pH-Responsive Smart Polymer Nanocomposites for Anti-Corrosive Coatings

Metallic corrosion under adverse marine and industrial conditions imposes gigantic financial burdens and risks worldwide. Conventional waterproofing waterborne epoxy has passive barrier protection, but is also inherently microporous, lacking intrinsic repair ability against mechanical damage and thus rapidly decays. This is a critical gap that this work tries to bridge by designing a new pH-responsive hybrid polymer nanocomposite by using polyethyleneimine-tannic acid-cerium functionalized boron nitrate nanosheets with chitosan-capped mesoporous silica particles loaded with corrosion inhibitors in a water-borne epoxy matrix. The synergistic structure will enhance passive barrier properties through tortuous pathways created by two-dimensional nanofillers and active self-healing by means of pH-dependent on-demand release of corrosion-inhibitors in reaction to local acidity created upon the onset of corrosion. The electrochemical impedance spectrophotometry had revealed that the hybrid nanocomposite coating had a very high impedance modulus of the low frequency (9.8109 ohms/cm 2) of 75 days at low concentration (3.5 wt%) of NaCl solution, which is more than two orders of magnitude greater than the pure waterborne epoxy. In addition, the artificially scribed samples exhibited high healing properties under prolonged salt spray environments and corrosion proceeded very slowly even after 100 days in salt spray. Simulations with the help of molecular dynamics have confirmed the presence of much lower diffusion coefficients of water, oxygen and chloride ions and lower fractional free volume. These results compose scalable, environmentally benignant next-generation intelligent anticorrosive coating that can combine superior long-term barrier performance with autonomous active healing with enormous potential to increase the service life in problematic settings.