Papers by Keyword: Passive Layer

Abstract: Stainless steel 316L (SS316L) is widely used for applications that require corrosion resistance, especially in acidic environments. Despite its importance, the corrosion mechanism of SS316L in concentrated sulfuric acid at room temperature has not been sufficiently studied. In this research, the corrosion behavior of welded and bent SS316L specimens was investigated by varying the surface roughness, achieved by ground using 120-grit abrasive paper and polished until it mirror-like. The specimens were compared through immersion tests for three days at a temperature of 25°C. The chemical composition was analyzed using optical emission spectroscopy (OES), and the microstructure was observed using optical and scanning electron microscopy (SEM). Experimental tests and analysis showed that surface roughness increased the corrosion rate. Increasing the sulfuric acid concentration also increased the corrosion rate, but at a concentration of 50% wt, no corrosion occurred due to the stability of the passive layer.

Abstract: In the presented work on chronoamperometry, the Cottrell model has been generalized by taking into account a thin porosity layer covering the surface of the electrode and Tafel kinetics of an electrode reaction. The effective diffusion coefficient inside a porosity layer is calculated by Bruggeman’s law. It is shown that in the quasi-stationary approximation of diffusion inside a thin porous layer, the chronoamperometry problem can be solved analytically. The obtained solution has been compared with the results of direct numerical simulations and a good agreement is shown. Limiting cases of the solution related to low and high porosity are considered.

Abstract: The corrosion behavior of galvanized steel in corrosive media of simulated concrete pore solution (SPS) with and without NaCl has been studied for applying it to porcelain insulator’s pins in high-voltage alternating current (HVAC) transmission line. It was found that zinc coating of galvanized steel was corroded increasingly for the first 3 days corrosion test in SPS mixed with NaCl solution. After that the passive layer was formed on the surface of galvanized coating and consequently, the corrosion rate was dramatically decreased nearly five times of initial corrosion rate after 21 days. In this experiment, the investigations have been performed by SEM, optical microscope and visual observation. The results show that this compact and well adherence passive layer can be effectively hindered the corrosion process.

Abstract: In this study, we enhanced the corrosion fatigue life of a TiNi shape-memory alloy wire using a thermal oxidation treatment technique that can generate a passive layer on the wire surface. We followed the following procedure for the thermal oxidation treatment. First, the as-received material with an oxide film was mechanically polished to remove the film using an abrasive paper and a buffing compound. Second, the material was heat-treated in an electrical furnace filled with an N₂-20 vol% O₂ gas for 1 h at 673 K. Subsequently, the material was allowed to cool in the furnace. The results of this treatment are summarized as follows. (1) A passive layer was uniformly generated on the surface of the TiNi shape-memory alloy wire via thermal oxidation on a macroscopic scale; this significantly improved its corrosion resistance. (2) Thermal oxidation extended the corrosion fatigue life of the treated material more compared with HT in air. In addition, we found that the layer generated via the thermal oxidation treatment can maintain adhesion to the base material even when subjected to a bending strain greater than 1%.

Abstract: The paper reports the behavior of TiNbZrTa in biological solution which simulates the body conditions (SBF-simulated body fluids) with different pH values. It has determinate the ion release quantities in time in SBF and the passive layer transformation on the implant surface. The used techniques were ICP-MS, FT-IR and contact angle measurement.

Abstract: Surface analysis techniques (XPS and grazing incidence X-ray diffraction GIXRD) and electrochemical techniques have been combined to elucidate the effect resulting from Cr+ and N+ co-implantation in the formation and evolution of passive layers generated on two different stainless steels (AISI 430 and AISI 304L) in alkaline medium. The results show that the nitrides formed on AISI 430, identified as (Cr,Fe)2N1-x, are less resistant to dissolution while the nitride phase formed in AISI 304L, NCr with nanocrystalline structure, allows the compact growth of the oxide film.

Abstract: After solid-solution and aging treatment, the copper-bearing ferritic stainless steel has been investigated by TEM fitted with X-ray EDS and XPS methods. The TEM and EDS shown that the rod-like precipitation phase was є-Cu, and distributed dispersively throughout in the matrix. The most important result from XPS analysis confirmed that except the topmost of passive film, copper appeared as element state and its concentration kept constant in the inner surface of the material. It was found that the material shown an excellent antibacterial property to staphylococcus and coliform bacteria, after passive film elimination,