Publisher : The Korean Institute of Surface Engineering
DOI : 10.5695/JKISE.2016.49.3.280
Title & Authors
Influences of Potassium Fluoride (KF) Addition on the Surface Characteristics in Plasma Electrolytic Oxidation of Marine Grade Al Alloy Lee, Jung-Hyung; Kim, Seong-Jong;
In this study, we investigated the influences of potassium fluoride(KF) addition on the surface characteristics of plasma electrolytic oxidation(PEO) coating produced on Al alloy. The PEO of marine grade Al alloy(5083 grade) was conducted in KOH 1g/L solution adding different concentrations of KF(0, 1 and 2 g/L) under a galvanostatic regime. With KF addition, unusual behavior was observed on the voltage-time characteristic curves, which can be characterized by the following process: (i) initial rapid increase in voltage (ii) a short plateau after 1st breakdown (iii) gradual increase in voltage (iv) intermittent fluctuation of voltage after 2nd breakdown. The SEM observation revealed irregular surface morphology with KF addition, as compared with one formed without KF addition, which had a reticulate structure. The XRD analysis detected the formation of aluminium hydroxide fluoride hydrate() on surface grown by PEO process with KF. Particularly, at very early stage of the process (~ 120 s), thin film was formed having nanoporous structure, and F element was confirmed on surface by EDS analysis. The thickness and surface roughness of the coating increased with increasing KF concentration. As a result, KF addition was found to be less beneficial influences on PEO of marine grade Al alloy, and therefore needs further research to improve its capability.
K. Wang, B. Koo, C. Lee, Y. Kim, S. Lee, E. Byon, Characteristics of oxide layers formed on Al2021 alloys by plasma electrolytic oxidation in aluminate fluorosilicate electrolyte, J. Korean Inst. Surf. Eng., 41 (2008) 308-311.
J. Lee, S. Kim, Characterization of Ceramic Oxide Layer Produced on Commercial Al Alloy by Plasma Electrolytic Oxidation in Various KOH Concentrations, J. Korean Inst. Surf. Eng., 49 (2016) 119-124.
S. Ikonopisov, Theory of electrical breakdown during formation of barrier anodic films, Electrochim. Acta, 22 (1977) 1077-1082.
V. S. Rudnev, Multiphase anodic layers and prospects of their application, Prot. Met., 44 (2008) 263-272.
B. Kazanski, A. Kossenko, M. Zinigrad, A. Lugovskoy, Fluoride ions as modifiers of the oxide layer produced by plasma electrolytic oxidation on AZ91D magnesium alloy, Appl. Surf. Sci., 287 (2013) 461-466.
J. Liang, B. Guo, J. Tian, H. Liu, J. Zhou, T. Xu, Effect of potassium fluoride in electrolytic solution on the structure and properties of microarc oxidation coatings on magnesium alloy, Appl. Surf. Sci., 252 (2005) 345-351.
I. C. Cheng, E. G. Fu, L. D. Liu, C. Y. Lee, C. S. Lin, Effect of Fluorine Anions on Anodizing Behavior of AZ91 Magnesium Alloy in Alkaline Solutions, J. Electrochem. Soc., 155 (2008) C219-C225.
L. Wang, L. Chen, Z. Yan, H. Wang, J. Peng, Effect of potassium fluoride on structure and corrosion resistance of plasma electrolytic oxidation films formed on AZ31 magnesium alloy, J. Alloy Compd., 480 (2009) 469-474.
B. Kazanski, A. Kossenko, A. Lugovskoy, M. Zinigrad, Fluoride Influence on the Properties of Oxide Layer Produced by Plasma Electrolytic Oxidation, Defect Diffus. Forum, 326-328 (2012) 498-503.
J. Lee, S. Kim, Influence of $Na_2SiO_3$ addition on surface microstructure and cavitation damage characteristics for plasma electrolytic oxidation of Al-Mg alloy, Jpn. J. Appl. Phys., 55 (2016) 01AF02-1-01AF02-5.
L. O. Snizhko , A. L. Yerokhin, A. Pilkington, N. L. Gurevina, D. O. Misnyankin, A. Leyland, A. Matthews, Anodic processes in plasma electrolytic oxidation of aluminium in alkaline solutions, Electrochim. Acta, 49 (2004) 2085-2095.
J. A. Curran, T. W. Clyne, Porosity in plasma electrolytic oxide coatings, Acta Mater., 54 (2006) 1985-1993.
P. S. Santos, H. S. Santos, S. P. Toledo, Standard transition aluminas. electron microscopy studies, Mater. Res., 3 (2000) 104-114.
T. H. Teh, A. Berkani, S. Mato, P. Skeldon, G. E. Thompson, H. Habazaki, K. Shimizu, Initial stages of plasma electrolytic oxidation of titanium, Corros. Sci., 45 (2003) 2757-2768.
C. Kim, J. Choi, H. Kim, D. Lee, C. Hyun, S. Nam, Effects of interlayer roughness on deposition rate and morphology of aerosol-deposited $Al_2O_3$ thick films, Ceram. Int., 38 (2012) 5621-5627.