Infrared-responsive shape memory self-healing and fluorescent damage-indication anti-corrosion coatings for aluminum alloys

Widely applied aluminum alloys in ship hulls, underwater vehicles, and marine machinery experience severe corrosion in harsh marine environments. For corrosion protection of aluminum alloys, the most convenient, effective, and low-cost approach was the application of anti-corrosion coatings. Coatings possessing self-healing properties to spontaneously repair damages have emerged as a research focus for new types of coatings. In this study, focused on the indication and repair of anti-corrosion coating damages for aluminum alloys, the fluorescent aggregation-induced emission (AIE) composite probe, rhodamine-naphthalimide (RNI), was synthesized, and the composite polymer materials HPPA-SMPU containing 2-hydroxyphosphinoyl carboxylic acid-doped polyaniline and shape memory polyurethane were prepared. Coaxial electrospinning technology was introduced to combine the two and create the fibrous materials with the fiber wall constructed from HPPA-SMPU, encapsulating the interior RNI solution. The fibers were incorporated into the epoxy coatings. RNI exhibited water-triggered AIE, Al³⁺-CHEF (chelation-enhanced fluorescence), and pH-responsive fluorescent properties to indicate infrared laser-targeted points of coating damages. The photothermal properties of HPPA-SMPU caused localized heating of the damaged coatings, reaching the phase transition temperature of epoxy and SMPU, leading to softening, expansion, shape memory behavior, and healing of the coating damages. The self-healing approaches enhanced the protective performance of the coatings for aluminum alloys, showcasing and extending the development of synergistic and intelligent functions in novel self-healing coating technologies.