Kinetics investigation of alumina ceramics corrosion in nitric acid

ABSTRACT

The most widely used ceramic material is aluminium oxide, known as alumina. Due to its superior properties such as chemical stability, high wear resistance, refractoriness and so on, it is ideal for applications in aggressive environment. This type of environment often includes exposure to corrosive solids, liquids and gases. When ceramics come in contact with corrosive medium, several corrosion mechanisms can occur, depending on a number of parameters. Therefore, the corrosion behaviour of cold isostatically pressed (CIP) high purity alumina ceramics was observed under different conditions: 0.5, 1.25 and 2 mol dm⁻³ of nitric acid at 25°C, 40°C and 55°C through 10 days. Purity of used alumina ceramics was 99.8345 wt. % with 0.1655 wt. % of both sintering aid (MgO) and impurities (SiO₂, CaO, Na₂O and Fe₂O₃). The results show that Al₂O₃ ceramics exhibit good corrosion resistance in nitric acid. Al₂O₃ corrosion behaviour varies depending on the temperature, time and HNO₃ concentration. In view of the reaction kinetics, it proceeds in the near-parabolic law in HNO₃ aqueous solution and decreases with an increase of the HNO₃ concentration.

KEYWORDS:

• Alumina
• corrosion activation energy
• corrosion rate

Acknowledgements

The authors would like to thank Ivan Nemet (Laboratory of Analytical Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Croatia) for ICP-AES measurements. The authors would also like to thank Matt Sertić and Tomislav Jurašinović from Applied Ceramics, Inc. for green and hard machining alumina ceramics samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financed by the Croatian Science Foundation within the project Monolithic and composite advanced ceramics for wear and corrosion protection (WECOR) (IP-2016-06-6000).