A Phosphate-Modified Aqueous Acrylic-Alkyd Resin for Corrosion Protection of Iron Substrates

Purpose：HEMAP was used to chelate iron ions and form a passivation layer while also increasing crosslink density and adhesion in a waterborne acrylic-alkyd resin for iron protection.

System and methods：Acrylic-alkyd copolymers with different HEMAP contents were synthesized by free-radical polymerization. Adhesion, crosslinking, barrier behavior and electrochemical corrosion resistance on iron substrates were compared to identify an effective dosage.

Key findings and mechanism：Different HEMAP levels were incorporated into a waterborne acrylic-alkyd copolymer by free-radical polymerization. Electrochemical tests showed that HEMAP increased crosslink density and adhesion and reduced penetration of corrosive species, with 2 wt% HEMAP giving the clearest improvement on iron. Phosphate groups can chelate iron ions or support a passivation layer while strengthening the resin-metal interface. Higher crosslink density further limits water, oxygen and ion transport, combining chemical passivation with a physical barrier rather than relying only on corrosion inhibitors.

Application value and limits：The system combines chemical chelation with crosslinked barrier protection for waterborne metal coatings. Phosphate content, cure level and hydrolytic stability should be optimized together. The 2 wt% result is specific to this resin and electrochemical test set. Phosphate may interact with metal driers, amine neutralizers or alkaline pigments in waterborne alkyds, so storage stability, drying time and long-term corrosion performance must be verified.