Surface Properties Of Cobalt-chromium Alloy By Different Polishing Methods

Objective:The purpose of this study was to investigate the effect of following different polishing methods:traditional polishing, electropolishing, and chemical polishing on the surface morphology, corrosion behavior, Actinomyces viscosus adhesion resistence of cobalt-chromium alloy,by using scanning electron microscopy(SEM), electrochemical test, and Actinomyces viscosus adhere test.Method:ExperimentⅠ:20 cobalt-chromium alloy specimens without obvious defects were randomly divided into 4 groups,then they were finished by a mechanical grinding device with 280 to 600 grit silicon carbide papers to eliminate surface irregularities. Different groups of specimens were polished separately by traditional polishing,electro- polishing, or chemical polishing,specimens without polishing as contrast.After polishing,SEM was used to analyzed the surface microstructure of different groups. Then specimens of 4 groups were immersed into the artificial saliva for 2 weeks with constant temperature(37.0℃),then electrochemical experiment was carried out for each specimen,and the surface microstructure of each group was observed again.Experiment II:32 cobalt-chromium alloy specimens without obvious defects were randomly divided into 4 groups,finishing and polishing methods were same with Experiment I.Actinomyces viscosus were raised on each specimen's surface of the other 4 groups for 48h,then calculated the amount of adhesive Actinomyces viscosus,to analyze the Actinomyces viscosus adhesion resistence of each group.Results:(1)SEM:After polishing,there are a lot of deep scratches on the surface of the control group. Hand-polished group significantly reduced the surface scratches and there are only a little shallow scratches.Much prominent irregular insoluble phase in the matrix of the hand-polished group was found. The chemical polishing group has lots of scratches too,but the scratches are shallower.(2)SEM:after artificial saliva immersion, there was visible corrosion pit holes and corrosion products of the control group, hand-polished group did not change significantly,there were lots of corrosion products on the surface of electrolytic polishing group,for chemical polishing group, the erosion appearance was on the edge of scratches,the dent of part scratches seemed to be deepened.(3)Both the Ecorr and Icorr were the largest for control group, followed by electrolytic polished group and chemical polished group,there was no significant difference between the two groups, hand-polished group had the minimum Ecorr and Icorr.(4)The control group and electrolytic polishing group had the largest number of Actinomyces viscosus adhesion,there was no significant difference between them, followed by chemical polishing group, hand-polished group of Actinomyces viscosus adhesion was the least.Conclusion:(1)Under the experimental condition,for cobalt-chromium alloy, corrosion resistance and anti-adhesion properties of Actinomyces viscosus were significantly improvement after traditional polishing;by chemical polishing, the two properties were improved to some extent; electropolishing had improved corrosion resistance, but it could not reduce the surface adhesion amount of Actinomyces viscosus.(2)Under the experimental condition,hand-finishing is better than electro-polishing, chemical polishing in corrosion resistance and anti-bacterial adhesion.