Phosphate Coatings Enriched with Copper on Titanium Substrate Fabricated Via DC-PEO Process.

Krzysztof Rokosz,Dalibor Matýsek,Wojciech Kacalak,Sofia Gaiaschi,Katarzyna Tandecka,Łukasz Dudek,Tadeusz Hryniewicz,Kornel Pietrzak,Winfried Malorny,Patrick Chapon,Steinar Raaen

doi:10.3390/ma13061295

Abstract

The present paper covers the possible ways to fabricate advanced porous coatings that are enriched in copper on a titanium substrate through Direct Current Plasma Electrolytic Oxidation (DC-PEO) with voltage control, in electrolytes made of concentrated orthophosphoric acid with the addition of copper(II) nitrate(V) trihydrate. In these studies, solutions containing from 0 to 650 g salt per 1 dm3 of acid and anodic voltages from 450 V up to 650 V were used. The obtained coatings featuring variable porosity could be best defined by the three-dimensional (3D) parameter Sz, which lies in the range 9.72 to 45.18 μm. The use of copper(II) nitrate(V) trihydrate in the electrolyte, resulted, for all cases, in the incorporation of the two oxidation forms, i.e., Cu+ and Cu2+ into the coatings. Detailed X-Ray Photoelectron Spectroscopy (XPS) studies layers allowed for stating that the percentage of copper in the surface layer of the obtained coatings was in the range of 0.24 at% to 2.59 at%. The X-Ray Diffraction (XRD) studies showed the presence of copper (α-Cu2P2O7, and Cu3(PO4)2) and titanium (TiO2-anatase, TiO3, TiP2O7, and Ti0.73O0.91) compounds in coatings. From Energy-Dispersive X-Ray Spectroscopy (EDS) and XPS studies, it was found that the Cu/P ratio increases with the increase of voltage and the amount of salt in the electrolyte. The depth profile analysis by Glow-Discharge Optical Emission Spectroscopy (GDOES) method showed that a three-layer model consisting of a top porous layer, a semi-porous layer, and a transient/barrier layer might describe the fabricated coatings.

Highlights

The Plasma Electrolytic Oxidation (PEO) process, which is known under the name of MicroArc Oxidation (MAO), is used to fabricate porous coatings on light metals substrates, such as titanium and its alloys
Its alloys [2,3], which are enriched with selected chemical elements, during the PEO processes under both Direct Current (DC) [1,2,3] or Alternating Current (AC) [4] voltage conditions in electrolytes that are based on orthophosphoric acid
It has to be pointed out that additional antibacterial protection can be obtained by fabrication of PEO coatings in solutions mostly containing silver or copper ions, which may be obtained by the use of CH3 COOAg [5] or Cu(CH3 COO)2 [6], respectively

Summary

Introduction

Arc Oxidation (MAO), is used to fabricate porous coatings on light metals substrates, such as titanium and its alloys. Materials 2020, 13, 1295 because of their chemical composition They are interesting background substrates for catalysts. Its alloys [2,3], which are enriched with selected chemical elements, during the PEO processes under both Direct Current (DC) [1,2,3] or Alternating Current (AC) [4] voltage conditions in electrolytes that are based on orthophosphoric acid. It has to be pointed out that additional antibacterial protection can be obtained by fabrication of PEO coatings in solutions mostly containing silver or copper ions, which may be obtained by the use of CH3 COOAg [5] or Cu(CH3 COO)2 [6], respectively

Results

Discussion

Conclusion