title: Effect of heat history on the corrosion of ferritic stainless steels used for dental magnetic attachments.
abstract: This study investigated the effect of heat history on the corrosion of keepers used for dental magnetic attachments. Ferritic stainless steels of SUS 444 and 447J1 were prepared with heat treatments in the temperature range of 550-850 degrees C for 1-5 hours. The stainless steels were electrochemically and metallurgically examined by anodic polarization curves in a 0.9% NaCl solution and by microstructural observation using an electron probe microanalyzer with WDS. Heating both kinds of stainless steel at 650-750 degrees C for two hours or more led to the deterioration of their corrosion resistance. For example, there was evidence of a reduction in the breakdown potentials and an increase in the current densities of the anodic polarization curves. These phenomena were attributed mainly to the precipitation of the sigma (FeCr) or chi (Fe18Cr6Mo5) phase, which sometimes resulted in intergranular corrosion. When dental alloys are cast in investment molds embedding the keepers, the heat time required for thermal expansion of the molds should be kept under one hour.
authors.affiliation: Division of Dental Biomaterials, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan. takada@mail.tains.tohoku.ac.jp
authors.forename: Yukyo
authors.initials: Y
authors.lastname: Takada
authors.forename: Osamu
authors.initials: O
authors.lastname: Okuno
mesh_terms: D002857:Chromium / Q000737:chemistry; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D004563:Electrochemistry; D004577:Electron Probe Microanalysis; D005290:Ferric Compounds / Q000737:chemistry*; D006358:Hot Temperature; D006801:Humans; D007501:Iron / Q000737:chemistry; D008280:Magnetics / Q000295:instrumentation*; D008422:Materials Testing; D008669:Metallurgy; D008982:Molybdenum / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry*; D013997:Time Factors
chemical_list: D003722:Dental Alloys; D005290:Ferric Compounds; D002857:Chromium; D013193:Stainless Steel; D012965:Sodium Chloride; D008982:Molybdenum; D007501:Iron