Enhancement of high-temperature stability of solar absorber coatings on metallic substrates through diffusion barriers

The high-temperature stability of solar absorber paints is critical for the efficiency of concentrating solar power systems, particularly central towers operating at ∼800 °C, where ion interdiffusion at the coating/substrate interface is significant. This work examines the effect of a diffusion barrier (DB) formed by controlled surface oxidation of stainless steel 316L (SS316) and Inconel 625 (INC625) at 800 °C to improve the thermal stability and optical performance. A CrAlSiN/AlSiO solar absorber tandem structure was deposited on oxidized and unoxidized substrates, with their stability compared after annealing at 800 °C for 2 h. The presence of the DB layer resulted in improved thermal stability and optical performance, with post-annealing absorptance values of 0.953 (SS316) and 0.949 (INC625), surpassing those of the reference samples, without the diffusion barrier (0.932 and 0.901, respectively). Microstructural and spectroscopic analyses confirmed the effectiveness of the DB, highlighting its potential for advanced concentrating solar power applications. • Ion diffusion through substrate interface is mitigated by the diffusion barrier (DB). • DB layer improves thermal stability in air after annealing (800 °C/2 h). • Controlled oxidation of substrates enhances optical efficiency of SACs. • CrAlSiN/AlSiO tandem coatings grown on DB increase the absorptance values by 2–5 %.