Effect of Synthesizing Temperature on Microstructure and Electrochemical Property of the Hydrothermal Conversion Coating on Mg-2Zn-0.5Mn-Ca-Ce Alloy

Abstract

Mg(OH) 2 conversion coatings were formed on an Mg-2Zn-0.5Mn-Ca-Ce alloy via hydrothermal method at three different synthesizing temperatures (160, 170 and 180˝C). The effect of synthesizing temperature on microstructure and electrochemical property of the coatings were systematically studied. With increasing synthesizing temperature, the coating became thicker due to the faster reaction and deposition of Mg(OH) 2 on the α-Mg phase and secondary phases of the substrate Mg alloy. Internal micro-cracks were also generated in the higher-temperature synthesized coatings due to the increased shrinking stress, but the cross-cutting micro-cracks were suppressed. Benefiting from the improved barrier effect against penetration of corrosive medium, the higher-temperature synthesized thicker coating presented significantly enhanced electrochemical property and anti-corrosion efficiency in Hanks' solution.

Structure and Physical Properties of NiO/Co3O4 Nanoparticles

“…The acquirement of the desired physical and chemical properties from metal oxide NPs requires an effective preparation method and has become a significant subject of research. There are several nonconventional techniques in order to achieve high quality metal oxide nanoparticles that have been used or are under development for preparing ultrafine nanostructures [7][8][9][10][11][12][13][14][15][16][17][18]. Numerous factors and various precipitation agents were utilized to synthesis magnetic metal oxide nanocrystals with specific structures.…”

Decreasing Bio-Degradation Rate of the Hydrothermal-Synthesizing Coated Mg Alloy via Pre-Solid-Solution Treatment

“…The coating fails to fulfill its protective functionality after such penetration no matter how thick it is. The formation of such defective coating is closed related to the secondary phase distribution and morphology [ 29 , 30 ]. After pre-SS treatment of the substrate, the disappearing of secondary-phase net-like structure and decrease in volume fraction was achieved, and the net-like cracks of the coating were suppressed accordingly.…”

“…It exhibited an improved corrosion resistance, while its bio-degradation rate was still not up to medical standards. An effective approach to reduce the bio-degradation rate of such an alloy was to hydrothermally synthesize a protective Mg(OH) 2 coating [ 29 ]. However, the secondary phases of the Mg–2Zn–Mn–Ca–Ce alloy was found to deteriorate the coating compactness, leading to continuous micro-cracks on the coating layer [ 30 ].…”

Developing Improved Mechanical Property and Corrosion Resistance of Mg-9Li Alloy via Solid-Solution Treatment

“…Meanwhile, the SS alloy kept a continuous slow increase in OCP value during the whole tested immersion period, indicating the superior stability of the surface film. EIS is widely used in the investigation of electrochemical corrosion behavior of metallic materials, which has a great advantage in continuously monitoring the evolution of corrosion characteristic [58][59][60]. Figure 6a and b are the EIS Nyquist plots of the tested alloys obtained from the different immersion periods in the 0.1 mol/L NaCl solution.…”