Potentiodynamic-Polarization and Electrochemical-Impedance Study of Cast and Laser-Sintered Alloys

There are many systems using CAD/CAM technology for rapid production of PFM. Selective laser sintering of alloys is one of these technologies. Objectives: To compare the electrochemical corrosion behavior of two conventionally cast dental alloys (Ni-Cr and Co-Cr) with laser-sintered (Co-Cr) alloy. Methods: Test samples (N=5) were disks with 11mm diameter and 3mm thickness prepared according to ISO-10271. The potantiodynamic potential range between -1000/+1000mV (CH Instrument 660 C) was performed in Fusayama artificial saliva (Ph=4.9). Cyclic voltmmograms (CV) values were monitored between +0.5/-0.5 volts from the open circuit potential that showed the Potential(V)–Current(A) graphs. All electrodes were performed with electrochemical impedance spectroscopy between 10+5/10-2 hertz. Results: Open circuit potential of laser sintered Co-Cr alloy (-0.327/-0.188V) was similar to Co-Cr cast alloy (-0.325/-0.184V), but lower than Ni-Cr alloy (-0.211/-0.157V). The Eocp value of laser-sinter specimens was lower than Co-Cr alloy and they were more resistant to cast Co-Cr alloy. When the potential was between 0.4/0.8V, a plateau was observed for all three groups, yet, at different anodic current values; -4.0/-3.8A, -4.8/-3.4A, and -4.0/-3.5A for Ni-Cr alloy, cast Co-Cr, and laser sintered Co-Cr alloy, respectively. Ni-Cr alloy showed significant differences from cast Co-Cr alloy. However, only minor differences were observed between cast Ni-Cr and laser sintered Co-Cr alloys. These results confirmed the selective laser sintering procedure reduces the effect of cobalt EO value. For the sintering procedure the anodic current values was lower than it was for the casting method. According to the logarithmically given CV, the potentials corresponding to zero current at backward scan were similar for laser sintered (-0.05V) and cast Ni-Cr (-0.05 V) specimens, but different from cast Co-Cr (-0,2V) alloy. The electrochemical impedance spectroscopic evaluations supported the potantiodynamic evaluations. Conclusions: Laser sinter procedure increases the nobility of Co-Cr alloy and seems promising with a good corrosion behavior.