Corrosion behaviour of plasma electrolytic oxidation coated AZ91 Mg alloy: influence of laser surface melting pretreatment

RSC Advances ◽  
2016 ◽  
Vol 6 (74) ◽  
pp. 70343-70351 ◽  
Author(s):  
Cancan Liu ◽  
Jun Liang ◽  
Jiansong Zhou ◽  
Qingbiao Li ◽  
Zhenjun Peng ◽  
...  
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Corrosion Behaviour ◽  
Surface Melting ◽  
Laser Surface ◽  
Laser Surface Melting ◽  
Mg Alloy ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Plasma electrolytic oxidation (PEO) was performed on a laser surface melting (LSM) modified AZ91 Mg alloy.

scholarly journals Improving Corrosion Resistance of MRI 230D Mg Alloy by Hybrid Coating of Laser Surface Alloying and Plasma Electrolytic Oxidation

2012 ◽  
Vol 706-709 ◽  
pp. 1209-1214 ◽  
Author(s):  
G. Rapheal ◽  
Subodh Kumar ◽  
Carsten Blawert ◽  
Narendra B. Dahotre
Keyword(s):  
Corrosion Resistance ◽  
Plasma Electrolytic Oxidation ◽  
Laser Surface ◽  
Mg Alloy ◽  
Hybrid Coatings ◽  
Corrosion Tests ◽  
Micro Cracks ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Scanning Electron

A permanent mould cast creep resistant MRI 230D Mg alloy was laser surface alloyed (LSA) with Al and Al2O3 in order to improve its wear and corrosion resistance. However, this treatment was successful only in improving wear resistance but not corrosion resistance due to the presence of micro−cracks in the coated layer, which has been discussed in an earlier paper. The LSA coated Mg alloy has been further subjected to plasma electrolytic oxidation (PEO) treatment in alkaline silicate electrolyte in order to cover those micro−cracks and improve corrosion resistance, which is discussed in the present manuscript. For comparison, the PEO coating has also been applied on the as−cast MRI 230D Mg alloy. The microstructural characterization of coatings and corroded surfaces was carried out by scanning electron microscope and X−ray diffraction. Electrochemical corrosion tests were conducted in 3.5 wt% NaCl solution having neutral pH to investigate the corrosion behavior. The LSA coatings consisted mainly of β (Mg17Al12) phase, the coatings produced by PEO treatment on MRI 230D Mg alloy consisted mainly of Mg2SiO4 phase, and hybrid coatings of PEO on LSA consisted of Mg2SiO4 and MgAl2O4 phases in the PEO layer. Scanning electron micrographs of the cross−section revealed that the PEO treatment covered the micro−cracks present in the LSA and corrosion tests revealed that it improved the corrosion resistance, though not to the extent of the corrosion resistance of the PEO coated MRI 230D Mg alloy. All the samples exhibited localized form of corrosion.

scholarly journals Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2094
Author(s):  
Yevheniia Husak ◽  
Joanna Michalska ◽  
Oleksandr Oleshko ◽  
Viktoriia Korniienko ◽  
Karlis Grundsteins ◽  
...  
Keyword(s):  
Cell Culture ◽  
Oxide Layer ◽  
Plasma Electrolytic Oxidation ◽  
Oxide Coating ◽  
Mg Alloy ◽  
Aureus Strain ◽  
Active Surface Area ◽  
Corrosion Properties ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), Photoluminescence analysis and immersion tests were performed to assess structural and long-term corrosion properties of the new coating. Biocompatibility and antibacterial potential of the new coating were evaluated using U2OS cell culture and the gram-positive Staphylococcus aureus (S. aureus, strain B 918). PEO provided the formation of a porous oxide layer with relatively high roughness. It was shown that Ca(OH)2 was a crucial compound for oxidation and surface modification of Mg implants, treated with the PEO method. The addition of Ca2+ ions resulted in more intense oxidation of the Mg surface and growth of the oxide layer with a higher active surface area. Cell culture experiments demonstrated appropriate cell adhesion to all investigated coatings with a significantly better proliferation rate for the samples treated in Ca(OH)2-containing electrolyte. In contrast, NaOH-based electrolyte provided more relevant antibacterial effects but did not support cell proliferation. In conclusion, it should be noted that PEO of Mg alloy in silicate baths containing Ca(OH)2 provided the formation of stable biocompatible oxide coatings that could be used in the development of commercial degradable implants.

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