Corrosion behavior of AISI 316L borided and non-borided steels immersed in a simulated body fluid solution

The corrosion resistance of AISI 316 L borided and non-borided steels was evaluated during 10 days of immersion in a simulated body fluid (Hanks' solution). The FeB/Fe₂B layer was developed using the powder-pack boriding process at 1223 K and 6 h of exposure. First, the electrochemical behavior on the surface of borided and non-borided steels was assessed using Electrochemical Impedance Spectroscopy, EIS. After the corrosion tests, the surface of both types of samples were analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectrometry (EDS) and X-Ray Photoelectron Spectroscopy (XPS), to establish the corrosion mechanisms, the composition and the electrochemical species developed over the surface, after 10 days in the simulated body fluid solution (SBFS), respectively. According to the electrochemical study, the AISI 316 L borided steel provided a reasonable corrosion resistance notwithstanding, the non-borided steel exhibited higher resistance values. Finally, it was concluded that the decrease of corrosion resistance of AISI 316 L borided steel was caused by a rather complex combination of chemical interactions amongst boron-bearing species, sulfates and phosphates taking place initially over the borided surface and subsequently through pits and cracks after 10 days of immersion in Hanks' solution.