Effect of pH value and preparation temperature on the formation of magnesium phosphate conversion coatings on AZ31 magnesium alloy

Zai, Wei; Su, Yingchao; Man, Hau Chung; Lian, Jianshe; Li, Guangyu

doi:10.1016/j.apsusc.2019.05.309

Cited by 81 publications

(18 citation statements)

References 58 publications

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“…35-0780). Previous studies have also shown that the MgHPO 4 ·3H 2 O can be formed in a phosphate buffer solution with a constant pH of 6.8 [ 43 ]. However, due to the relatively thin and fragile corrosion layer, the magnesium hydroxide cannot be detected and the result of magnesium hydrogen phosphate in SIF without pancreatin is not obvious.…”

Section: Resultsmentioning

confidence: 99%

“…10(c2) ). The diffusion zone between the conversion solution and Mg-P film transfers Mg ions and hydrogen gas to the solution and conversely transfers HPO 4 2− and H + ions from the solution to the Mg-P film [ 43 ]. It is recognized that the hydrogen phosphate is beneficial to decrease the corrosion rate and uniform corrosion of magnesium alloys [ 26 , 28 ].…”

Section: Discussionmentioning

confidence: 99%

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The effect of enzymes on the in vitro degradation behavior of Mg alloy wires in simulated gastric fluid and intestinal fluid

Zhang

Cao

Wang

et al. 2022

Bioactive Materials

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With an upsurge of biodegradable metal implants, the research and application of Mg alloys in the gastrointestinal environment of the digestive tract have been of great interest. Digestive enzymes, mainly pepsin in the stomach and pancreatin in the small intestine, are widespread in the gastrointestinal tract, but their effect on the degradation of Mg alloys has not been well understood. In this study, we investigated the impacts of pepsin and pancreatin on the degradation of Mg-2Zn alloy wires. The results showed that the pepsin and pancreatin had completely different even the opposite effects on the degradation of Mg, although they both affected the degradation product layer. The degradation rate of Mg wire declined with the addition of pepsin in simulated gastric fluid (SGF) but rose with the addition of pancreatin in simulated intestinal fluid (SIF). The opposite trends in degradation rate also resulted in completely different degradation morphologies in wires surface, where the pitting corrosion in SGF was inhibited because of the physical barrier effect of pepsin adsorption. In contrast, the adsorption of pancreatin affected the integrity of magnesium hydrogen phosphate film, causing a relatively uneven degraded surface. These results may help us to understand the role of different digestive enzymes in the degradation of magnesium and facilitate the development and clinical application of magnesium alloy implanted devices for the digestive tract.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The effect of enzymes on the in vitro degradation behavior of Mg alloy wires in simulated gastric fluid and intestinal fluid

Zhang

Cao

Wang

et al. 2022

Bioactive Materials

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“…A layer of dense coating is revealed in Figures 2 and 3 , and here, its formation mechanism is simply discussed as follows. Firstly, H 2 PO 4 − ionizes in aqueous solutions to release HPO 4 2- and H + [ 26 , 27 ]. Next, HPO 4 2- preferentially bonds with Ca 2+ to form insoluble CaHPO 4 ·2H 2 O in this acidic phosphate solution, whose related chemical reaction is shown below: Ca 2+ + HPO 4 2- + 2 H 2 O → CaHPO 4 ∙2H 2 O [ 28 , 29 ].…”

Section: Resultsmentioning

confidence: 99%

Improving Corrosion Resistance of Magnesium Alloy in Cl- Containing Simulated Concrete Pore Solution by Ultrasound-Assisted Chemical Deposition

Wang

2021

Scanning

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Coatings are playing an important role in corrosion mitigation of magnesium alloys, and in this study, a facile and eco-friendly chemical deposition process is proposed to improve the corrosion resistance of magnesium-neodymium alloys. The mixture of 1.5 mol/L KH2PO4 solution and 1.2 mol/L CaCl2 solution is used for reaction solution, and ultrasound is introduced into the process for assisting the chemical deposition. After 40 minutes of the surface treatment, the surface and cross-sectional morphologies are observed by scanning electron microscope (SEM), which reveals that a layer of dense coating is formed on Mg alloy. Energy-dispersive X-ray spectroscopy (EDS) and X-ray Diffraction (XRD) are further combined to analyze the coating, and it is thereby confirmed that this coating mainly consists of CaHPO4·2H2O. Electrochemical tests and soaking experiments are conducted to evaluate the corrosion resistance of the treated samples in simulated concrete pore solutions. Both the untreated and treated samples have a good corrosion resistance in the Cl- free simulated concrete pore solution, but their corrosion behavior is influenced by the introduction of Cl- in this study. Fortunately, the coating can protect the substrate effectively in the Cl- containing simulated concrete pore solution. In summary, it provides a possible way for magnesium alloys to improve their corrosion resistance when they are used in building engineering.

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“…In general, a conversion coating works by stimulating the interfacial reactions with the subsequent precipitation/coating formation. The process is triggered by a decrease of the pH and an increase of the Mg 2+ concentration at the metal/solution interface [ 62 ]. Mg's low standard electrode potential allows protons (H + ) and water to be reduced simultaneously upon dissolution.…”

Section: Coatings and Their Current Statusmentioning

confidence: 99%

Progress in bioactive surface coatings on biodegradable Mg alloys: A critical review towards clinical translation

Singh

Batra

Kumar

et al. 2023

Bioactive Materials

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Effect of pH value and preparation temperature on the formation of magnesium phosphate conversion coatings on AZ31 magnesium alloy

Cited by 81 publications

References 58 publications

The effect of enzymes on the in vitro degradation behavior of Mg alloy wires in simulated gastric fluid and intestinal fluid

The effect of enzymes on the in vitro degradation behavior of Mg alloy wires in simulated gastric fluid and intestinal fluid

Improving Corrosion Resistance of Magnesium Alloy in Cl- Containing Simulated Concrete Pore Solution by Ultrasound-Assisted Chemical Deposition

Progress in bioactive surface coatings on biodegradable Mg alloys: A critical review towards clinical translation

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