Enhancing corrosion resistance of waterborne polyurethanes by incorporation of side-chain-ester engineered vegetable oil diols

Vegetable oil-based waterborne polyurethanes (WPUs) demonstrate significant potential as eco-friendly anticorrosion coatings due to their hydrophobic aliphatic chains. However, the hydrolysis susceptibility of backbone-incorporated ester groups inherently derived from vegetable oil structures has been consistently overlooked in corrosion protection enhancement. Herein, we developed structurally engineered diols with side-chain-ester groups, which were systematically incorporated (0–100 %) into WPUs as replacements for petroleum-based polyester glycol, with successful synthesis confirmed by FTIR and SEM-EDS characterization. The emulsions' average particle size (increasing from 25.0 to 137.3 nm), water tolerance (water contact angle increasing from 59.1° to 80.3° with absorption decreasing from 136 % to 31 %), and chemical resistance (i corr decreasing from 1.53 × 10 −6 to 5.79 × 10 −8 A cm −2 ) of WPUs were all enhanced by the diols' incorporation. Crucially, side-chain-ester WPUs exhibit superior corrosion resistance versus castor oil-based WPUs (backbone-esters), maintaining structural/spectral stability after 24 h alkaline treatment, while castor oil films degrade (FTIR peak attenuation) and polyester glycol controls fail completely. This work establishes side-chain ester relocation as an innovative molecular design strategy to significantly enhance the corrosion resistance of vegetable oil-based coatings.