Annotation
Electrochemical Reduction of Corrosion Products on Dental Amalgam SHIGEMJTSU NowuOTO, KUNIHIKO KOBAYASHI, and HIDEO ONOSE Department of Chemistry and Department of Restorative Dentistry, School of Dentistry, Nihon University. 1-8-13 Kanda Surugadai, Chiyodc-ku, Tokyo 101, Japan J Dent Res 56 (10): 1238 October 1977. In order to improve our understanding of the corrosion behavior or electrochemical properties of dental amalgam, a study of the electrochemical reduction of corrosion products formed with anodic polarization by means of linear potential sweep method was undertaken. The polarization curves in the figure are representative for the measurements on set polished Dispersalloy (Johnson & Johnson Co., East Windsor, NJ) with sweep rate 0.1 V/sec in 0.86% NaCl aqueous solution. On the cathodic polarization curve obtained with cathodic potential sweep in the potential region 0.4 V to -1.7 V, three cathodic current peaks (lc to 3c as indicated in the figure) are found. A comparison of the polarization curves obtained as a function of the potential sweep region reveals that these ic, 2c, and 3c are associated with the reduction of the corrosion products formed during the anodic potential sweep around the region la, 2a, and 3a. Peak lc is probably caused by the reduction of CuCl formed at about region la and a graphical integration of the polarization curves yields 24 mcoul/cm2 for peak lc under the conditions of this experiment. Peak 2c may be due Received for publication March 23, 1977. Accepted for publication April 15, 1977. i14 lc
to the reduction of Sn (IV) compound (SnO2 etc.) formed at peak 2a during the anodic polarization, and the charge corresponding to peak 2c is about 40 mcoul/cm2 determined by the graphical integration. This amount of the charge is somewhat lower than that of peak 2a; therefore it is suggested that the anodic peak current 2a involved dissolution current of Sn (SARKAR and GREENER, J Dent Res, 51:1675, 1972). Peak 3c is caused by the reduction of Sn(II) compound (SnO, Sn(OH)2, Sn(OH)CI) formed in the anodic sweep region 3a and it yields about 24 mcoul/cm2 under these conditions. These peak currents are increased with potential sweep rate but not linear to it and hence the reduction amounts are changed with the sweep rate as a result of the change of oxide amounts formed during the anodic sweep. The peak potentials shift to cathodic or anodic direction with increase of sweep rate of cathodic or anodic potential sweep because of overvoltages. These results indicate that the corrosion products on the dental amalgam are reduced separately at distinct potentials and we may estimate the species and the amount of the corrosion products by means of the polarization curves; hence this technique will be useful for elucidation of oxide film formation or corrosion of dental amalgam under various conditions and such a study has been initiated in this laboratory.
3c
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2c
C)
E
3a
- / cs .fd
/
2a
00
-
0.5
-
1.0
E V(sce)] E Polarization Curves for Dispersatloy in 0.860/o NaCl, Sweep rate 0.1 Y'sec Electrode Area 0.126cm2,
1238 Downloaded from jdr.sagepub.com at NORTH DAKOTA STATE UNIV LIB on May 31, 2015 For personal use only. No other uses without permission.
Electrochemical Reduction of Corrosion Products on Dental Amalgam SHIGEMJTSU NowuOTO, KUNIHIKO KOBAYASHI, and HIDEO ONOSE Department of Chemistry and Department of Restorative Dentistry, School of Dentistry, Nihon University. 1-8-13 Kanda Surugadai, Chiyodc-ku, Tokyo 101, Japan J Dent Res 56 (10): 1238 October 1977. In order to improve our understanding of the corrosion behavior or electrochemical properties of dental amalgam, a study of the electrochemical reduction of corrosion products formed with anodic polarization by means of linear potential sweep method was undertaken. The polarization curves in the figure are representative for the measurements on set polished Dispersalloy (Johnson & Johnson Co., East Windsor, NJ) with sweep rate 0.1 V/sec in 0.86% NaCl aqueous solution. On the cathodic polarization curve obtained with cathodic potential sweep in the potential region 0.4 V to -1.7 V, three cathodic current peaks (lc to 3c as indicated in the figure) are found. A comparison of the polarization curves obtained as a function of the potential sweep region reveals that these ic, 2c, and 3c are associated with the reduction of the corrosion products formed during the anodic potential sweep around the region la, 2a, and 3a. Peak lc is probably caused by the reduction of CuCl formed at about region la and a graphical integration of the polarization curves yields 24 mcoul/cm2 for peak lc under the conditions of this experiment. Peak 2c may be due Received for publication March 23, 1977. Accepted for publication April 15, 1977. i14 lc
to the reduction of Sn (IV) compound (SnO2 etc.) formed at peak 2a during the anodic polarization, and the charge corresponding to peak 2c is about 40 mcoul/cm2 determined by the graphical integration. This amount of the charge is somewhat lower than that of peak 2a; therefore it is suggested that the anodic peak current 2a involved dissolution current of Sn (SARKAR and GREENER, J Dent Res, 51:1675, 1972). Peak 3c is caused by the reduction of Sn(II) compound (SnO, Sn(OH)2, Sn(OH)CI) formed in the anodic sweep region 3a and it yields about 24 mcoul/cm2 under these conditions. These peak currents are increased with potential sweep rate but not linear to it and hence the reduction amounts are changed with the sweep rate as a result of the change of oxide amounts formed during the anodic sweep. The peak potentials shift to cathodic or anodic direction with increase of sweep rate of cathodic or anodic potential sweep because of overvoltages. These results indicate that the corrosion products on the dental amalgam are reduced separately at distinct potentials and we may estimate the species and the amount of the corrosion products by means of the polarization curves; hence this technique will be useful for elucidation of oxide film formation or corrosion of dental amalgam under various conditions and such a study has been initiated in this laboratory.
3c
-
2c
C)
E
3a
- / cs .fd
/
2a
00
-
0.5
-
1.0
E V(sce)] E Polarization Curves for Dispersatloy in 0.860/o NaCl, Sweep rate 0.1 Y'sec Electrode Area 0.126cm2,
1238 Downloaded from jdr.sagepub.com at NORTH DAKOTA STATE UNIV LIB on May 31, 2015 For personal use only. No other uses without permission.
