Mass Transfer of Phosphorus-Containing Corrosion Inhibitors in Epoxy Protective Coatings

Mass transfer of phosphorus-containing corrosion inhibitors in epoxy matrices, which form the layers of anticorrosion primers and coatings, has been investigated. It has been shown that diffusion profiles of phosphonic acid distribution are stepwise, which has been previously observed in a broad range of mineral and organic acids. Penetration rate constants λ of phosphonic acids are comparable with the values that are intrinsic for inorganic acids. The acid-to-water ratio in internal solution in polymer is higher than in outer diffusant solution upon diffusion of phosphonic acids to amine-hardened epoxy matrices. A selective diffusion of phosphate anions has been observed in the solutions of acidic monosubstituted phosphates.