Effects of Sodium Fluoride on Structure and Corrosion Resistance of Plasma Electrolytic Oxidation Ceramic Coatings on Magnesium Alloys

The aim of this work is to investigate the effects of different power modes [constant current (CC), constant voltage (CV) and constant power (CP)] on the structure and corrosion resistance of the plasma electrolytic oxidation ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology and element distribution of the coatings were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings in the simulated body fluid was examined by electrochemical impedance spectroscopy and polarisation curve methods. The results showed that the coatings were of porous structure and mainly composed of MgO. The thickness, surface roughness, the size of the surface micropores and the amount of MgO were all increased with the cell voltage under the same power mode or increased in the sequence CV.CC.CP under the different power modes. The corrosion resistance of coatings was related to the structure characteristics, which were determined by different power modes. Among the different power modes, the corrosion resistance of the coatings is generally increased in the sequence CV.CP.CC, and under the same mode, the proper increase in the cell voltage is liable for improving the corrosion resistance of the coatings.

show abstract

“…According to our previous study, 15 the equivalent circuit of EIS spectra ,R s {Q 1 [R 1 (Q 2 R 2 )]}. was adopted.…”

Section: Corrosion Resistance Of Coatingsmentioning

confidence: 99%

“…Figure 5 is EIS (Nyquist plot) of the coatings prepared under different power modes. According to our previous study, 15 the equivalent circuit of EIS spectra ,R s {Q 1 [R 1 (Q 2 R 2 )]}. was adopted.…”

Section: Eis Measurement and Analysismentioning

confidence: 99%

Effect of PEO power modes on structure and corrosion resistance of ceramic coatings on AZ91D Mg alloy

Yao

Wang

Xia

et al. 2012

Surface Engineering

View full text Add to dashboard Cite

show abstract

“…To compare different "equivalent circuit" models, three kinds of "equivalent circuit" models were selected in this work. The first one is the simplest R s (QR) model, and R s is the solution resistance, Q and R are the constant phase elements (CPE), and the resistance of the whole coating; the second one is [24] and [25], Q 1 and R 1 are the CPE and the pore resistance of outer layer and Q 2 and R 2 are the CPE and the resistance of inner layer, in this model the two layer structure of the coatings are not divided completely; the last one is the R s (Q 1 R 1 ) (Q 2 R 2 ) model, which presents that the two layers are completely separated, and the equivalent circuit elements in the model have the similar meaning as the second one. All the corresponding fitting results are shown in Table II.…”

Section: Eis Analysis Of the Coatingsmentioning

confidence: 99%

Structure and Corrosion Resistance of PEO Ceramic Coatings on AZ91D Mg Alloy Under Three Kinds of Power Modes

Jiang

Xia

et al. 2012

Int J Applied Ceramic Tech

View full text Add to dashboard Cite

Power mode is one of the most important factors in the plasma electrolytic oxidation (PEO) technique, which greatly influences the structure and performances of the prepared ceramic coatings. The aim of this work was to investigate effects of three kinds of power modes (constant voltage (Mode 1), constant current (Mode 2), and constant power (Mode 3)) on the structure and corrosion resistance of the PEO ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology, and the element distribution of the coatings was studied using X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy, respectively. The electrochemical impedance spectrum was measured to evaluate the structure and the corrosion resistance. The polarizing curves were measured to evaluate the corrosion resistance. The results show that the coatings are of porous structure and mainly composed of MgO. The thickness and surface roughness of three kinds of coatings abide by the following sequences: Mode 1 > Mode 2 > Mode 3. By comparison, “equivalent circuit” mode Rs{Q1[R1(Q2R2)]} is the most proper to reflect the structure of such coatings, including the surface roughness, the outer layer pore structure, and the inner layer structure. The coatings prepared under Mode 1 are of maximum thickness and high density, and therefore have the best general corrosion resistance. And the coatings prepared under Mode 3 are of the smallest surface roughness and higher density, which leads to the best pitting corrosion resistance.

show abstract

“…It is noteworthy that uncoated Mg was studied only in Reference [28]. Other authors related the diameter of the high-frequency loop to the corrosion products or coatings and the diameter of the medium frequency loopto the charge transfer process [9,15,[19][20][21]39,42,52]. The second attribution has been successfully used in multiple studies on the protective behaviour of organic coatings on metal surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, monitoring electrochemical parameters as functions of time by this technique is a challenging task [10], while the obtained results cannot be accurately interpreted by a simple comparison of numerical values. Thus, the presence of one or two capacitive loops at high and medium frequencies and an inductive loop at low frequencies is common for the Nyquist plots of the coated and uncoated Mg alloys exposed to saline [11 36] and simulated physiological or buffer solutions [37 58]. However, some authors did not mention or include the inductive loop in their analysis even when they were clearly seen in their impedance diagrams [38,39,43].…”

Section: Introductionmentioning

confidence: 99%

Corrosion rates of reabsorbable Mg-based materials coated with phytic acid

Hernández-Alvarado

Lomeli

Miranda

et al. 2021

Corrosion Engineering, Science and Technology

View full text Add to dashboard Cite

The development of temporary protective coatings on magnesium implants is a priority in the biomedical field. In the present study, corrosion rates were determined by various techniques for powder metallurgy Mg and AZ31 magnesium alloy uncoated and coated with phytic acid (PA). Weight loss measurements, potentiodynamic polarisation, and electrochemical impedance spectroscopy were performed to monitor the corrosion evolution in a phosphate-buffered saline solution at 37°C. The corrosion rates of all samples determined from weight losses were higher than those obtained by electrochemical techniques. According to electrochemical data, the initial corrosion current density of the coated samples decreased by three orders of magnitude as compared with that of the bare substrates. However, the protective effect weakened with the testing time due to the presence of microcracks in the PA conversion coating, which indicated the potential applicability of the coated AZ31 alloy as a biodegradable and resorbable temporary implant material for bone repair.

show abstract

Effects of Sodium Fluoride on Structure and Corrosion Resistance of Plasma Electrolytic Oxidation Ceramic Coatings on Magnesium Alloys

Cited by 6 publications

References 14 publications

Effect of PEO power modes on structure and corrosion resistance of ceramic coatings on AZ91D Mg alloy

Effect of PEO power modes on structure and corrosion resistance of ceramic coatings on AZ91D Mg alloy

Structure and Corrosion Resistance of PEO Ceramic Coatings on AZ91D Mg Alloy Under Three Kinds of Power Modes

Corrosion rates of reabsorbable Mg-based materials coated with phytic acid

Contact Info

Product

Resources

About