Table 2.

Reports on corrosion resistance of Mg and its alloys.

Material and method	Findings
Calcium addition to AZ91Ca (1 wt%) and AZ61 (0.4 wt%) alloys [81]	The high amount of Ca in the alloy enhanced the formation of calcium phosphate on the surface and improved corrosion resistance; there was only a slight decrease in mechanical property of the alloy in SBF as compared to that of in air
Mg-Mn and Mg-Mn-Zn alloys [82]	Addition of Mn and Zn elements accelerated the formation of Mg-containing phosphate and provided better protection for matrix alloy; Zn-containing phosphate layer provided an effective protection to the alloy
Alkaline heat treatment on Mg-Ca alloy [83]	Corrosion rates of treated alloy in SBF were decreased; the treated alloy samples did not induce toxicity to L-929 cells during 7 days of culture
MgF2 coating on extruded LAE442 alloy [84]	Extruded LAE442 alloy provided low corrosion rates and reacts in vivo with an acceptable host response; localized corrosion attack was observed in both coated and uncoated LAE442 implants
Hydroxyapatite coating on AZ91 alloy [85]	The coated alloy showed 20% improvement in the mechanical strength as compared to that of the uncoated one; 40% loss in the mechanical strength after 5 days of exposure to SBF was measured for the uncoated alloy
Hydroxyapatite coating with MgF2 interlayer on pure Mg [86]	Coated Mg corroded less than bare Mg and showed an effective protection from in vivo corrosion; coated Mg had a higher bone-to-implant contact ratio in the cortical bone area of the rabbit femora 4 weeks after implantation
Phosphating treatment to form brushite layer on extruded Mg-Mn-Zn alloy [81, 87]	Electrochemical and immersion tests showed that the brushite (CaHPO4·2H2O) coating provided a good protection against corrosion in SBF; corrosion resistance increased with the increase of the phosphating time within 50 min
Chitosan coating on Mg-1Ca alloy [88]	Corrosion resistance of the coated alloy in SBF was improved