Surgical implants pitting

Pitting and stress corrosion cracking, although usually associated with stainless steels in chloride media, have not been observed on recovered surgical implants. Implants often exhibit cracks and surface pitting, but these are most likely the result of improper manufacture rather than corrosion . 

The test method ASTM F7464 covers the determination of the resistance to either pitting or crevice corrosion of passive metals and alloys from which surgical implants are produced. The resistance of surgical implants to localized corrosion is carried out in dilute sodium chloride solution under specific conditions of potentiodynamic test method. Typical transient decay curves under potentiostatic polarization should monitor susceptibility to localized corrosion. Alloys are ranked in terms of the critical potential for pitting, the higher (more noble) this potential, the more resistant is to passive film breakdown and to localized corrosion. (Sprowls)14... 

F746-87, Standard test method for pitting or crevice corrosion of metallic surgical implant materials. Annual Book of ASTM Standards, ASTM International, Philadelphia, Pa., 2000, p. 203, Vol. 13.01. 

ASTM F 746, Test Method for Pitting or Crevice Corrosion of Metallic Surgical Implant Materials. 

ASTM F 746 Standard Test Method for Pitting or Crevice Corrosion of Metallic Surgical Implant Materials Measurement of pitting or crevice tendency by measuring repassivation tendency after polarization at noble potential. Applicable only to passive alloys. 

Electrochemical techniques have also been used to provide a rapid test in ASTM F 746, Test Method for Pitting or Crevice Corrosion of Metallic Surgical Implant Materials. A specimen is anodically p>olarized to stimulate pitting and then returned to a less positive preset potential to determine if repassivation will occur. This is repeated at successively higher preset potentials until the final, or criticcJ potential is determined. More resistcmt materitJs display higher critical potentials. This relatively brief test does not wait for pits to initiate tmd reduces variabiUty by maintaining the potential of the specimen. 

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