Comparison of plasma electrolytic oxidation coatings on Al alloy created in aqueous solution and molten salt electrolytes

Sobolev, Alexander; Kossenko, Alexey; Zinigrad, Michael; Borodianskiy, Konstantin

doi:10.1016/j.surfcoat.2018.03.091

Cited by 30 publications

(17 citation statements)

References 30 publications

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“…Usually, PEO treatment is conducted in an aqueous electrolyte made of silicates, phosphates, aluminates, fluorides, and other [7][8][9][10][11][12]. Recently, we have showed a possible implementation of the electrolyte of the molten salt in the PEO process [13][14][15]. Results of these works evaluated the formation of a denser coating free of any contaminants in comparison with a traditional method, which is usually obtained in an aqueous electrolyte.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

2020

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The fabrication of a ceramic coating on the metallic substrate is usually applied to achieve the improved performance of the material. Plasma electrolytic oxidation (PEO) is one of the most promising methods to reach this performance, mostly wear and corrosion resistance. Traditional PEO is carried out in an aqueous electrolyte. However, the current work showed the fabrication and characterization of a ceramic coating using PEO in molten salt which was used to avoid disadvantages in system heating-up and the formation of undesired elements in the coating. Aluminum 7075 alloy was subjected to the surface treatment using PEO in molten nitrate salt. Various current frequencies were applied in the process. Coating investigations revealed its surface porous structure and the presence of two oxide layers, α-Al2O3 and γ-Al2O3. Microhardness measurements and chemical and phase examinations confirmed these results. Potentiodynamic polarization tests and electrochemical impedance spectroscopy revealed the greater corrosion resistance for the coated alloy. Moreover, the corrosion resistance was increased with the current frequency of the PEO process.

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Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

2020

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“…In this work, it has been found that the formed coating was free of any contaminants originating from the electrolytes and had no cracks or pores, which are usually present in coatings formed by PEO treatment in an aqueous solution electrolyte. Other interesting results can be also found in [106] where the coating obtained in PEO treatment in molten salt consists of hard α-Al 2 O 3 and γ-Al 2 O 3 phases with a better corrosion resistance three times higher as compared to that treated in aqueous electrolyte solution.…”

Section: Corrosion Resistance Of Coatings Obtained By Different Surfamentioning

confidence: 69%

Corrosion of Cast Aluminum Alloys: A Review

Labari

Biezma

Rivero

2020

Metals

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Research on corrosion resistance of cast aluminum alloys is reviewed in this article. The effect of the main microstructural features of cast aluminum alloys such as secondary dendrite arm spacing (SDAS), eutectic silicon morphology, grain size, macrosegregation, microsegregation, and intermetallic compounds is discussed. Moreover, the corrosion resistance of cast aluminum alloys obtained by modern manufacturing processes such as semi-solid and additive manufacturing are analyzed. Finally, the protective effects provided by different coatings on the aluminum cast alloys—such as anodized, plasma electrolytic oxidation (PEO), and laser—is reviewed. Some conclusions and future guidelines for future works are proposed.

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“…The oxide layer, depending on composition, structure, and morphology, may possess both ionic and/or electronic conductivity with a wide range of activation energies. The electrolyte solution is, normally, a pure ionic conductor (although sometimes molten salts can be used as well) [55]. In such a circuit composed of materials with various types of conductivity, the transfer of charges and masses includes overcoming potential barriers at interphase contacts, as well as migration and diffusion within bulk phases.…”

Section: Load Analysismentioning

confidence: 99%

Smart Arbitrary Waveform Generator with Digital Feedback Control for High-Voltage Electrochemistry

Rogov¹

2019

Instruments

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This paper describes a design approach to a control system of power supply for high-voltage electrochemical processes such as plasma electrolytic oxidation (PEO) or high-voltage anodising (HVA), which require alternating polarisation pulses up to 750 V and a typical current density of 50–500 mA/cm2. Complex characteristics of the electrochemical system response on applied polarisations (positive or negative) cause necessity of precise control of polarising pulse shapes for better process operation and its understanding. A device performs cycle-by-cycle pulse-width modulation (PWM) control, including feedback based on digital analysis of the instantaneous current and/or voltage output, and the desired pulse waveform stored in memory for each output polarity. The output stage has four states corresponding to positive or negative pulses, as well as open- or short-circuit conditions, with respect to an electrochemical cell. A fully programmable controller allows one to generate arbitrary waveforms, as well as their sequences, by means of “regime designer” software. Moreover, a smart feedback system can provide adaptation of the next pulse parameter from analysis of the process prehistory. For instance, this approach allows one to separate main electrochemical process (coating formation) and diagnosis of the phenomenon through introduction of high-voltage triangular voltage sweep pulse within a pause of the main process, which is normally carried out under a current control.

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Comparison of plasma electrolytic oxidation coatings on Al alloy created in aqueous solution and molten salt electrolytes

Cited by 30 publications

References 30 publications

Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

Corrosion of Cast Aluminum Alloys: A Review

Smart Arbitrary Waveform Generator with Digital Feedback Control for High-Voltage Electrochemistry

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