Papers by Keyword: Corrosion Resistance

Abstract: The hardness, compressive strength and corrosion rates of LC4 aluminum alloy in 3.5% NaCl solution before and after cryogenic treatment were measured. The microstructure, mechanical properties after cryogenic treatment and corrosion resistance of LC4 aluminum alloy were investigated. The results show that cryogenic treatment can enhance the hardness of annealed LC4 aluminum alloy. An aging treatment at 120 °C for 24 h after cryogenic treatment yielded corrosion-resistant LC4 aluminum alloy with better mechanical properties.

Abstract: Zinc phosphate coating is commonly used for corrosion protection of metallic materials, mainly mild steel. In this study, influence of the pH of phosphating bath on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different pH values (1.75 ~ 2.75). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coating was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that better surface coverage and corrosion resistance for the steel phosphated at pH 2.75.

Abstract: The influence of phosphating temperature on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different temperatures (45 ~ 75 C). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coatings was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that the increase in temperature of the phosphating bath up to 55 C caused an increase in surface coverage and in turn resulted in better corrosion resistance. At high temperature (65 °C and 75 °C) the deposition coverage decreased indicating that the best coverage for the phosphate layer on the metal surface was achieved at 55 °C

Abstract: Aluminum alloy have the active chemical properties,low standard electrode potential, and the surface will be easily forming about 1-3nm oxide film in dry air, therefore aluminum alloy have the poor corrosion resistance.ZrN film deposited by mid frequency reactive magnetron sputtering process on aluminium alloy surface in order to improve the corrosion performance. Study the influences of nitrogen flow rate, sputtering time and temperature to the corrosion performance. The results show that: The corrosion performance of ZrN films will be improved with the nitrogen flow rate increase,but when the nitrogen flow rate was more than 18sccm, ZrN film corrosion resistance will be reduce;The corrosion performance improved with the sputtering time increase,when the time reach 15min, ZrN film corrosion resistance was no longer increase;The corrosion performance improved with the temperature, when the temperature reach 130°C, the corrosion resistance was no longer increase.The best process parameters was: nitrogen flow rate 18sccm, sputtering time 15min, temperature 130°C.

Abstract: Micro-arc oxidation (MAO) coatings were synthesized on MB3 magnesium alloy substrate. Two different electrolyte (Ⅰ) and electrolyte (Ⅱ) were adopted, and the performance of ceramic coatings was compared. The morphology feature, phase composition, and chemical composition of the formed coatings were studied by metallographic microscope, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), XRD, respectively. The corrosion resistance of the coatings was evaluated by salt spray test. The research results show that, the starting and terminal voltage are different during the oxidation process, they are 220V and 375V in the electrolyte (Ⅰ), and 150V and 270 V in electrolyte (Ⅱ). After MAO, The sample surface in electrolyte (Ⅰ) is light gray, and looks tender and smooth. The ceramic coatings obtained in electrolyte (Ⅱ) are relative rough and white in colour. But MAO coatings obtained in electrolyte (Ⅱ) has higher deposition rate. Salt spray test show the corrosion resistance of samples obtained in electrolyte (Ⅱ) are better than those in electrolyte (Ⅰ), which is related to the thickness of the MAO coatings.

Abstract: The zinc-nickel alloy coatings were electrodeposited by changing the concentration of the NiSO₄ • 6H₂O in the plating bath. The scanning electron microscopy (SEM) was used to observe the coating’s surface morphology. The EDS was applied to test the coating’s nickel content. The corrosion resistance was studied by using the Tafel curves, AC impedance spectra and the neutral salt spray test. The results showed that: The coating’s nickel content could reach 12.56% when the NiSO4 • 6H2O concentration was 8g/L in the bath and the coating was very smooth, dense and bright. Its corrosion potential was low and its corrosion reaction resistance was best with red rust time up to 46d, so it had good corrosion resistance. But when the NiSO4 • 6H2O concentration was changed, the coatings’ corrosion resistance would be more or less changed.

Abstract: In order to increase the corrosion resistant and reduce the interfacial contact resistance of the stainless steel, the duplex treatment technology of electroplating Cr and plasma-assisted nitriding process for AISI 304SS is exploited. X-ray diffraction (XRD), scanning electron microscopy (SEM) and the electrochemical tests such as potentiodynamic and potentiostatic polarization in the simulation PEMFC environments are measured. XRD showed that the surface layer of the 540 ° C and 550 ° C were Cr and Cr2N; the 580 °C was the CrN and Cr₂N. The nitride sample of the 550 °C could see the closure process of the mesh crack. Compared with the simulated PEMFC anode environment, higher corrosion resistance was showed in the simulated PEMFC cathode environment. The current density of the 540°C, 550°C and 580°C samples were negative at the operating potential -0.1V, which would provide cathodic protection to the metallic bipolar plates. In the simulated cathode environment, the current densities of the three samples were quickly stabilized, the surface quickly formed a stable passive film.

Abstract: The paper introduces the rotating disk method, its features and the scope of application. It also describes the application of this technique in the research of corrosion of cement-based materials caused by aggressive liquid solutions and the effect of flow of solutions on the corrosion rate

Abstract: The objective of this study was to evaluate the corrosion behavior of Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) with immersion in an acidic saline solution containing fluoride by investigating change in color and the surface structure of the oxide film. With immersion in fluoride-containing solution, TNTZ showed a less marked change in color than commercially pure titanium (TI), and a smaller decrease in glossiness. The outermost surface was covered with oxides from its constituent elements at before and after immersion in solution with or without fluoride. When immersed in fluoride-containing solution, the film consisted of larger niobium and tantalum oxides than that before or after immersion in solution without fluoride. In summary, TNTZ showed superior resistance to discoloration to TI after immersion in fluoride-containing solution. The results suggest that the subsequent increase in niobium and tantalum fractions in the oxide film in TNTZ improves resistance to corrosion.

Abstract: In this paper, the corrosion behaviors of Sm-based bulk metallic glasses (BMGs) were investigated by immersion test. It was found that with Co content increasing the ability of corrosion resistance of the alloy increases for Sm-based bulk metallic glasses. A comparison study was made on the corrosion behaviors between the glassy state alloys and crystalline alloys with the same ingredients. The results show that the glassy state alloy has the better corrosion resistance.