Polyimide–polyurea copolymer coating with outstanding corrosion inhibition properties

ABSTRACT A novel class of copolymers containing polyimide and polyurea blocks with unique physical properties and capable of providing effective protection to aluminum alloy 2024‐T3 substrate against corrosion has been prepared. The structure and properties of polyurea‐ b ‐polyimide (PUI) copolymers were controlled by varying the co‐monomer concentration. The PUI block copolymer can reorganize into a supra‐molecular structure by forming intra‐ and inter‐hydrogen bonding interactions between adjacent copolymer chains, resulting in a dense and compact structure capable of protecting the imide ring from hydrolysis when exposed to a corrosive environment. Apart from minimized surface hydrolysis, the establishment of compacted morphology also leads to a drastically improved barrier property and reduced diffusivity. The corrosion rate and polarization resistances of PUI‐coated aluminum alloys were measured by using direct current polarization technique. Increasing polyurea concentration resulted in a remarkable decrease in diffussivity and surface energy, consistent with the measured remarkable increase in the coatings durability and corrosion performance. Corrosion inhibition tests were carried out for more than 30 weeks in a saturated NaCl solution containing 3.5 wt % of salt. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 45861.