(Morris Cohen Graduate Student Award of the Corrosion Division) Stainless Steel in Biological Environments – Relation Between Material, Surface Chemistry and Toxicity

Stainless steels are commonly used in a variety of essential applications in our daily-life, for instance as biomaterials and in food contact applications. Even though the corrosion resistance of such grades is high, or very high, alloy components will be released to different extent in contact with biological media of varying composition, acidity and metal complexation capacity, a process that may induce adverse toxicological effects. Research activities have focused to quantitatively determine, and kinetically and mechanistically assess the metal release process in relation to material and surface properties of stainless steels of different grade as massive sheet and as powders in contact with biological systems of relevance for human exposure. Surface-protein interactions have been addressed from a combined surface chemistry, corrosion and material science and toxicological approach. Generated findings clearly show that both bulk and surface oxide properties such as phase, structure, morphology, chemical and electrochemical stability, largely influence the metal release process, biointerfacial interactions, bioavailability of released metals, and subsequent toxicity. For example, the cooling-rate dependent surface oxide speciation (surface oxide thickness, composition, phase and phase distribution, crystallinity etc.) of stainless steel particles strongly determines whether the dominant mechanism of metal release in complexing biological environments is corrosion-controlled or ligand-induced chemical dissolution. Research findings are of vital importance for risk assessments of stainless steel and alloys, to understand adsorption phenomena on stainless steel, metal release and corrosion processes, and the influence of surface oxide speciation on metal release, corrosion, and toxicity.