A method to monitor corrosion of chromium-iron alloys by monitoring the chromium ion concentration in urine

Abstract

Binary alloys of chromium-iron (Cr-Fe) are no longer used in dental and orthopaedic applications, and were used only for comparative purposes in the present study. Four kinds of Cr-Fe binary alloys, namely, 10 mass%, 15 mass%, 20 mass% and 30 mass%Cr in Fe, and 100%Cr and SUS316L were prepared. These metals were subcutaneously implanted into rats for four months. There was no significant difference in body weights and organ weights among control (sham-operation) and implant-groups, and no significant accumulation of Cr and Fe in the blood, liver or kidney of the alloy implant groups. To clarify the usefulness of urinary monitoring, the Cr and Fe concentrations in rat urine after implantation were analyzed. Alloy implant groups, including the SUS316L group, intended to excrete higher urinary Cr amounts than the control group during the 3 weeks after implantation. Urinary Cr and Fe amounts of the 15%Cr-alloy group showed especially high values in comparison not only with the control level but also the other alloy groups. The visual corrosion extents of the retrieved implants showed the following order: 10%Cr > 15%Cr > 20%Cr > 30%Cr > 100%Cr, SUS316L, and did not always correlate with the levels of the urinary amounts of Cr and Fe. From these findings, monitoring of urinary metal amounts is considered to be useful to monitor the in vivo elution property non-invasively.