In the present study, a novel protective thermal barrier coating was developed. Amorphous aluminum phosphate powder was synthesized by sol–gel process and applied on Inconel 625 by air plasma spray (APS). Thermal conductivity of the compound was determined using laser flash analysis (LFA). The adhesion strength of the coating was evaluated by tensile test according to the ASTM-C633 standard. Hot corrosion behavior of the coatings was examined in Na2SO4–10 wt% NaCl molten salt at 1100 °C for 100 h. Thermal conductivity of the compound was obtained to be 1.1–2.2 W m−1 K−1 at 20–1000 °C which was considerably a low value compared to conventional TBC (8YSZ). The adhesion strength of the coating was obtained to be 40.8 ± 2 MPa which would be a significant value considering the applying method. The parabolic rate constant (Kp) for the coated sample was 23 times lower than that of the bare one after 100 h of exposure time.

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