Comparison of plasma electrolytic oxidation of zirconium alloy in silicate- and aluminate-based electrolytes and wear properties of the resulting coatings

• Published in: Electrochimica acta 2012-12, Vol.85, p.25-32
• Main Authors: Cheng, Yingliang, Wu, Fan, Dong, Jiali, Wu, Xiangquan, Xue, Zhigang, Matykina, E., Skeldon, P., Thompson, G.E.
• Format: Article
• Language: English
• Subjects: Aluminates; Aluminum; Chemistry; Coatings; Dissolution; Dry sliding test; Electrochemistry; Electrolytes; Exact sciences and technology; General and physical chemistry; Oxidation; Plasma electrolytic oxidation; Silicates; t-ZrO2; Zirconium; Zirconium base alloys
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2012.08.110

[Display omitted] ► PEO processes in silicate and aluminate electrolytes are compared for Zircaloy-2. ► Significant different behaviors are observed for the PEO in the two electrolytes. ► Superior wear resistance was observed for the coating from aluminate electrolyte. ► The coatings from aluminate electrolyte possess much higher t-ZrO2 content. ► The results show that Al2O3 is a more efficient tetragonal ZrO2 stabilizer. Plasma electrolytic oxidation of Zircaloy-2 at constant rms current is examined in silicate and aluminate electrolytes, revealing significantly different behaviors in the growth kinetics and properties of the coatings. Coatings thicken continuously in the silicate electrolyte, while in the aluminate electrolyte, the thickness reaches a relatively constant value. The latter coincides with changing appearances of discharges and detachment of an outer coating layer. Dissolution of zirconium is faster in the silicate electrolyte in the early stage of PEO, but is faster in the aluminate electrolyte following coating breakdown. The pre-spallation coating formed in the aluminate electrolyte shows superior wear resistance, which can be ascribed to its relative compactness, associated with the presence of tetragonal zirconia stabilized by aluminium species.