Corrosion process of stainless steel in natural brine as a source of chromium and iron – the need for routine analysis

Abstract

The corrosion of the installations carrying high salinity water is particularly important in the case of utility and therapeutic waters, such as natural brine. The analysis of such complex systems is challenging in the context of routine analysis of Fe and Cr. Both elements can be determined by UV-Vis spectrophotometry after only 1 : 100 dilution and liquid–liquid extraction (LOD_Fe = 0.03 mg L⁻¹) or thermal chloride stripping (LOD_Cr = 0.02 mg L⁻¹). The corrosion process was characterized. Electrochemically accelerated corrosion showed uneven decomposition of the steel components – Cr is less easily released to the solution than Fe. Iron comprises 53% of the dissolved part, and Cr comprises 8.6%, while the steel originally contained 62% of Fe and 18% of Cr. During the short-term (one week) contact of the brine with stainless steel, the amounts of Fe and Cr released to the brine were insignificant from the perspective of its therapeutic value.