Pulsed nanocrystalline plasma electrolytic boriding as a novel method for corrosion protection of CP-Ti (Part 1: Different frequency and duty cycle)

REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations demand for an expedient discovery of a Cr(VI)-free alternative corrosion protection for light alloys even though the green alternatives might never be as cheap as current harmful technologies. In the present work, flash- plasma electrolytic oxidation coatings (FPEO) with the process duration < 90 s are developed on AZ31B alloy in varied mixtures of silicate-, phosphate-, aluminate-, and fluoride-based alkaline electrolytes implementing current density and voltage limits. The overall evaluation of the coatings’ anticorrosion performance (electrochemical impedance spectroscopy (EIS), neutral salt spray test (NSST), paintability) shows that from nine optimized FPEO recipes, two (based on phosphate, fluoride, and aluminate or silicate mixtures) are found to be an adequate substitute for commercially used Cr(VI)-based conversion coating (CCC). The FPEO coatings with the best corrosion resistance consume a very low amount of energy (~1 kW h m−2 µm−1). It is also found that the lower the energy consumption of the FPEO process, the better the corrosion resistance of the resultant coating. The superb corrosion protection and a solid environmentally friendly outlook of PEO-based corrosion protection technology may facilitate the economic justification for industrial end-users of the current-consuming process as a replacement of the electroless CCC process.

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Effect of Power Duty Cycle on Plasma Electrolytic Oxidation of A356-Nb2O5 Metal Matrix Composites

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05597-4 ◽

2021 ◽

Vol 30 (4) ◽

pp. 2586-2604

Author(s):

Reyhan Bahador ◽

Navid Hosseinabadi ◽

Amirhossein Yaghtin

Keyword(s):

Metal Matrix Composites ◽

Duty Cycle ◽

Metal Matrix ◽

Plasma Electrolytic Oxidation ◽

Matrix Composites ◽

Electrolytic Oxidation ◽

Plasma Electrolytic

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Comparison of Biocompatible Coatings Produced by Plasma Electrolytic Oxidation on cp-Ti and Ti-Zr-Nb Superelastic Alloy

Coatings ◽

10.3390/coatings11040401 ◽

2021 ◽

Vol 11 (4) ◽

pp. 401

Author(s):

Ruzil Farrakhov ◽

Olga Melnichuk ◽

Evgeny Parfenov ◽

Veta Mukaeva ◽

Arseniy Raab ◽

...

Keyword(s):

Plasma Electrolytic Oxidation ◽

Electrochemical Impedance ◽

Pure Titanium ◽

Commercially Pure Titanium ◽

X Ray ◽

Kinetic Coefficients ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Cp Ti ◽

Peo Coatings

The paper compares the coatings produced by plasma electrolytic oxidation (PEO) on commercially pure titanium and a novel superelastic alloy Ti-18Zr-15Nb (at. %) for implant applications. The PEO coatings were produced on both alloys in the identical pulsed bipolar regime. The properties of the coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The PEO process kinetics was modeled based on the Avrami theorem and Cottrell equation using a relaxation method. The resultant coatings contain TiO2, for both alloys, and NbO2, Nb2O5, ZrO2 for Ti-18Zr-15Nb alloy. The coating on the Ti-18Zr-15Nb alloy has a higher thickness, porosity, and roughness compared to that on cp-Ti. The values of the kinetic coefficients of the PEO process—higher diffusion coefficient and lower time constant for the processing of Ti-18Zr-15Nb—explain this effect. According to the electrochemical studies, PEO coatings on Ti-18Zr-15Nb alloy provide better corrosion protection. Higher corrosion resistance, porosity, and roughness contribute to better biocompatibility of the PEO coating on Ti-18Zr-15Nb alloy compared to cp-Ti.

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Effect of Duty Cycle on Properties of Al2O3 Ceramic Coatings Fabricated on TiAl Alloy via Cathodic Plasma Electrolytic Deposition

Materials ◽

10.3390/ma11101962 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1962 ◽

Cited By ~ 1

Author(s):

Shaoqing Wang ◽

Faqin Xie ◽

Xiangqing Wu ◽

Jixiang An

Keyword(s):

Electron Microscopy ◽

Wear Resistance ◽

Heat Resistance ◽

Duty Cycle ◽

Tial Alloy ◽

Ceramic Coatings ◽

Electrolytic Deposition ◽

Al2o3 Ceramic ◽

Cathodic Plasma ◽

Plasma Electrolytic

In order to study the effect of duty cycle during the cathodic plasma electrolytic deposition (CPED) process, Al2O3 ceramic coatings were fabricated via the CPED technique on prepared TiAl alloy in an Al(NO3)3 electrolyte with different duty cycles. Microstructure, morphology, and chemical compositions of coatings were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The mechanical properties, such as thickness, hardness, and binding strength, were also characterized, and heat-resistance and wear-resistance tested. The results indicated that duty cycle mainly affected the relative crystallinity of CPED coatings. As the duty cycle increased, the crystallinity of CPED coatings increased, the content of Al(OH)3 and γ-Al2O3 decreased, and the content of α-Al2O3 increased. The thickness and bonding strength both increased firstly and then decreased, while hardness increased as duty cycle increased. Heat-resistance and wear-resistance of TiAl alloy with CPED coating was highly improved compared to that of TiAl alloy substrate without CPED coating.

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Advanced Corrosion Protection of Additive Manufactured Light Metals by Creating Ceramic SurfaceThrough CERANOD® Plasma Electrolytical Oxidation Process

Frontiers in Chemical Engineering ◽

10.3389/fceng.2021.734644 ◽

2021 ◽

Vol 3 ◽

Author(s):

Patcharawee Jantimapornkij ◽

Jörg Zerrer ◽

Anna Buling

Keyword(s):

Corrosion Protection ◽

Electrochemical Impedance ◽

Wear Behavior ◽

Light Metal ◽

Localized Corrosion ◽

Full Potential ◽

Oxide Ceramic ◽

Light Metals ◽

Metal Printing ◽

Plasma Electrolytic

Lightweight structures produced by additive manufacturing (AM) technology such as the selective laser melting (SLM) process enable the fabrication of 3D structures with a high degree of freedom. A printed component can be tailored to have specific properties and render possible applications for industries such as the aerospace and automotive industries. Here, AlSi10Mg is one of the alloys that is currently used for SLM processes. Although the research with the aim improving the strength of AM aluminum alloy components is rapidly progressing, corrosion protection is scarcely addressed in this field. Plasma electrolytic oxidation (PEO) is an advanced electrolytical process for surface treatment of light metals such as aluminum, magnesium, and titanium. This process produces an oxide ceramic-like layer, which is extremely hard but also ductile, and significantly improves the corrosion and wear behavior. The aim of this study is to understand the corrosion behavior of 3D-printed AlSi10Mg alloy and to improve its corrosion resistance. For this reason, the properties of CERANOD®—PEO coating on an AlSi10Mg alloy produced by SLM were investigated on different AM surfaces, i.e., as-built, polished and stress relieved specimens. The corrosion performance of these surfaces was analyzed using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and long-term immersion tests. Moreover, the microstructure and morphology of the resulting coatings were characterized by SEM/EDS, taking into account the corrosive attacks. The results exhibited a high amount of localized corrosion in the case of the uncoated specimens, while the PEO process conducted on the aluminum AM surfaces led to enclosed homogeneous coatings by protecting the material’s pores, which are typically observed in AM process. Thereby, high corrosion protection could be achieved using PEO surfaces, suggesting that this technology is a promising candidate for unleashing the full potential of 3D light metal printing.

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