Electrochemical studies on ammonium magnesium carbonate tetrahydrate/calcium carbonate composite coating on AZ91D magnesium alloy

Simultaneously Regulating Electrochemical Corrosion Behavior and Wettability of Magnesium–Neodymium Alloy by Self-Layered Chemical Conversion Coating

“…The equivalent circuit models for fitting are shown in Figure 11d. Roughly speaking, the larger the |Z| value at the lowest investigated frequency, the stronger the corrosion resistance [26,34]. It can be seen from Figure 11a that when the frequency is close to 0.1 Hz, the |Z| value of the coated sample is much larger than that of the uncoated sample.…”

“…Figure 11 a exhibits the Bode plots by impedance versus frequency and Figure 11 b shows the Bode plots by phase angle versus frequency, Figure 11 c gives the Nyquist plots. The equivalent circuit models for fitting are shown in Figure 11 d. Roughly speaking, the larger the |Z| value at the lowest investigated frequency, the stronger the corrosion resistance [ 26 , 34 ]. It can be seen from Figure 11 a that when the frequency is close to 0.1 Hz, the |Z| value of the coated sample is much larger than that of the uncoated sample.…”

“…Among them, chromate coating is commonly used as an anti-corrosion coating for magnesium alloy because of its excellent corrosion resistance, self-healing performance, and relatively mature process. However, Cr 6+ is highly toxic and poses a significant threat to humans and the environment [ 17 , 26 ]. Therefore, its industrial applications have been restricted.…”

Antibacterial Activity and Cell Viability of Biomimetic Magnesian Calcite Coatings on Biodegradable Mg

“…Oxide-carbonate coatings have also demonstrated self-healing performance on the surface of AZ41 Mg alloy via ultrasound-assisted chemical conversion [ 8 ]. Several studies [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] have reported the development of single-layer carbonate coatings to control the corrosion of Mg and alloys: a protective MgCO 3 layer was obtained by electron beam irradiation inside an environmental TEM [ 9 ], a continuous protective film of nesquehonite was grown directly on Mg in humid CO 2 at 40 °C and 65 atm in a pressure autoclave [ 10 ], and protective layers of Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O [ 11 ] and CaCO 3 [ 12 ] were obtained by hydrothermal synthesis. Recently, Ca(Mg)CO 3 coatings providing a much improved corrosion resistance in isotonic physiological fluids containing chloride ions were grown on pure Mg [ 13 ] and on AZ91 Mg alloy [ 14 ] via simple green conversion methods in aqueous solution; on Mg2Zn0.2Ca alloy via hydrothermal method [ 12 , 15 ]; and on Mg-Nd alloy by ultrasound-assisted chemical conversion [ 17 ].…”

“…Several studies [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] have reported the development of single-layer carbonate coatings to control the corrosion of Mg and alloys: a protective MgCO 3 layer was obtained by electron beam irradiation inside an environmental TEM [ 9 ], a continuous protective film of nesquehonite was grown directly on Mg in humid CO 2 at 40 °C and 65 atm in a pressure autoclave [ 10 ], and protective layers of Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O [ 11 ] and CaCO 3 [ 12 ] were obtained by hydrothermal synthesis. Recently, Ca(Mg)CO 3 coatings providing a much improved corrosion resistance in isotonic physiological fluids containing chloride ions were grown on pure Mg [ 13 ] and on AZ91 Mg alloy [ 14 ] via simple green conversion methods in aqueous solution; on Mg2Zn0.2Ca alloy via hydrothermal method [ 12 , 15 ]; and on Mg-Nd alloy by ultrasound-assisted chemical conversion [ 17 ]. CaCO 3 does not pose a threat to any species and is therefore greatly biocompatible [ 18 ] and widely used as a biomaterial in many products, such as toothpaste [ 19 ] and cosmetics [ 20 ], as a vector to deliver drugs, genes, and enzymes [ 21 ], and for controlled degradability in vivo [ 22 ].…”