Alumina Thin Films

Nofz, Marianne

doi:10.1007/978-3-319-32101-1_133

Cited by 2 publications

(1 citation statement)

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“…Alumina coatings, prepared using the sol-gel method, have thicknesses between 10 nm to 10 µm depending on the composition of the sol, conditions of deposition, and the applied heat treatment [33]. Based on previous research using similar sol formulations deposited on P92 steels and heat treated at 650 • C, the alumina coating thickness formed on the steel was approximately 1 µm [34].…”

Section: Effect Of Coating Thicknessmentioning

confidence: 99%

Study of Al2O3 Sol-Gel Coatings on X20Cr13 in Artificial North German Basin Geothermal Water at 150 °C

et al. 2021

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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.

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Section: Effect Of Coating Thicknessmentioning

confidence: 99%