[The effect on anti-acid corrosion resistance of Ni-Cr alloy coating titanium].
OBJECTIVE
The aim of this study was to investigate the variation of the corrosion resistance of Ni-Cr alloy in acid environment before and after coating titanium in vitro.


METHODS
1. Surface treatment using sol-gel technique of coating titanium. The steps were as follows: (1) Pre-treatment: sanding, washing and activation in order to remove the oxidative product; (2) The preparation of sol: some small charged particles produced by the hydrolytic reaction, and formed sol. These particles would congeal into extremely small ones (diameter usually is 5 microns); (3) Coating; (4) Heat treatment: The organism was resolved and volatilizeed at high temperature, and the atoms of Ti were left. These atoms of Ti were very active and could combine firmly with the atoms on the surface awaiting of treatment. 2.


CONCLUSIONS
artificial saliva; pH = 7.0 and pH = 5.6; temperature: 36.5 degrees C 3. Electrochemical test: polarization curve; instrument: ZF-3 poteniostat.


RESULTS
Before coating titanium, when pH was 7.0, the electrode potential of Ni-Cr alloy was -160 mV, and the self-corrosion current density was 0.262 microA cm-2; when pH = 5.6, the data were -182 mV and 0.352 microA cm-2, respectively. This result showed that when pH value reduced, the potential and current density descended, too. This indicated that the material was easy to be corroded. After coating titanium, when pH value was 7.0, the potential was -71 mV, the self-corrosion current density was 0.152 microA cm-2; when pH = 5.6, the data were -89 mV and 0.174 microA cm-2. This indicated that the corrosion rate of material descended evidently after coating titanium in acid environment.


CONCLUSIONS
(1) Not only before coating Ti but also after coating, the corrosion resistance of Ni-Cr alloy would descend in acid environment;(2) In acid environment, the corrosion resistance of Ni-Cr alloy after coating titanium was superior to that of the material before coating. So was in neutral environment.
Hu
Bin
B
Department of Prosthodontics, School of Stomatology, Ninth People's Hospital, Shanghai Second Medical University, Shanghai 200011, China.
Zhang
Fu-qiang
FQ
D002857:Chromium / Q000737:chemistry*; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
D003722:Dental Alloys; D002857:Chromium; D009532:Nickel; D014025:Titanium