Publication Type Journal Article
Title Characterization of Porous Phosphate Coatings Enriched with Magnesium or Zinc on CP Titanium Grade 2 under DC Plasma Electrolytic Oxidation
Authors Krzysztof Rokosz Tadeusz Hryniewicz Sofia Gaiaschi Patrick Chapon Steinar Raaen Kornel Pietrzak Winfried Malorny JCS Fernandes
Groups CSSE
Journal METALS
Year 2018
Month February
Volume 8
Number 2
Pages
Abstract The aim of the paper is to study and determine the effect of voltage increasing from 500 up to 650 V-DC on chemical and electrochemical properties of the obtained porous coatings with plasma electrolytic oxidation (PEO) processes, known also as micro arc oxidation (MAO). In the present paper, the chemical and electrochemical characterization of porous phosphate coatings enriched with magnesium or zinc on commercially pure (CP) Titanium Grade 2 under DC-PEO obtained in electrolytes based on concentrated 85\% analytically pure H3PO4 (98 g/mole) acid with additions of 500 gL(-1) of zinc nitrate Zn(NO3)(2)center dot 6H(2)O or magnesium nitrate Mg(NO3)(2)center dot 6H(2)O, are described. These materials were characterized using scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES). It was found that the voltage of PEO process has influence on the chemical composition and thickness of the obtained porous coatings as well as on their electrochemical behavior. The higher the potential of PEO treatment, the higher the amount of zinc-to-phosphorus ratio for zinc enriched coatings was obtained, whereas in magnesium enriched coatings, the average amount of magnesium detected in PEO coating is approximately independent of the PEO voltages. Based on XPS studies, it was found out that most likely the top 10 nm of porous coatings is constructed of titanium (Ti4+), magnesium (Mg2+), zinc (Zn2+), and phosphates PO43- and/or HPO42- and/or H2PO4- and/or P2O74-. On the basis of GDOES studies, a four-sub-layer model of PEO coatings is proposed. Analysis of the potentiodynamic corrosion curves allowed to conclude that the best electrochemical repeatability was noted for magnesium and zinc enriched coatings obtained at 575 V-DC.
DOI http://dx.doi.org/10.3390/met8020112
ISBN
Publisher
Book Title
ISSN 2075-4701
EISSN
Conference Name
Bibtex ID ISI:000427530700032
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