This study investigates carbon nanotube (CNT)-reinforced alumina fly ash (FA) coatings, namely AF (unreinforced), 1CAF (with 1 wt% CNT), and 2CAF (with 2 wt% CNT), on marine-grade steel. Microstructural analysis shows 1CAF coatings denser by ∼15.32% due to CNT reinforcement, while 2CAF coatings display ∼9.68% increased porosity from CNT agglomeration. Raman spectroscopy confirms CNT retention. 1CAF coatings exhibit ∼14.66% higher microhardness, ∼15.96% higher adhesion strength, and ∼15.66% improved fracture toughness compared to AF coatings, attributed to pore sealing through CNT reinforcement. Enhanced erosion resistance (∼14.59%) in 1CAF coatings was observed due to improved mechanical properties and CNTs mitigating crack propagation. Validation through an artificial neural network (ANN) modeling and regression analysis supports 1CAF coatings’ promise for harsh marine environments, offering enhanced durability.