An insight into the evolution of corrosion resistant coatings on titanium during bipolar plasma electrolytic oxidation in sulfuric acid

Casanova, Luca; Padula, Marcello La; Pedeferri, MariaPia; Diamanti, Maria Vittoria; Ormellese, Marco

doi:10.1016/j.electacta.2021.138190

Cited by 18 publications

(22 citation statements)

References 54 publications

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“…The pulsed anodization signal was designed according to the fully programmable California Instruments Asterion 751 series AC/DC power source using a duty cycle of 60A%-40C%-7CP% repeated at 1000 Hz, where "A" and "C" stand for anodic and cathodic polarization, while CP indicates the % of cathodic polarization applied with respect to the anodic one. This waveform was selected as it was demonstrated to be particularly useful for corrosion resistance enhancement in our previous paper [7]. Conversion treatments were performed under a potential-controlled regime considering a forming voltage of 90 V reached through a constant ramp, leading to a total treatment time of 320 s. Current and voltage curves, recorded during PEO treatments, were acquired using a Tektronix TBS-1072B-EDU oscilloscope(Tektronix, Beaverton, Oregon).…”

Section: Methodsmentioning

confidence: 99%

“…In particular, when using acetic acid, a porous surface, common [35] to PEO treatments performed in low pH environments [3,7], developed with pore diameters of ~0.98 ± 0.3 µm. The pores' number was substantially reduced when using lactic (Figures 6 and 7) and citric (Figure 6m, even if their size was markedly increased (~4.64 ± 2.1 µm for PEO-LA and ~18.5 ± 3.4 µm for PEO-CI).…”

Section: Oxide Morphology and Compositionmentioning

confidence: 99%

“…One of the most promising electrochemical techniques to achieve this purpose is plasma electrolytic oxidation (PEO), which allows one to increase the oxide thickness well beyond one micron [3,4]. PEO consists in a high-voltage anodic oxidation applied on valve metals such as Al, Mg and Ti, generally in alkaline solutions [5,6], even if, quite recently, PEO on Ti using sulfuric acid was verified to be highly effective for corrosion resistance enhancement [7]. This allowed oxide with thicknesses in the range ~2 ÷ 8 µm to be obtained, showing very good adherence and stability when immersed in strongly acidic solutions, such as 10% v/v H 2 SO 4 at 60 • C, and, in some cases, making it possible to overcome performances of Ti grade 7.…”

Section: Introductionmentioning

confidence: 99%

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Addition of Organic Acids during PEO of Titanium in Alkaline Solution

et al. 2022

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This research study describes recent advances in understanding the effects of the addition of organic acids, such as acetic, lactic, citric and phytic acids, on the process of plasma electrolytic oxidation (PEO) on Ti using an alkaline bath. As the plasma developed over the workpiece is central to determine the particular morphological and structural features of the growing oxide, the focus is then on the inter-relationships between the electrolyte and the resultant plasma regime established. In situ optical emission spectroscopy (OES) allowed us to verify a marked plasma suppression when adding low-molecular-weight anions such as acetates, resulting in short-lived and well-distributed discharges. Conversely, when more bulky anions, such as lactates, citrates and phytates, were considered, a less efficient shielding of the electrode caused the build-up of long-lasting and destructive sparks responsible for the formation of thicker coatings, even >30 µm, at the expense of a higher roughness and loss of compactness. Corrosion resistance was tested electrochemically, according to electrochemical impedance spectroscopy (EIS), and weight losses evidenced the coatings produced in the solution containing acetates to be more suitable for service in H2SO4.

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Section: Methodsmentioning

confidence: 99%

Section: Oxide Morphology and Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Addition of Organic Acids during PEO of Titanium in Alkaline Solution

et al. 2022

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“…Therefore, an in-depth evaluation of the PEO process and resultant coatings during the treatment are crucial for the development of a high-quality biocompatible coating. Nowadays, investigations into the early stages of the Al [ 25 ], Mg [ 26 , 27 ], and Ti [ 28 , 29 ] PEO show new insights into the process mechanism. Due to the different electric regimes, not all results are comparable.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

et al. 2021

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The problem of the optimization of properties for biocompatible coatings as functional materials requires in-depth understanding of the coating formation processes; this allows for precise manufacturing of new generation implantable devices. Plasma electrolytic oxidation (PEO) opens the possibility for the design of biomimetic surfaces for better biocompatibility of titanium materials. The pulsed bipolar PEO process of cp-Ti under voltage control was investigated using joint analysis of the surface characterization and by in situ methods of impedance spectroscopy and optical emission spectroscopy. Scanning electron microscopy, X-ray diffractometry, coating thickness, and roughness measurements were used to characterize the surface morphology evolution during the treatment for 5 min. In situ impedance spectroscopy facilitated the evaluation of the PEO process frequency response and proposed the underlying equivalent circuit where parameters were correlated with the coating layer properties. In situ optical emission spectroscopy helped to analyze the spectral line evolutions for the substrate material and electrolyte species and to justify a method to estimate the coating thickness via the relation of the spectral line intensities. As a result, the optimal treatment time was established as 2 min; this provides a 9–11 µm thick PEO coating with Ra 1 µm, 3–5% porosity, and containing 75% of anatase. The methods for in-situ spectral diagnostics of the coating thickness and roughness were justified so that the treatment time can be corrected online when the coating achieves the required properties.

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“…To improve the performance of light metals (Mg, Al, Ti, etc.) and their alloys, wet surface treatments, including chemical conversion, anodizing, and plasma electrolysis (PE) have been employed to deposit a protective layer on the metallic surface [1][2][3][4][5]. Among these strategies, PE (also denoted as micro-arc oxidation) is able to reform the surface of Mg, Al, Ti under high electrical polarization by utilizing myriads of plasma discharges accompanying the formation of an inorganic layer (IL) [1,4].…”

Section: Introductionmentioning

confidence: 99%

Hybrid Organic-Inorganic Materials on Metallic Surfaces: Fabrication and Electrochemical Performance

Nashrah

Putri

Alharissa

et al. 2021

Metals

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In recent years, hybrid organic-inorganic (HOI) materials have attracted massive attention as they combine the unique properties of organic and inorganic compounds. In this review, we focus on the formation of HOI materials and their electrochemical performance that can be controlled by microstructural design depending upon their chemical composition. This overview outlines the recent strategies of preparing HOI materials on metallic surface via wet-electrochemical systems, such as plasma electrolysis (PE) and dip chemical coating (DCC). The corresponding electrochemical behavior for short and long term exposures is also summarized.

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An insight into the evolution of corrosion resistant coatings on titanium during bipolar plasma electrolytic oxidation in sulfuric acid

Cited by 18 publications

References 54 publications

Addition of Organic Acids during PEO of Titanium in Alkaline Solution

Addition of Organic Acids during PEO of Titanium in Alkaline Solution

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

Hybrid Organic-Inorganic Materials on Metallic Surfaces: Fabrication and Electrochemical Performance

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