Exploring the Performance of Phosphate-Functionalized Waterborne Binders on AZ31 Magnesium Alloy

Organic coatings are among the most effective solutions to enhance the corrosion resistance of metals. Traditionally, solvent-based coatings have been widely used in industrial applications. However, due to environmental regulations, water-based coatings are in demand due to their lower toxicity. One of the main challenges associated with water-based coatings is how to avoid flash rust corrosion on the metal/coating interface. Typically, this phenomenon is mitigated by incorporating additives such as inorganic corrosion inhibitors. An alternative is the novel approach of using phosphate-functionalized waterborne binders, which has only been explored on mild steel [1].

In the present work, a waterborne binder (consisting of methyl methacrylate (MMA) and butyl acrylate (BA)) was obtained using a polymerizable phosphate-based surfactant and applied on AZ31B magnesium alloy. Different surface pretreatments were used to explore the adhesion and corrosion performance: a) mechanical grinding, b) chemical cleaning, c) zirconium conversion coating (ZrCC), and d) layered double hydroxides (LDHs). The coated samples were cured in a climatic chamber at 23ºC for 24 hours under 60% of relative humidity.

This study included sample characterization in terms of morphology and composition through SEM-EDX and the evaluation of corrosion protection using EIS in a 3.5 wt. % NaCl solution. Additionally, water contact angle measurements and roughness parameters were evaluated.