Papers by Keyword: Passive Film

Abstract: The aim of this study, the corrosion behavior of TiNiCu in artificial saliva (pH5.35) at 37°C was assessed by the use of electrochemical methods. Ti₅₀Ni₄₃Cu₇ (at%) used in this study were made from ingots prepared by the vacuum arc melting (VAM) method. The furnace was purged with argon gas during melting. All melted ingots were then homogenized at 800°C for 3.6 ks. Open circuit potential (OCP) was monitored at 3.6 ks followed by potentiodynamic techniques. The results showed that all chemical composition of orthodontic wires by EPMA were Ti, Ni, Cu, Cr, Fe and Mn. Surface roughness was measured in order to ensure that TiNiCu and SS was significant difference which might affect corrosion resistance. It was seen that TiNiCu orthodontic wires, presented a good corrosion resistance, compared to the stainless steel, probably due to the formation of a protective oxide film mainly constituted by titanium oxide.

Abstract: By means of Ultrasonic shot peening (USSP), a strengthening surface layer was formed on Ti-6Al-4V. The polarization curves with different treatment times were investigated in 3.5% NaCl. The type of semiconductor for passivation film of 30 min treatment was measured by Mott-Schottky curve, and the thickness of the passivation film was calculated.The result of the polarization curves show that the corrosion resistance of the USSP treatment samples is increased by comparing with the untreated sample. Mott-Schottky curve of 30 min USSP treatment sample show that the passive film belongs to n-type semiconductor. The thickness of the passive film is much thicker than the untreated sample. The charge carrier density is smaller than that of untreated sample. These indicate that the surface strengthening improves the corrosion resistance of the Ti-6Al-4V in 3.5% NaCl by forming stable passive film.

Abstract: A study was conducted on the corrosion behavior and characteristics of the passive oxide film of Fe-Mn-Si-Cr-Ni-(Co) shape memory stainless steels (SMSS) in a concentrated nitric acid (HNO₃) solution, based on potentiodynamic polarization, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. The results indicated that Fe-Mn-Si-Cr-Ni-(Co) SMSSs exhibit a passive behavior similar to that of 304L austenitic stainless steel (304L SS). However, unlike 304L SS, their high silicon (Si) content renders them insensitive to intergranular attack in highly oxidizing environments. The XPS analysis also indicated that Si appears to be the main element responsible for the high protectiveness afforded by the passive film formed on Fe–Mn–Si–Cr–Ni–Co SMSS.

Abstract: To resolve the materials corrosion problems during exploiting high H₂S/CO₂ oil and gas field, the corrosion behavior of 718 nickel base alloy for 720 hours was studied, the conditions of the experiment is about temperature=177°C, P(H₂S)=3.0MPa, P(CO₂)=13.5MPa, solution mixed NaCl 20%wt.. The Electronic Parts Manufacturers Association (EPMA) and electrochemical methods was applied to characterize the microstructure, chemical composition and impedance characteristics of corrosion film. The results show that the surface of corrosion film is mainly composition by sulphide of Ni, Cr and Fe, the inside of corrosion film is mainly composition by oxide of Ni, Cr and Fe, electrochemical analysis found the alloy could resist corrosion in this environment.