Degradationbehaviorof Mg-based biomaterials containing diffe(4)

镁合金,LPSO

Figure5|TheinitiationanddevelopmentofthecorrosionproductsformedontheMDZ-Calloy,(a)afterimmersion10min;(b)30min,(c)60minand(d)120

min.

Cyclicpolarization.Acyclicpolarizationscanprovidesaqualitativeviewofpittingcorrosionmechanismanddeterminesthetrendofundergoingsurfacepittingwhenamaterialisplacedinacorrosivemedium27.ItisparticularlysuitableforMgalloyscontainingLPSOphases,inwhichpittingcorrosionoccursfrequently.ThecyclicpolarizationcurvesoftheMDZ-CandMDZ-545alloysafterdifferenttimeswereshowninFig.7.Thepolarizationcurveswereusedtoestimatethecorrosionpotential(Ecorr),pittingpotential(Epp),andcorrosioncurrentdensity(Icorr)bytheTafel

extrapolationofthecathodicbranches26.Theaveragecorrosionrate(ACR,mmy21)iscalculatedbasedonfollowingequation:

ACR~

IcorrKEw

d

ð1Þ

WhereKisconstantthatdefinestheunitsofthecorrosionrate(,3272mm/A-cm-y).

Ewisequivalentweight(,12g/equivalent).disdensity(,1.7g/cm3

).

Figure6|TheinitiationanddevelopmentofthecorrosionproductsformedontheMDZ-545alloy,(a)afterimmersion10min;(b)30minand(c)60min.