance filiform corrosion (FFC) resistance. In fact, the conversion coatings were applied as a pre-treatment (200-800 nm thick, depending on synthesis conditions) prior to coating with acrylic paint. The synthesis of the Zn-Al hydroxides conversion coating involves a rapid hydrothermal method at near-neutral pH. Electrochemical tests performed on the ZnAl hydroxides conversion coatings onto AA5005 revealed a substantial improvement in localized corrosion. FFC tests in a climatic chamber exhibit a significant decrease (about 50%) in rust creep filament propagation compared to bare AA5005 after 1000 hours. Those results were obtained employing Zn and Al salts at neutral pH for ten minutes at 95°C. The findings obtained suggest that the synthesis process is of potential interest within the context of chemical surface conversion treatments for aluminum. In fact, eco-friendly metallic salts contribute to a more economical and environmentally friendly waste disposal process, making this treatment a potential solution for industrial applications, considering its simplicity, time efficiency, and use of non-toxic products.

Exploring the Role of Passivating Conversion Coatings in Enhancing the Durability of Organic-Coated Steel Against Filiform Corrosion Using an Electrochemical Simulated Approach

“…By harnessing the potential of CCs and considering their strategic placement within a coating system, their aptitude for mitigating FFC becomes a salient feature. Extensive research has been conducted to examine the influence of multiple conversion coatings on the manifestation of FFC, specifically on aluminum substrates coated with organic coatings, yielding encouraging findings [22,[29][30][31][32][33][34][35][36]65]. However, to the best of current knowledge, there is no available reference concerning the utilization of CCs in painted steel protection with a specific focus on FFC.…”