SEM/EDX, XPS, corrosion and surface roughness characterization of AISI 316L SS after electrochemical treatment in concentrated HNO3

Abstract

In the paper there is described the AISI 316L stainless steel surface obtained after electrochemical treatment in concentrated HNO3. It was characterized by roughness parameters, corrosion protection behaviour and chemical composition of the surface layer. Generally used 2D and 3D roughness parameters describing the surface after the electrochemical treatment are the following: Ra = 0.737 μm and Sa = 1,13 μm as well as Rq = 0,895 μm and Sq = 1,37 μm. In case of corrosion studies the passive current density was equal to 2,3×10 ̶ 2 μA/cm2, pitting potential was equal to Epit = 1140 mV vs. SCE and re-passivation potential was 79 mV vs. SCE. In the surface layer there were detected compounds of iron, chromium, molybdenum, cobalt, manganese, as well as calcium (contamination). The high resolution XPS spectra/results data have shown that most of detected iron compounds can be described as Fe2O3/FeOOH and chromium compounds as Cr2O3/CrOOH. The molybdenum detected in the surface layer was mainly in valency states six (65 at%) and five (17 at%).