<p>Nickel–phosphorus–carbon nanotube (Ni–P–CNT) composite coatings demonstrate remarkable corrosion resistance and superior light absorption compared to conventional Ni–P coatings, making them highly suitable for solar absorber applications. This study explores the influence of CNT concentration (0–2.5&#xa0;g·L⁻¹) in the plating bath on the corrosion performance of aluminum substrates before and after a blackening process involving nitric acid etching to enhance solar absorption. The coatings were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical techniques such as open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Results revealed that CNT incorporation increased with concentration up to 2&#xa0;g·L⁻¹ but decreased at 2.5&#xa0;g·L⁻¹ due to agglomeration and particle precipitation. The optimal CNT loading of 1.5&#xa0;g·L⁻¹ produced the most uniform morphology, minimal etching, and the highest corrosion resistance after blackening, attributed to well-dispersed CNTs and reduced surface porosity. In contrast, higher CNT concentrations led to increased coating defects and porosity, accelerating etching and corrosion. Overall, a CNT concentration of 1.5&#xa0;g·L⁻¹ provided the best balance between corrosion protection and surface absorption efficiency, resulting in durable, high-performance coatings suitable for long-term solar energy applications.</p> Graphical abstract <p></p>