title: [Influence of different NaCl concentration on passive behavior of Cr alloy in vitro].
abstract: OBJECTIVE
  To investigate the properties of passive film of three Cr alloys and to analyze their corrosion resistance in the artificial saliva with different NaCl mass fraction in vitro.
  
  
  METHODS
  Artificial saliva with 1%, 2% and 3% NaCl mass fraction was prepared. Cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy were employed as the working electrode in the artificial saliva. Semi-conductor properties of passive film on Cr alloy was analyzed by Mott-Schottky plots. In addition, the factors which affect the semi-conductive compact characteristic of the passive film was also discussed.
  
  
  RESULTS
  The passive film exhibits n-type semi-conductive characters. With the increasing of NaCl mass fraction, the carrier density of the Cr alloys also increased. The carrier density of the cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy are 3.71 x 10⁸, 2.34 x 10⁹, and 7.66 x 10⁹/cm³ respectively. This decreases its donor density and its film stability.
  
  
  CONCLUSIONS
  When exposed to saliva environment with high concentration of chlorine ion, corrosion resistance of the three types of Cr alloys decrease. This will reduce the service life of Cr alloy prosthesis.
authors.affiliation: Department of Stomatology, Benxi Central Hospital, Benxi Liaoning 117000, China. su1228@163.com
authors.forename: Run-gang
authors.initials: RG
authors.lastname: Su
authors.forename: Shao-feng
authors.initials: SF
authors.lastname: Wang
authors.forename: Xiu-feng
authors.initials: XF
authors.lastname: Zhang
authors.forename: Pei-lin
authors.initials: PL
authors.lastname: Qu
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry*; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D008422:Materials Testing; D012464:Saliva, Artificial; D012965:Sodium Chloride / Q000008:administration & dosage / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D012464:Saliva, Artificial; D012965:Sodium Chloride; D014025:Titanium