New generation super alloy candidates for medical applications: Corrosion behavior, cation release and biological evaluation

• Evaluation of a super austenitic steel, in the perspective of a medical application
• 316L and 904L are not resistant to corrosion and abrasion in contact with skin.
• Alloys studied were chosen to surpass these two alloys.
• Nickel released in super austenitic steel did not conform to EU legislation.
• The super alloys studied cannot be proposed for articles in contact with the skin.

Three super alloy candidates (X1 CrNiMoMnW 24-22-6-3-2 N, NiCr21 MoNbFe 8-3-5 AlTi, CoNiCr 35-20 Mo 10 BTi) for a prolonged contact with skin are evaluated in comparison with two reference austenitic stainless steels 316L and 904L. Several electrochemical parameters were measured and determined (Eoc, Ecorr, icorr, ba, bc, Eb, Rp, Ecrev and coulometric analysis) in order to compare the corrosion behavior. The cation release evaluation and in vitro biological characterization also were performed.In terms of corrosion, the results reveal that the 904L steels presented the best behavior followed by the super austenitic steel X1 CrNiMoMnW 24-22-6-3-2 N. For the other two super alloys (NiCr and CoNiCr types alloys) tested in different conditions (annealed, work hardened and work hardened + age hardened) it was found that their behavior to corrosion was weak and close to the other reference stainless steel, 316L. Regarding the extraction a mixture of cations in relatively high concentrations was noted and therefore a cocktail effect was not excluded. The results obtained in the biological assays WST-1 and TNF-alpha were in correlation with the corrosion and extraction evaluation.