Microstructure and corrosion resistance of the PEO coating on extruded Al6Cu alloy

Zhu, Li; Qiu, Ji; Chen, Jinhui; Zhang, Wei; Chen, Zhixiong; Zhang, Tao; Wang, Fuhui

doi:10.1016/j.surfcoat.2019.04.027

Cited by 24 publications

(11 citation statements)

References 33 publications

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“…It directly measures the stability (corrosion resistance) of the PEO coating. [ 46,74 ] The slope of 1/ C 2 versus E plots is not similar in all frequencies. [ 95 ] High frequencies are preferred because the effect of the double‐layer capacitance is negligible at high frequencies.…”

Section: Understanding Eis Of Peo Coatingsmentioning

confidence: 99%

“…The inclusion of Q dl /R ct can be either with the inner layer (Q in /R in ) and the surviving however damaged outer-layer (Q out /R out ) components (Figure 5B) or with a Q coat /R coat for severely broken coating with many pores (Figure 5C). [44,73,74] The capacitance values (derived from Q ) can help differentiate the capacitive loop of Q dl /R ct from that of coating layers because C dl values are generally in the μF range. However, the capacitances of PEO coating layers usually have lower values (10 À7 -10 À9 F).…”

Section: Correlating Peo Coating To Equivalent Circuit Modelsmentioning

confidence: 99%

“…The equivalent circuits used for the EIS data fitting of PEO coatings after the commencement of noticeable corrosion generally include two-or three-time constants. [73,74] The barrier nature of the coating drops for corroding PEO coatings. Therefore, a new capacitive loop corresponding to the electrolyte/metal interface (Q dl /R ct ) representing the corrosion of the substrate metal appears at the lowest-frequency regions.…”

Section: Correlating Peo Coating To Equivalent Circuit Modelsmentioning

confidence: 99%

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A Review on the Application‐Focused Assessment of Plasma Electrolytic Oxidation (PEO) Coatings Using Electrochemical Impedance Spectroscopy

Dilimon

Shibli

2023

Adv Eng Mater

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Background of this ReviewPlasma electrolytic oxidation (PEO), micro-arc oxidation, and micro-plasma oxidation are alternative names for the same surfacecoating technology for producing multiple layers of ceramic oxides on the surface of light valve metals such as Al, Mg, Ti, Zr, Ta, Nb, Hf, and their alloys. Oxidation potentials higher than the dielectric breakdown voltage of the first formed passive film are applied through a suitable electrolyte. This high applied potential (400-600 V or higher) generates plasma discharges on the workpiece metal surface, and this plasma creates ideal conditions of high temperatures and pressures for the formation of hardened, crystalline, well-adherent, and corrosion-resistant oxide layers.The PEO process has several benefits over the conventional electrolytic oxidation process. Surface coatings formed through the PEO process have two to four times higher hardness. Their unique porous outer layer permits material scientists and engineers to customize the coating performance by incorporating different reagents, particles, and functionalities. The coating thickness can be varied from a few micrometers to more than 100 μm depending on the final target application of PEO coatings. The chemical passivity and inertness of PEO coatings enable their application in harsh environments. Reduced stiffness and crack-free edges of PEO coatings give better adhesion, making them suitable for applications under mechanical strain or thermal cycling. Also, PEO coatings technology is used for making biodegradable orthopedic implants. [1,2] PEO process with nontoxic electrolytes is an environmentally friendly technology. Qin et al. reported the preparation method of degradation resistant and in vitro cytocompatible PEO coatings on biomedical Mg alloys in green, nontoxic, and recyclable electrolytes. [3] Recent review papers describe the present status of PEO coating technology on different metals and alloys. [4][5][6][7][8][9] The last 20 years show a remarkable increase in publication numbers related to PEO coatings (Figure 1). Among them, the number of publications describing electrochemical impedance spectroscopy (EIS) for PEO coating analysis is also considerably increasing (Figure 1).The PEO coatings contain various oxides of base metals, additives, and electrolyte-borne species from the electrolyte. [10][11][12] Recent review papers describe in detail the effect of particle addition into the PEO coatings on the microstructure, composition, and corrosion behavior of coatings studied by different microscopic, spectroscopic, and electrochemical techniques. [13][14][15][16][17][18][19][20] Also, several recent research papers discuss the EIS assessment of particle-incorporated PEO coatings. [21][22][23] To a large extent, the inclusion of additives occurs in the PEO coating's outer layer, while the inner layer is mainly metal oxide of the substrate metal. [8] The size of incorporated particles in PEO coatings is in either nano or micro ranges. Recent review papers discuss the PEO coating's perfor...

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Section: Understanding Eis Of Peo Coatingsmentioning

confidence: 99%

Section: Correlating Peo Coating To Equivalent Circuit Modelsmentioning

confidence: 99%

Section: Correlating Peo Coating To Equivalent Circuit Modelsmentioning

confidence: 99%

See 1 more Smart Citation

A Review on the Application‐Focused Assessment of Plasma Electrolytic Oxidation (PEO) Coatings Using Electrochemical Impedance Spectroscopy

Dilimon

Shibli

2023

Adv Eng Mater

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“…In addition, since the heat conductivity of static air is as low as 0.026 W/(m•k), an increase in coating porosity will contribute to an improvement in the thermal insulation performance of coatings. In addition, the spark breakdown characteristic of the PEO technology can give rise to a large number of pores in coatings [13][14][15]. Therefore, the PEO technology has an inherent advantage when producing coatings with low heat capacity and low heat conductivity.…”

Section: Introductionmentioning

confidence: 99%

Influence of Applied Frequency on Thermal Physical Properties of Coatings Prepared on Al and AlSi Alloys by Plasma Electrolytic Oxidation

et al. 2021

Coatings

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In this study, plasma electrolytic oxidation (PEO) was performed on Al and AlSi substrates using a pulsed direct current (DC) power source. The coating process was carried out in a Na2SiO3 electrolyte with the systematic change of pulse frequency (50–1400 Hz). The surface characteristics of the coatings were examined using scanning electron microscopy (SEM). The phase structure was characterized using X-ray diffraction (XRD). A differential scanning calorimeter (DSC) and a laser flash apparatus (LFA) were employed to test heat capacity and heat conductivity, respectively. Results showed that as the discharge frequency increased, the thermal physical properties of Al-PEO and AlSi-PEO coatings changed in different ways. At a high frequency, Al-PEO coatings had low porosity and were closed-pore structured whereas AlSi-PEO coatings had high porosity and large-size open-pore structures could be observed on their surfaces due to concentrated discharges. Based on these findings, it was found that the thermal productivity of coatings is closely correlated with the open-/closed-pore structure instead of porosity. PEO coatings with low heat capacity or low heat conductivity could be obtained with a controlled frequency.

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“…The inhibition effect was explained on to the difference in the diffusion rate of the corrosion product across the fine and coarse grained microstructure. Corrosion protection of PEO coating on extruded Al6Cu alloy in 3.5% wt NaCl was evaluated 23 . The corrosion protection of Al6Cu alloy was enhanced in the presence of PEO coating compared to as-cast alloy due to the change in its microstructure.…”

Section: Introductionmentioning

confidence: 99%

Role of S2− ions on the microstructure change and the pitting behaviour of aluminum in saline solution

El-Deeb

2019

Sci Rep

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The electrochemical behaviour and the passive film microstructure of aluminum during its exposure to 3.5 wt% NaCl solution in the absence and presence of S 2− ions are investigated using potentiodynamic polarization curves, electrochemical impedance spectroscopy measurements, XRD, XRF, SEM and AFM. Electrochemical measurements show that the presence of S 2− ions enhances the uniform corrosion of aluminum in NaCl solution, but delay its susceptibility to the pitting corrosion. In addition, EIS analysis illustrate that the formation of more compact and protective passive layer in the presence of S 2− ions compared to its rough surface in the absence of S 2− ions as evidenced by the lower value of constant phase element ( CPE ) and higher value of phase shift ( N ). Cracks, non- homogenous and open large pits with high degree of roughness are clearly observed on the aluminum surface in the absence of S 2− ions, compared to oriented grooves, elongated ridges with the accumulation of the corrosion products inside the pits in the presence of S 2− ions. The inhibitory effect of S 2− ions for the pitting corrosion of aluminum is interpreted on the basis of the change in its microstructure of the passive film in the absence and presence of S 2− ions.

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Microstructure and corrosion resistance of the PEO coating on extruded Al6Cu alloy

Cited by 24 publications

References 33 publications

A Review on the Application‐Focused Assessment of Plasma Electrolytic Oxidation (PEO) Coatings Using Electrochemical Impedance Spectroscopy

A Review on the Application‐Focused Assessment of Plasma Electrolytic Oxidation (PEO) Coatings Using Electrochemical Impedance Spectroscopy

Influence of Applied Frequency on Thermal Physical Properties of Coatings Prepared on Al and AlSi Alloys by Plasma Electrolytic Oxidation

Role of S2− ions on the microstructure change and the pitting behaviour of aluminum in saline solution

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