Effects of inorganic sealant and brief heat treatments on corrosion behavior of plasma sprayed Cr2O3–Al2O3 composite ceramic coatings

• Corrosion behavior of plasma sprayed Cr2O3–Al2O3 coatings was investigated.
• Aluminum phosphate with nanoparticles was fabricated as high-temperature sealant.
• Brief-time heat treatments at 600 °C were performed on unsealed and sealed coatings.
• Sealed coatings have enhanced corrosion resistance even after heat treatment.

In the present study, Cr2O3–Al2O3 composite coatings were fabricated by atmospheric plasma spraying (APS) technique. Aluminum phosphate with small fraction of Al2O3 nanoparticles was applied as high-temperature sealant to enhance the anti-corrosion performance of the coatings. The inorganic sealant significantly reduced the open pore of the as-sprayed coatings and showed low shrinkage after heat treatment (600 °C, 30 min). Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and salt spray tests were used to assess anti-corrosive characteristics of the coatings. The sealants resulted in an augment of corrosion resistance properties of the coatings both before and after heat treatment, indicating effective sealing and good high temperature applicability. The sealed Cr2O3–Al2O3 composite coatings have a potential use in severe corrosion condition.

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