Study of Al2O3 Sol-Gel Coatings on X20Cr13 in Artificial North German Basin Geothermal Water at 150 °C
Autor: | Le Quynh Hoa, Regine Sojref, Ralph Bäßler, Gabriela Aristia, Marianne Nofz |
---|---|
Jazyk: | angličtina |
Rok vydání: | 2021 |
Předmět: |
Boehmite
Materials science 020209 energy Thermal resistance 02 engineering and technology Electrolyte engineering.material Corrosion Coating geothermal 0202 electrical engineering electronic engineering information engineering Materials Chemistry Sol-gel Al2O3 Surfaces and Interfaces 021001 nanoscience & nanotechnology Engineering (General). Civil engineering (General) Surfaces Coatings and Films Dielectric spectroscopy Chemical engineering engineering boehmite martensitic steels TA1-2040 0210 nano-technology Layer (electronics) |
Zdroj: | Coatings, Vol 11, Iss 526, p 526 (2021) Coatings Volume 11 Issue 5 |
ISSN: | 2079-6412 |
Popis: | Al2O3 has been widely used as a coating in industrial applications due to its excellent chemical and thermal resistance. Considering high temperatures and aggressive mediums exist in geothermal systems, Al2O3 can be a potential coating candidate to protect steels in geothermal applications. In this study, γ-Al2O3 was used as a coating on martensitic steels by applying AlOOH sol followed by a heat treatment at 600 °C. To evaluate the coating application process, one-, two-, and three-layer coatings were tested in the artificial North German Basin (NGB), containing 166 g/L Cl−, at 150 °C and 1 MPa for 168 h. To reveal the stability of the Al2O3 coating in NGB solution, three-layer coatings were used in exposure tests for 24, 168, 672, and 1296 h, followed by surface and cross-section characterization. SEM images show that the Al2O3 coating was stable up to 1296 h of exposure, where the outer layer mostly transformed into boehmite AlOOH with needle-like crystals dominating the surface. Closer analysis of cross-sections showed that the interface between each layer was affected in long-term exposure tests, which caused local delamination after 168 h of exposure. In separate experiments, electrochemical impedance spectroscopy (EIS) was performed at 150 °C to evaluate the changes of coatings within the first 24 h. Results showed that the most significant decrease in the impedance is within 6 h, which can be associated with the electrolyte penetration through the coating, followed by the formation of AlOOH. Here, results of both short-term EIS measurements (up to 24 h) and long-term exposure tests (up to 1296 h) are discussed. |
Databáze: | OpenAIRE |
Externí odkaz: |