In-situ phosphatization of waterborne acrylic latex coatings for long-term corrosion protection of metal without flash rust

Abstract

Waterborne acrylic coatings are widely utilized due to their cost-effectiveness, high transparency, strong resistance to weather and chemicals, impressive mechanical properties, and excellent adhesion to various substrates. In these coatings, a reactive emulsifier containing phosphate groups can be integrated into the molecular chain during polymerization, which enhances the coating’s compactness and corrosion resistance. This work focuses on the synthesis of styrene-butyl acrylate (St-BA) latex and methyl methacrylate-butyl acrylate (MMA-BA) latex using the reactive phosphate emulsifier ANPEO₁₀-P₁ through seed emulsion polymerization, achieving a conversion rate of approximately 99% and a solid content close to 50%. The resulting coatings from St-BA and MMA-BA latexes demonstrated long-term corrosion protection for carbon steel and aluminum alloy due to in-situ phosphatization, effectively preventing flash rust. Notably, the MMA-BA coating exhibited remarkable durability, enduring immersion for up to 1224 h (51 d) on Q235 carbon steel before reaching the failure threshold (∣Z∣_0.01Hz≤10⁶ Ω·cm²) on Q235 carbon steel. On 5052 aluminum alloy, the St-BA coating maintained ∣Z∣_0.01Hz>gt;10⁸ Ω·cm² for 480 h (20 d). Furthermore, the corrosion resistance of St-BA and MMA-BA coatings on Q235 steel sheet and 5052 aluminum alloy surpassed that of commercially available MMA-BA and St-BA coatings after immersion in a 3.5 wt% NaCl aqueous solution. This work also delves into the anticorrosion mechanism of MMA-BA and St-BA coatings.

Keywords

waterborne acrylic coating / in-situ phosphatization / emulsifier ANPEO₁₀-P₁ / flash rust / long-term corrosion protection

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