Papers by Keyword: Corrosion Property

Abstract: In order to alleviate the shortage of global nickel resources, it is imperative to develop low nickel stainless steel. This paper presents a novel approach based on increasing nitrogen and reducing nickel for smelting economical stainless steel. Taking 06Cr19Ni10 stainless steel as the object, the test steels with different nitrogen and nickel content were smelted using vacuum induction furnace (ZG-0.01) under the laboratory conditions, and the effects of alloy content on microstructures, mechanical properties and corrosion properties of the economical stainless steel were investigated. The results show that the microstructure of the tested steel which nitrogen content 0~0.28% and nickel content 5.98~9.63% is still the single austenitic, and the grain size decreases as the nitrogen content increases. Nitrogen deteriorates the impact toughness of the tested steel, and the room temperature impact absorption energy is reduced from 267 J at the nitrogen content of 0 to 228 J at nitrogen content of 0.28%. Rockwell hardness, tensile strength and yield strength increase with the increase of nitrogen content. When the nitrogen content is 0.28%, the optimum mechanical properties of 06Cr19Ni10 steel are obtained. The Rockwell hardness is 95.4 HRB, the tensile strength is 814 MPa, the yield strength is 437 MPa, and the elongation after fracture is 52.5%. The degree of intergranular corrosion of the tested steel is reduced significantly with the increase of nitrogen content, from 0.023 μm to 0.008 μm. The experimental data prove that the composition design concept of increasing nitrogen and reducing nickel is feasible for smelting economical stainless steel.

Abstract: Plastic deformation can induce surface modification, such as shot peening (SP) on workpiece surface is the hot issue of recent scientific research. SP is the efficient way to improve mechanical behavior of specimens by inducing sever plastic deformation on their surface. Nevertheless, this surface treatment induced complex microstructural evolutions such as grain refinement, will enhance the corrosion resistance of specimens. In this work, the microstructure and properties of 34CrMo4 alloy of before and after SP for 20 min have been investigated. The evolution of microstructure and properties were analyzed from the surface and cross-section. The microstructure morphology at the different depth was determined by optical microscope. The results show grain size is increasing with the depth, and the microhardness and compressive residual stress decrease gradually. In terms of corrosion resistance, the 50 μm depth specimen has the best property than other depth, which the potential and corrosion current density are-0.484 V and-5.72 Acm^-2, respectively. The maximum polarization resistance is 2055 Ωcm² by capacitive arc radius of electrochemical impedance spectroscopy.

Abstract: Casting Mg-Zn alloy was corroded on the surface and analyzed the corrosion morphology and corrosion properties under different corrosion conditions. The results show that Mg-Zn alloy is unevenly by corrosion in simulated body fluids and the corrosion products are brittle and easy to break. With the increase of Zn content in Mg-Zn alloy, the corrosion rate of casting Mg-Zn alloy in simulated body fluid is improved obviously.

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: Magnesium and its alloys are potential materials in biodegradable hard tissue implants. However, the fast degradation rates in a physiological environment constitute the main limitation for biomedical application. In this work, the NH₄H₂PO₄- KMnO₄ chemical conversion treatment on the surface was used. The morphology and structure of the coating was observed and analyzed by SEM. The electrochemical behavior in Hanks' simulated body fluid of the coated magnesium was systematically investigated. Our results disclose that the corrosion resistance of the P-coated magnesium is significantly improved.

Abstract: Corrosion behaviors of ultra high strength steel 22MnB5 and its weld were studied based on electrochemical method in the present work. Electrochemical measurements such as Tafel polarization curve and electrochemical impedance spectroscopy were performed to investigate the corrosion mechanisms of 22MnB5 steel and its weld. The testing results indicated the weld metal possessed less corrosion resistance than the base metal, and the main reason for this phenomenon is the microstructure variation of the weld metal.

Abstract: The electroplated Ni-Co-Cr coatings were prepared on surface of a low carbon steel. The microstructure of the deposits were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD), the corrosion resistance of the deposits was evaluated using neutral salt-spray test and polarization measurement. The results show that the deposits are a Co and Cr solid solution in Ni with a grain size of 6.9~10.6nm, were nearly free of corrosion after neutral salt-spray tested 100 hours. With chromium content increasing, the coatings exhibited higher corrosion potential and lower corrosion current, which revealed excellent corrosion resistance.

Abstract: Corrosion resistance of gas-tungsten arc welds in two 21% chromium ferritic stainless steels was benchmarked against ferritic type 441 and austenitic type 304L stainless steels. Salt spray, pitting corrosion and ferric chloride tests were carried out for autogenous welds. Also, electron microscopy and glow discharge optical emission spectroscopy examinations were made.The corrosion resistance in 21% chromium ferritic steel welds in chloride environments was seen comparable to those in type 304L, and an improvement was observed when compared to type 441 steel. However, the Mn-Cr-Ti-S sulfide domain may have an undesirable influence on end-grain pitting in ferric chloride test. Weld oxidation results in poor corrosion protection, and artificial mechanical cleaning alone is inadequate for restoring this, and hence pickling is advised.

Abstract: Magnesium and its alloys have been received huge attention as new kind of degradable biomaterials. However its application hindered by poor carrion resistance fluoride conversion coating was performed due to improve the corrosion resistance of Mg-Ca-Zn alloy. In the present work ccorrosion of behaviour and degradation bahaviour of fluoride treated Mg-Ca-Zn alloy were investigated. Microstructural evolutions were characterized by scanning electron microscopy and energy dispersive x-ray spectroscopy. The corrosion resistance was examined in vitro by potentiodynamic polarization and immersion test in Kokubo solution at room temperature. The coating characterization indicated that the dense and uniform film with 6 μm thickness consists of MgO and MgF₂ formed on the alloy. Polarization tests recorded a significant reduction in the corrosion current density from 188 μAcm^-2 in bare Mg-Ca-Zn to 6.11 μAcm^-2 in fluoride treated alloy as a result of formation MgF₂ protective layer. The in vitro degradation tests showed that the average weight loss of the untreated specimens significantly higher than that of fluoride treated Mg-Ca-Zn alloy. The results revealed that the fluoride conversion coating noticeably improve the corrosion resistance of Mg-Ca-Zn alloy resistance of Mg in Kokubo solution.

Abstract: This paper studies jet fuel’s silver strip corrosion property and analytic technology with different sulfide compounds, and gives the experimental results of the corrosiveness of sulfide, analytic test of total sulfur and elemental sulfur. And then, the chemical compounds, which lead to jet fuel’s silver strip corrosion, are also researched by the experiments of the acid, the alkali, the water, mercury scrubbing and silver nitrate, and through the analyses of the content of halogen, nitrogen compound, the constitute of corrosion products and XPS spectrum. Therefore, the referencing of these research works is helpful to analyze the existence state of sulfide in jet fuel and provide a theoretic foundation to clarify the reason of jet fuel deterioration and silver strip corrosion.