resumo
Amorphous plasma electrolytic oxidation (PEO) coating with sealed discharge channels can be formed in alkaline phosphate electrolyte containing montmorillonite clay particles. The effect of various concentrations of phosphate and hydroxide ions in the clay-containing electrolyte on the microstructure of the coatings was studied in the present work and correlated with the corrosion behavior. The clay particles were reactively incorporated into the coating. Single amorphous phase appears in PEO coatings produced from electrolytes containing higher concentration of phosphate. These amorphous coatings are degrading within a relatively short period in 0.5 wt% NaCl solution. Electrolytes containing higher concentration of KOH tend to produce mixed PEO coatings composed of crystalline and amorphous phases. These layers demonstrate higher corrosion resistance and degradation stability. Thus, the degradation rate of PEO coatings is governed mostly by the stability of their phase composition, which might be controlled by varying electrolyte composition. (C) 2014 Elsevier B.V. All rights reserved.
palavras-chave
SOL-GEL COATINGS; CORROSION-RESISTANCE; MG ALLOY; OXIDATION; AZ91D; PHOSPHATE; FILMS; PERFORMANCE; PROTECTION; AA2024-T3
categoria
Materials Science; Physics
autores
Lu, XP; Sah, SP; Scharnagl, N; Stormer, M; Starykevich, M; Mohedano, M; Blawert, C; Zheludkevich, ML; Kainer, KU
nossos autores
agradecimentos
The technical support of Mr. Volker Heitmann and Mr. Ulrich Burmester during the course of this work is gratefully acknowledged. X. Lu thanks China Scholarship Council for the award of fellowship and funding. M. Mohedano is grateful to the Alexander von Humboldt Foundation, Germany, for the award of AvH research fellowship and financial assistance.