Stress Corrosion Cracking and Corrosion Fatigue of Some Surgical Implant Materials in a Physiological Saline Environment Available to Purchase

The results of slow strain rate tensile tests and concomitant fractography suggest that cast Vitallium and Type 316L stainless steel, which are widely used for surgical implants, are not susceptible to stress corrosion cracking (SCC) in a physiological saline (Tyrode’s) solution. Several high strength, high ductility stainless steels (TRIP steels), which are candidates for implant use, also appeared to be immune to SCC. Some combinations of TRIP steel composition and metallurgical condition showed significantly lower elongations to failure in Tyrode’s solution than in air, but no fractographic evidence of SCC was obtained. The susceptibilities to corrosion fatigue of cold worked Type 316L and two TRIP steels were assessed by comparing the fatigue lives of smooth specimens tested in argon and Tyrode’s solution. All three materials generally showed lower fatigue lives in the saline environment, the degree of life reduction being dependent on electrochemical potential. Although additional research is needed, the present data suggest that TRIP steels are capable of supporting substantially higher levels of static and cyclic stress in saline environments than the materials now being used for metallic surgical implants.