<p>High-temperature coatings are gaining popularity for their effectiveness to protect the components at elevated temperatures and harsh environments, against hot corrosion. In this context, this study investigates the hot corrosion behavior of nickel–aluminum (NL) composite coatings reinforced with nanodiamonds (ND). The coatings were systematically exposed to 800&#xa0;°C for durations of 1 and 3&#xa0;days in a corrosive environment of Na₂SO₄–60&#xa0;pct V₂O₅ salt. ND-reinforced NL coatings exhibited superior hot corrosion resistance compared to the bare NL coating. Notably, the 1&#xa0;wt&#xa0;pct ND-reinforced NL (NL-1ND) coating demonstrated an 88.28&#xa0;pct reduction in weight gain compared to the pure NL coating. In addition, the NL-1ND coating showed 66.7&#xa0;pct less porosity than the bare NL coating. The improved hot corrosion resistance is attributed to the denser microstructure, the transition of ND from <i>sp</i>³ to <i>sp</i>², smaller crystallite size, and the formation of a uniform passivation layer on the NL-1ND coating. Furthermore, the NL-1ND coating exhibited minimal adhesion strength reduction (5.4&#xa0;pct) after hot corrosion, significantly lower than the NL coating (33.3&#xa0;pct), highlighting its superior adhesion retention. These findings underscore the effectiveness of ND as a reinforcement material in significantly enhancing the hot corrosion resistance of NL coatings under severe thermal conditions.</p> Graphical Abstract <p></p>