Fabrication and corrosion resistance of a hydrophobic micro-arc oxidation coating on AZ31 Mg alloy

Coatings for biodegradable magnesium-based supports for therapy of vascular disease: A general view

Plasma electrolytic oxidation (PEO) is widely used to improve the corrosion resistance and protection of magnesium and its alloys by the formation of ceramic oxide layers. However, this anodization processes generate porous and rough layers with poor tribological properties. In order to improve corrosion protection and tribological capabilities, three different post-treatments (novel sol–gel coating, polytetrafluoroethylene and acrylate-ethylene copolymer with nanoparticles) have been used as sealing agents on PEO anodized AZ91D magnesium alloys. Characterization of unsealed and sealed systems was made by Fourier transform IR (FTIR), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDX) in order to know the chemical structure, morphology and composition of PEO/coating systems. Corrosion resistance was evaluated by electrochemical measurements (open circuit potential and electrochemical impedance spectroscopy) in 5 wt.% NaCl solution at room temperature and by accelerated neutral salt spray test. Tribological properties were obtained using a ball-on-disk test. According to results, post-treatments have improved the corrosion protection performance of PEO systems. However, while internal physical interlocking of pores seemed to be crucial to enhance corrosion protection using polytetrafluoroethylene and sol–gel post-treatments, the formation of an external top layer was the main cause of the improvement of the barrier properties for acrylate–ethylene copolymer post-treatment. On the other hand, despite that tribological performance was mainly governed by the PEO coating, the formation of a top layer on the surface and its chemical composition can significantly reduce the friction coefficient.

Effect of different post-treatments on the corrosion resistance and tribological properties of AZ91D magnesium alloy coated PEO

Three different types of electroless nickel (EN)-phosphorus plating were applied on AZ31 wrought magnesium alloy. The first type was plain mid-phosphorus coating, the second one was duplex, with the first layer having a mid-phosphorus content and the upper one consisting of high-phosphorus whereas the third type of coating was also duplex with a first mid-phosphorus layer and a second high-phosphorus one with incorporated ceramic TiO 2 and ZrO 2 microparticles. Characterization of deposits by means of scanning electron microscopy and X-ray diffraction analysis proves the production of adherent, defect free coatings with differences in crystallinity depending on P content. Surface roughness was maintained at acceptable levels while a great increase in microhardness was observed that was further enhanced by ceramic microparticles incorporation. Electrochemical testing, that was performed by Tafel polarization in 3.5% NaCl solution, show that all the coatings effectively protect the Mg alloy substrate. Additionally, the composite coatings exceptionally enhance the protective capability of the system after heat treatment at 200 °C.

Characterization and corrosion resistance of duplex electroless Ni-P composite coatings on magnesium alloy

Electrodeposition of high corrosion resistance Cu/Ni–P coating on AZ91D magnesium alloy

http://www.ysxbcn.com/down/upfile/soft/2010729/66-p630.pdf

Progress of electroplating and electroless plating on magnesium alloy

Vacuum Pyrolysis of Pine Sawdust to Recover Spent Lithium Ion Batteries: The Synergistic Effect of Carbothermic Reduction and Pyrolysis Gas Reduction

The invention relates to a preparation method of a magnesium alloy surface metal plating layer, which belongs to the technical field of metal corrosion and protection. The method comprises the following steps: (1) carrying out preliminary treatment on the surface of the magnesium alloy; (2) carrying out advanced chemical nickel plating on the surface of the magnesium alloy after the preliminary treatment, wherein an advanced chemical nickel solution is prepared from 15 to 30 g/L of nickel hypophosphite, 5 to 20 g/L of sodium hypophosphite, 8 to 30 g/L of organic coordination agents, 10 to 50 g/L of inorganic coordination agents, 3 to 5 g/L of glycin, 5 to 15 g/L of ammonium hydrogen fluoride, 5 to 10 g/L of sodium acetate, 3 to 5 ppm of potash iodate and 10 to 30 mg/L of dodecyl sodium sulfate, the temperature of the advanced chemical nickel plating is between 50 and 70 DEG C, the pH value is between 7 and 10, and the time is between 30 and 120 min; and (3) carrying out thickening chemical nickel plating or plating other metals on the surface of the magnesium alloy after the advanced chemical nickel plating. The method of the invention improves the combining force of an advanced plating layer and a magnesium alloy base body, and reaches the national standard after the addition of a proper amount of pyrophosphate complexing aids. Metal decorative protective plating layers with strong combining force and high corrosion performance can be obtained after further conventional nickel plating or other metal plating on the advanced chemical nickel plating layer.

Jing-jing Zhao

Papers

Progress of electroplating and electroless plating on magnesium alloy

Vacuum Pyrolysis of Pine Sawdust to Recover Spent Lithium Ion Batteries: The Synergistic Effect of Carbothermic Reduction and Pyrolysis Gas Reduction

Preparation method of magnesium alloy surface metal plating layer

Cathode electrolysis for the comprehensive recycling of spent lithium-ion batteries

NaOH-assisted low-temperature roasting to recover spent LiFePO4 batteries.