Location of cobalt impurities in the surface oxide of stainless steel 316L and metal release in synthetic biological fluids. (March 2022)

• Record Type: Journal Article
• Authors: Wang, Xuying; Hedberg, Jonas; Nie, Heng-Yong; Biesinger, Mark C.; Odnevall, Inger; Hedberg, Yolanda S.
• Is Part Of: Materials & design. Volume 215(2022)
• Publication Date: 2022-03
• Subjects: Stainless steel -- Cobalt -- ToF-SIMS -- XPS -- Passive films -- Bioaccessibility; ALF Artificial Lysosomal Fluid -- BE Binding Energy -- Co Cobalt -- Fe Iron -- GST Artificial Gastric Fluid -- ICPMS Inductively Coupled Plasma Mass Spectrometry -- IMFP Inelastic Mean Free Path -- LOD Limit of Detection -- LOQ Limit of Quantification -- Mn Manganese -- Mo Molybdenum -- Ni Nickel -- PBS Phosphate Buffered Saline -- REACH Registration, Evaluation, Authorisation and Restriction of Chemicals -- ToF-SIMS Time of Flight Secondary Ion Mass Spectrometry -- XPS X-ray Photoelectron Spectroscopy; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2022.110524
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Bioaccessibility of cobalt in stainless steels important from a legislative view. Surface oxide and metal release of austenitic stainless steel 316L studied. Metallic cobalt homogeneously co-located with nickel beneath the surface oxide. Cobalt traces released with other metals upon surface reformation and passivation. Surface enrichment of cobalt due to precipitation of released cobalt in PBS. Abstract: Since 2021, cobalt (Co) is in Europe classified as carcinogen in quantities exceeding 0.1 wt-%. This affects nickel-rich stainless steels, which contain about 0.2 wt-% Co impurities. Previous findings show the bioaccessibility of Co in stainless steel to be primarily determined by the corrosion resistance. It has been unclear whether Co is distributed heterogeneously in the alloy and the outermost surface and whether a specific location would pose a risk for Co release under specific exposure conditions. This study aimed at locating Co in stainless steel 316L (0.2 wt-% Co) surfaces prior to and after exposure to different synthetic body fluids for 24 h at 37 °C. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICPMS) investigated the location of Co in the surface oxide and extent of release along with other metals (iron, chromium, nickel, and manganese) into synthetic biological fluids (gastric fluid, pH 1.5; lysosomal fluid, pH 4.5; phosphate buffered saline-PBS, pH 7.4). Co was homogeneously distributed along with metallic nickel beneath the surface oxide and co-released with other metals upon surface reformation and passivation. Exposure in PBS resulted in the incorporation of both Co and phosphate in the oxide.