Pit initiation on biomedical alloys-A review.

Area of Science:

• Materials Science
• Biomedical Engineering
• Corrosion Science

Background:

• Biomedical alloys possess surface heterogeneities that can initiate pitting corrosion.
• Common biomedical alloys include 316/316L stainless steel, nitinol, and cobalt-chromium (CoCr) alloys.

Purpose of the Study:

• To review and identify specific inclusions acting as pit initiation sites in biomedical alloys.
• To discuss the influence of inclusion type and size on pitting susceptibility in simulated physiological environments.

Main Methods:

• Literature review of studies investigating pitting initiation in biomedical alloys.
• Analysis of inclusion types (sulfide, oxide, carbide, TiN) associated with pitting.
• Correlation of inclusion characteristics with pitting behavior in 316/316L stainless steel, nitinol, and CoCr alloys.

Main Results:

• Sulfide and oxide inclusions initiate pitting in 316/316L stainless steel; sulfide inclusions are predominant.
• Carbide and oxide inclusions initiate pitting in nitinol; carbide inclusions appear more effective.
• Carbides in CoCrMo alloys generally do not initiate pitting unless alloyed with high carbon content or under specific conditions; TiN inclusions in CoNiCrMo may be associated with pits, but repassivation limits pit growth.

Conclusions:

• Inclusion characteristics significantly influence pit initiation in biomedical alloys.
• Understanding these sites is crucial for developing corrosion-resistant biomedical materials.
• Repassivation mechanisms limit pit propagation in certain alloys like CoNiCrMo.