Microstructure Characteristic and Electrochemical Corrosion Behavior of Surface Nano-crystallization Modified Carbon Steel

The surface nano-crystallization (SNC) of carbon steel was achieved via a high-speed rotating wire-brushing process. Microstructure characteristics of SNC steel were systematically studied. The SNC steel surface exhibited marked deformed plastic flows and high surface roughness. Due to the accumulated strains, a deformed gradient layer with thickness of 40-50 mu m was produced, and the grain size of the topmost zone was about 50-100 nm. X-ray photoelectron spectroscopy (XPS) analysis indicated that enhanced Fe oxides and Cr oxides were generated. Electrochemical corrosion tests, including open circuit potential (OCP), electrochemical impendence spectroscopy (EIS), potentiodynamic polarization (PDP) and potentiostatic polarization (PP) were conducted to study the corrosion behavior of SNC steel in 3. 5 mass% NaCl solution, where an improved corrosion resistance was observed. The resulted improvement resulted from the dominated positive effects (the attached Cr alloying element and enhanced oxide film) against the negative effects (the higher roughness and the improved corrosion activity of surface microstructure).