Optimizing aluminum alloy performance for marine superstructures: Advanced nanocomposite coating for enhanced corrosion resistance, flame retardancy, and mechanical strength

Aluminium alloys find applications in the marine industry for boat hulls, ship superstructures, and offshore structures due to their corrosion resistance in marine environments. Nanocomposites incorporating impermeable two-dimensional materials hold a particular interest in safeguarding metals against corrosion. The introduction of 3-(m-aminophenoxy)propyltrimethoxysilane (APPMS) functionalized hafnium nitride (HfN) into a coating matrix can enhance the barrier effect owing to its exceptional chemical and thermal stability. Integrating functionalized HfN into graphitic carbon nitride (GCN) within polyurethane (PU) leads to improved corrosion protection and fire-retardant properties. Through electrochemical techniques in chloride environments, the protective efficacy of aluminum coated with polyurethane containing varying concentrations of functionalized HfN/GCN was investigated. The resulting PU with functionalized HfN/GCN composite demonstrates superior flame-retardant capabilities, with significant reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. According to electrochemical impedance spectroscopy (EIS) measurements, PU/functionalized HfN/GCN exhibits enhanced coating resistance of 2.26×1010 Ω.cm2, even after 20 days of exposure to seawater. Featuring a water contact angle (WCA) of 161°, the newly developed PU/functionalized HfN/GCN coating displays exceptional water repellency. Moreover, PU/functionalized HfN/GCN demonstrates good mechanical properties in terms of adhesion strength and hardness within the PU substrate, enabling the coating to maintain its integrity even after prolonged immersion. The investigation presents a promising approach for developing advanced coatings tailored for marine applications, offering improved corrosion protection, fire resistance, water repellency, and mechanical durability. Thus, the PU/functionalized HfN/GCN nanocomposite shows promise as a viable coating component in marine applications.