Molecular design and copolymerization to enhance the anti-corrosion performance of waterborne acrylic coatings

•Acrylic-alkyd copolymers with distinct molecular structures are designed and synthesized to enhance corrosion resistance.•Acrylic-alkyd copolymer based waterborne coatings possess combined advantages of acrylic and alkyd resins.•Acrylic-alkyd copolymers enabled higher hydrophobicity and lower water diffusion coefficient.•EIS and immersion tests confirmed the enhanced corrosion resistance of acrylic-alkyd copolymers.•An approach to developing corrosion resistant waterborne coatings through molecular design is illustrated. Acrylic-alkyd copolymers with varied contents of the alkyd copolymer have been synthesized by free radical polymerization in order to create waterborne coatings with distinct molecular structures to enhance anti-corrosion performance. The acrylic-alkyd copolymers were found not only to possess combined advantages of acrylic and alkyd resins in coating properties such as stability, fast drying and hardness, but also to possess several properties required for enhanced corrosion resistance, especially a higher hydrophobicity of the coating surface, a lower water diffusion coefficient, and a denser network of copolymer films. The higher hydrophobicity of the coating surface was achieved through the design of acrylic-alkyd copolymers with acrylic branches and hydrophobic alkyd backbones, leading to increase in the water contact angles of the copolymer films. The denser coating network was achieved by the branched structure and the flexibility of the copolymer chains. This allows the copolymer particle stacking during the curing process and builds a denser barrier film with lower water diffusion coefficients. These coating properties have led to significant enhancement in the corrosion resistance of these acrylic-alkyd copolymer films, which has been confirmed by the results from electrochemical impedance spectra (EIS) and corrosion exposure tests. This work also illustrates a successful approach to developing corrosion resistant waterborne coatings through the design of copolymers with distinct molecular structures.