Effect of alloying elements on the electronic properties of thin passive films formed on carbon steel, ferritic and austenitic stainless steels in a highly concentrated LiBr solution

The influence of alloying elements on the electrochemical and semiconducting properties of thin passive films formed on several steels (carbon steel, ferritic and austenitic stainless steels) has been studied in a highly concentrated lithium bromide (LiBr) solution at 25 °C, by means of potentiodynamic tests and Mott-Schottky analysis. The addition of Cr to carbon steel promoted the formation of a p-type semiconducting region in the passive film. A high Ni content modified the electronic behaviour of highly alloyed austenitic stainless steels. Mo did not modify the electronic structure of the passive films, but reduced the concentration of defects

Effect of temperature on the passive state of Alloy 31 in a LiBr solution: Passivation and Mott-Schottky analysis

The passive behaviour of Alloy 31, a highly‐alloyed austenitic stainless steel (UNS N08031), has been investigated in a LiBr heavy brine (700 g/l) at different temperatures using potentiostatic polarisation and Mott‐Schottky analysis. Cation vacancies have been found to be the dominant defect in the passive films formed on Alloy 31. An increase in temperature enhanced the generation of cation vacancies at the film/solution interface and raised the steady‐state passive current density. The density of defects within the passive film also increased significantly with temperature, making the film more conductive and less protective against localised attacks

Revealing the superior corrosion protection of the passive film on selective laser melted 316L SS in a phosphate-buffered saline solution

This study investigated the passivation behaviour of wrought 316L stainless steel (SS) and 316L manufactured by the Selective Laser Melting (SLM) process in phosphate-buffered saline (PBS). The 3D printing laser power influenced microstructure, passive film and corrosion resistance of SLM 316L SS were studied, and compared with the results of wrought 316L SS. The results indicated that a smaller corrosion current density and improved breakdown potential (Eb) of SLM 316L SS was associated with a higher proportion of Cr2O3 in the passive film at OCP conditions. The Transmission Electron Microscopy (TEM) proved that the passive film on SLM 316L SS was continuous and compact at 600 mV vs. Ag/AgCl applied potential. The increase in the applied potential resulted in a high content of hydroxide being recorded in the passive film. The results also suggest preferential facets of (1 1 0) and abundant grain/sub-grain boundaries for SLM 316L SS, as well as the increased work of separation and growth rate of the passive film from the substrate. Wrought 316L SS demonstrated preferred facets of (1 1 1)-γ and larger grains. There are confirmed via X-Ray Diffraction (XRD), Electron Backscatter Diffraction (EBSD) and the first-principle calculation