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Plasma Electrolytic Oxidation (PEO) known also as Micro Arc Oxidation (MAO) process is widely used to fabricate porous coatings on titanium and its alloys mainly in water- and acid-based solutions to different applications, e.g. in biomaterials, catalysts, and sensors. In the present paper, the SEM, EDS, and XPS results of porous coatings obtained by PEO treatment on titanium in electrolytes based on concentrated phosphoric H3PO4 acid with calcium nitrate tetrahydrate Ca(NO3)2·4H2O, or magnesium nitrate hexahydrate Mg(NO3)2·6H2O, or zinc nitrate hexahydrate Zn(NO3)2·6H2O for 3 minutes at 200 Vpp (peak to peak) with frequency of 50 Hz, are presented. Based on EDS results, the Ca/P, Mg/P, and Zn/P ratios, which equal to 0.95, 0.176, and 0.231, respectively, were found out. The XPS studies of the top 10 nm of the porous layer clearly indicate that it contains mainly phosphates (PO4 3- and/or HPO4 2- and/or H2PO4 -, and/or P2O7 4-) with titanium (Ti4+) and calcium (Ca2+) or magnesium (Mg2+), or zinc (Zn2+). [ABSTRACT FROM AUTHOR]

The purpose of this work is to produce and characterize (chemical composition and roughness parameters) porous coatings enriched in calcium and phosphorus on the titanium (CP Titanium Grade 2) by plasma electrolytic oxidation. As an electrolyte, a mixture of phosphoric acid H3PO4 and calcium nitrate Ca(NO3)2·4H2O was used. Based on obtained EDS and roughness results of PEO coatings, the effect of PEO voltages on the chemical composition and surface roughness of porous coatings was determined. With voltage increasing from 450 V to 650 V, the calcium in PEO coatings obtained in freshly prepared electrolyte was also found to increase. In addition, the Ca/P ratio increased linearly with voltage increasing according to the formula Ca/P = 0.035·U+0.176 (by wt%) and Ca/P = 0.03·U+0.13 (by at%). It was also noticed that the surface roughness increases with the voltage increasing, what is related to the change in coating porosity, i.e. the higher is the surface roughness, the bigger are pores sizes obtained. [ABSTRACT FROM AUTHOR]

The SEM and EDS results of porous coatings formed on pure titanium by Plasma Electrolytic Oxidation (Micro Arc Oxidation) under DC regime of voltage in the electrolytes containing of 500 g zinc nitrate Zn(NO3)2·6H2O in 1000 mL of concentrated phosphoric acid H3PO4 at three voltages, i.e. 450 V, 550 V, 650 V for 3 minutes, are presented. The PEO coatings with pores, which have different shapes and the diameters, consist mainly of phosphorus, titanium and zinc. The maximum of zinc-to-phosphorus (Zn/P) ratio was found for treatment at 650 V and it equals 0.43 (wt%) | 0.20 (at%), while the minimum of that coefficient was recorded for the voltage of 450 V and equaling 0.26 (wt%) | 0.12 (at%). Performed studies have shown a possible way to form the porous coatings enriched with zinc by Plasma Electrolytic Oxidation in electrolyte containing concentrated phosphoric acid H3PO4 with zinc nitrate Zn(NO3)2·6H2O. [ABSTRACT FROM AUTHOR]

The SEM and EDS study results of coatings obtained on titanium by Plasma Electrolytic Oxidation (PEO) in the electrolytes containing of 600 g copper nitrate in 1 liter of concentrated phosphoric acid at 450 V for 1 and 3 minutes, are presented. The obtained coatings are porous and consist mainly of phosphorus within titanium and copper. It was found that the time of PEO oxidation has impact on the chemical composition of the coatings. The longer time of PEO treatment, the higher amount of copper inside coating. The PEO oxidation of titanium for 1 minute has resulted in the creation of coating, on which 3 phases where found, which contained up to 13.4 wt% (9 at%) of copper inside the phosphate structure. In case of 1 minute PEO treatment of titanium, the 2 phases were found, which contained up to 13 wt% (8 at%) of copper inside the phosphate structure. The copper-tophosphorus ratios after 1 minute processing belong to the range from 0.28 by wt% (0.14 by at%) to 0.47 by wt% (0.23 by at%), while after 3 minutes the same ratios belong to the range from 0.27 by wt% (0.13 by at%) to 0.35 by wt% (0.17 by at%). In summary, it should be stated that the higher amounts of phosphorus and copper were recorded on titanium after PEO oxidation for 3 minutes than these after 1 minute. [ABSTRACT FROM AUTHOR]

The SEM and EDS results of coatings obtained on pure niobium and titanium alloys (NiTi and Ti6Al4V) by Plasma Electrolytic Oxidation in the electrolytes containing of 300 g and 600 g copper nitrate in 1 litre of concentrated phosphoric acid at 450 V for 3 minutes, are presented. The obtained coatings are porous and consist mainly of phosphorus within titanium and copper. For each coating, the Cu/P ratios were calculated. The maximum of that coefficient was found for niobium and Ti6Al4V alloy oxidised in the electrolyte containing 600 g of Cu(NO3)2 in 1 dm3 of H3PO4 and equaling to 0.22 (wt%) | 0.11 (at%). The minimum of Cu/P ratio was recorded for NiTi and Ti6Al4V alloys oxidised by PEO in electrolyte consisting of 300 g of copper nitrate in 1 dm3 of concentrated phosphoric acid and equals to 0.12 (wt%) | 0.06 (at%). The middle value of that ratio was recorded for NiTi and it equals to 0.16 (wt%) | 0.08 (at%). [ABSTRACT FROM AUTHOR]

In the paper, the surface layers formed on nickel-titanium alloy during Plasma Electrolytic Oxidation (PEO), known also as Micro Arc Oxidation (MAO), are described. The mixture of phosphoric acid and copper nitrate as the electrolyte for all plasma electrochemical processes was used. Nitinol biomaterial was used for the studies. All the experiments were performed under the voltage of 450 V and current density of 0.3 A/dm2. The main purpose of the studies was to achieve the highest amount of copper in the surface layer versus amount of the copper nitrate in phosphoric acid. The highest copper concentration was found in the surface layer after the PEO treatment in the electrolyte consisting of 150g Cu(NO3)2 in 0.5 dm3 H3PO4. The worst results, in case of the amount of copper in the NiTi surface layer, were recorded after oxidizing in the solution with 5 g Cu(NO3)2. [ABSTRACT FROM AUTHOR]

In the paper, the passive surface layers of AISI 304L after standard (EP50) and very-high-current density electropolishing (EP1000) in a mixture of orthophosphoric and sulfuric acids in a 1:4 ratio, are presented. The main finding of the presented studies is enrichment of the steel surface film in chromium: total chromium to total iron ratio was equal to 6.6 after EP50 and to 2.8 after EP1000; on the other hand, chromium compounds to iron compounds ratio was equal to 10.1 after EP50, and 3.9 after EP1000. [ABSTRACT FROM AUTHOR]

This work presents the nanoindentation results of two newly developed titanium alloy biomaterials, TNZ and Ti2448, after different surface treatments. The investigations were performed on the samples, AR - as received, MP - after abrasive polishing, EP - after a standard electropolshing, and MEP - after magnetoelectropolishing. The electropolishing processes, both EP and MEP, were conducted in the same proprietary electrolyte based on concentrated sulfuric acid. The mechanical properties of the titanium alloys biomaterials demonstrated an evident dependence on the surface treatment method, with MEP samples revealing extremely different behaviour and mechanical properties. Such a different mechanical behaviour may mean completely different composition and thickness of the surface film formed on the studied samples after MEP [ABSTRACT FROM AUTHOR]

The paper presents the study results on chemical composition of the coarse primary M7C3 carbides occurring in the soft annealed NC11LV/D2 tool steel consisting of: 1.53% C; 11.65% Cr; 0.01% W; 0.81% Mo; 0.068% V; (balance iron plus admixtures), used for cold operation. The microanalyzer of type SEMPROBE Su-30, French made by CAMECA Co., equipped with two WDS X-ray spectrometers and an EDS VOYAGER 3 100, NORAN Instruments Co., made in USA. It was found that out of the three alloying elements occurring in the big carbides of the annealed NC11LV/D2 steel, i.e. Cr, Mo, and V, the chromium appears to be the most uniformly distributed. The big carbides vary concerning C, Cr, Mo, V; the greatest differentiation degree of the contents of Mo and Cr, and the least - of vanadium. The average chemical composition of the big/coarse carbides is as follows: C = 9.42±1.28%; Cr = 44.17±2.95%; Mo = 4.48±3.52%; V = 4.53±0.31%; balance Fe. [ABSTRACT FROM AUTHOR]

In the paper, there are presented the analyses of iron Fe2p3/2 and chromium Cr2p3/2 and oxide O1s XPS spectra of surfaces obtained after abrasive and electrochemical polishing with additional treatment as chemical chelating in the solution containing of 10% Citric Acid and 2% Ethylenediaminetetraacetic Acid. There was also performed electro-chelating after mechanical polishing in the electrolyte for chemical chelating. The maximum values of chromium compounds to iron compounds ratio were obtained after electropolishing with and without stirring with chemical chelating in Citric Acid and EDTA and they were in rage from 3.5 to 3.6. The minimum value was obtained for the steel surface after abrasive polishing and electro-chelating and was equal 1.3. After electrochemical polishing and chemical passivation in the surface layer there were detected FeO and Cr(OH)3 as dominated compounds. After abrasive polishing and electro-chelating there were mostly Fe2O3 and Cr2O3. [ABSTRACT FROM AUTHOR]

Electropolishing is the electrolytic metal finishing process currently widely used in several high tech applications such as cardiovascular and orthopaedic body implants, pharmaceutical and semiconductor installations, superconductive niobium cavities, among others. The process provides a very clean, smooth, Beilby layer free, corrosion resistant surface. Currently, almost any metal, alloy and intermetallic compound can be electropolished, but in spite of that, we still do not have a single commonly accepted electropolishing theory. To make it even more complicated, the electropolishing process is constantly modified by addition of other physical agents and/or forces such as a magnetic field - magnetoelectropolishing, ultrasounds, or by changing the existing process parameters such as switching from direct to pulse current. The existing electropolishing theories differ in many ways from each other but possess one common ingredient, namely the viscous layer. The aim of this work is to show that the viscous layer is not an indispensible prerequisite to achieve a satisfactory electropolishing finish in every metal-electrolyte system. A supplement to the most broadly accepted electropolishing solid film theory by Hoar, namely the enhanced oxidation-dissolution equilibrium theory, is proposed. [ABSTRACT FROM AUTHOR]

A new advanced technology is proposed to obtain bare metal surfaces for peripheral stents, endodontic files and another medical devices. The effect of an externally applied magnetic field during electropolishing (magnetoelectropolishing) of Nitinol on its surface properties was investigated. The results are compared with standard electropolished Nitinol in the same electrolyte under the same process conditions. To evaluate surface properties, the following techniques were used: SEM and EDX, AFM, contact angle measurement, Auger electron spectroscopy, electrochemical impedance spectroscopy and fatigue resistance testing. All of the above analyses showed significant differences between magnetoelectropolished and conventional electropolished Nitinol surfaces. The two most prominent differences, which are likely to have the most profound implications on increased use of this intermetallic material in medical application are improved wettability and fatigue resistance. [ABSTRACT FROM AUTHOR]

This paper aims to present the preliminary results of magnetoelectropolishing, a process derived and named by application of an external magnetic field coupled with the process being controlled and maintained under oxygen evolution to achieve an electropolished surface of a workpiece. The obtained surfaces exhibit reduced microroughness, better surface wetting resulting from increased surface energy, reduced and more uniform corrosion resistance, minimisation of external surface soiling and improved cleanability. The externally applied magnetic force for use with the enhanced electropolishing process may be selected from a group consisting of either permanent magnetic or electromagnetic devices. It has been shown that the enhanced electropolishing process results in better surface performance. In the present paper, for comparison purposes, results of surface roughness, hydrophilicity and corrosion behaviour are presented. Further studies, concerning the corrosion characteristics, the morphology and surface film chemistry, are in progress. [ABSTRACT FROM AUTHOR]