Experimental Study On The Corrosion Resistance Of Nicr Alloy With Nano-amorphous Diamond Film

Objective:By employing the electrochemical corrosion method, we evaluated theresistance of nickel-chromium alloy plated with amorpHous diamond filmagainst corrosion under different conditions, such as various pH value or NaFconcentrations in artificial saliva at36.5°C. Our purpose of this experimentis to explore the possibility of dental nickel-chromium alloy modified.Methods:48nickel-chromium alloy cyinder specimens were cast and turned on alathe,each was30mm in length and3mm in diameter, and there was no visibledeformation or voids. The surface of each specimen was ground down using400,600,800meshes, and then be polished well with metallograpHical sandpaper in the order of400,800,1200meshes. Randomly assign the preparedspecimens into two groups: group A and group B. Group A as experimentalgroup, in this group,8minutes was used in nanometers amorphous diamondfilm forming on the surface of each specimens, which was50nm thick, byusing chemical vaporous depositon （CVD） method at room temperature.While group B as control group, there was no more preparation for thespecimens in this group. All specimens were sealed with epoxy resin expeptthe cross-section of both the end. One cross-section is for joining the wire,and the other standby （area of7.065mm2）. Wipe the surface of the standbycross-section with95%ethanol and dip into artificial saliva for20minutes tostabilize the surface of the specimen.The test conditions:6groups was divided according to different artificialsaliva: group a （pH6.8, no NaF）; group b （pH6.8,0.1%NaF）; group c （pH6.8,0.2%NaF）; group d （pH4.0, no NaF）; group e （pH4.0,0.1%NaF）; group f（pH4.0,0.2%NaF）. Electrochemical analysis: the initial surface potential （Ecorr）, Tafel curveand the corrosion current （Icorr） were also evaluated in this experiment.Results:1The potential of corrosion （mv）1.1By comparing the Ecorr of plated specimens and unplated specimens, wefound that in group a, d, e, f, E_Ais significantly higher than E_B（P <0.05）; ingroup b and c, there is no statistic difference between E_Aand E_B（P>0.05）.1.2At the same pH condition, we compared the impact of F—on the Ecorr ofplated and unplated specimens.At pH6.8（group a, b, c）, for both plated and unplated specimens, E_a＞E_b＞E_c. The difference among3different conditions is significant （P<0.05）. But the concentration of F—（group b and c） does not influence Ecorr（P>0.05）.At pH4.0（group d, e, f）, for both plated and unplated specimens, there isno statistic significance of Ecorr with varied concentrations of F—.（P>0.05）1.3At the same concentration of F—, we compared the impact of pH on theEcorr of the plated and unplated specimens.For all the concentrations of F—: group a and d （no NaF）, group b and e（0.1%NaF）, group c and f （0.2%NaF）, there is no statistic significancebetween Ecorr at pH6.8and Ecorr at pH4.0, either plated or unplatedspecimens.（P>0.05）2Corrosion current density I（μA/cm²）2.1By comparing the I of plated specimens and unplated specimens, wefound that in group b, d, and f, I（A）is significantly lower than I_B（P <0.05）; ingroup a, c, and e, there is no statistic difference between I_Aand I_B（P>0.05）.2.2At the same pH condition, we compared the impact of F—on the I ofplated and unplated specimens.At pH6.8（group a, b, c）, for both plated and unplated specimens, I_a<I_b<I_c. The difference among3different conditions is significant （P <0.05）.But the concentration of F—（group b and c） does not influence I （P>0.05）.At pH4.0（group d, e, f）, for both plated and unplated specimens, there is no statistic significance between I with varied concentrations of F—.（P>0.05）2.3At the same concentration of F—, we compared the impact of pH on the Iof the plated and unplated specimens. For all the concentrations of F—:group a and d （no NaF）, group b and e （0.1%NaF）, group c and f （0.2%NaF）,there is no statistic significance between I at pH6.8and I at pH4.0, eitherplated or unplated specimens.（P>0.05）Conclusion:1The Ecorr and Icorr results of experimental group and control indifferent F—and in different pH value artificial saliva, shows that: thecorrosion potential in experimental group is higher than in control, thissuggests the corrosion resistance could be improved by platingnickel-chromium alloy with amorphous diamond film.2With the increase of F—, the corrosion resistance of the specimens isreduced3With the decrease of pH value, the corrosion resistance of thespecimens is reduced.