Papers by Keyword: Corrosion Resistance

Abstract: In order to study on mechanical performance as the target of environmental corrosion resistance property, three kinds of glass fiber fabrics like biaxial warp knitted fabric, biaxial stitch-bonded felt and three axial warp knitted fabric were used to prepare textile reinforced composites in five layers laminated structure, which were soaked in seawater environment for 180 days. The result showed that, the surface appearance of textile reinforced composite became muddy and the color became darker, the tensile strength and bending strength of composites decline of the whole with the extension of soak time, the average loss rate of tensile and bending performance are respectively 24.8% and 56.5%, all of these provide the theoretical basis for researching and developing high-quality composite materials.

Abstract: In this paper, Pd ions doped cerium conversion coating (CeCC/Pd) was deposited on AA2219-T87 aluminum alloy by electroplating. The microstructure and composition of the coating were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). Corrosion behavior of AA2219-T87 aluminum alloy with the coating was investigated in 3.5wt.% NaCl solution at the room temperature. XRD and XPS results indicate the existence of cerium-oxide and palladium-oxide in the CeCC/Pd. Polarization curves show that the CeCC/Pd exhibits excellent corrosion resistance. The corrosion current density of the CeCC/Pd decreases by two orders of magnitude compared with the CeCC. The improvement of corrosion resistance would be attributed to the small grain size, good compactness and adhesive strength of the composite coatings.

Abstract: The effect of enhanced solution treatment on microstructures, tensile properties, intergranular corrosion and exfoliation corrosion of a 6013 type aluminum alloy proceeded via various solution treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM), tension testing and corrosion resistance testing. The results show that compared with the conventional solution treatment (560°C×2 h), the enhanced solution treatment (560°C×2 h+570°C×2 h) can improve ultimate tensile strength and elongation, the corrosion resistance become worse after 151°C×8 h+191°C×8 h artificial aging. The tensile strength increase is believed to resulting from the coarse second phases dissolve. The corrosion resistance decrease is due to grain growth.

Abstract: The microstructure and corrosion behaviour of AM50/SiC magnesium matrix composites reinforced with SiC particles were investigated. Composites containing 10 wt. % of SiC were fabricated by means of gravity casting. Technical grade silicon carbide used for the composites fabrication was subjected to a purification procedure leading to the removal of iron containing impurities from its surface. The corrosion resistance of the composite with purified SiC particles was compared to the corrosion resistance of the one containing crude technical grade silicon carbide as well as to the corrosion resistance of the matrix alloy. Voltammetry and an electrochemical noise technique as well as hydrogen evolution rate measurements were utilized for that purpose. Corrosion tests were performed in 0.5 mol dm³ NaCl saturated with Mg (OH)₂. It has been demonstrated that the composite containing purified SiC was less susceptible to corrosion than the one containing crude SiC particles. Both composites were less resistant to corrosion than their matrix itself. Regardless of a purity level of SiC which was used for the composites fabrication, the same constituents were revealed in their microstructure, namely: α-phase (a solid solution of aluminium in magnesium), fully divorced eutectic α + γ (where γ-phase is Al₁₂Mg₁₇), intermetallic compound Al₈Mn₅ and SiC particles uniformly distributed in the whole volume of the matrix.

Abstract: The aim of this work which is a part of larger approach, is the surface functionalization by means of plasma electrolytic oxidation (PEO) as a pretreatment prior to the application of biopolymer. The process was developed for the number of magnesium alloys, and AZ31, RZ5 and ZM21 in particular. An oxide layer was formed in two step consecutive process in KOH-Na₃PO₄ and KOH-NaF solutions. The coatings are built from sub-layers: reach in F at the metal-coating interface containing small pores and top layer with larger pores. An important feature for the surface biocompatibility is a presence and distribution of P within the top part of the coating which create a nucleation sites for the development of calcium phosphates. From the results of long term impedance measurements carried out in simulated body solution (SBF) at 37°C it may be concluded that the best corrosion protection is provided by the anodic layer formed on AZ31 alloy. After the testing the surface of alloys studied in this work was covered by a film of compounds containing calcium and phosphorus.

Abstract: This paper presents the results of investigations on electrolytic polishing and anodic passivation of Ti-15Mo alloy. The influence of chemical composition of the bath used in electrolytic polishing and anodic passivation process on the morphology, wettability and corrosion resistance of the electrochemically modified vanadium-free Ti-15Mo alloy was presented. The electropolishing process was carried out in a solution containing: sulphuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Moreover, the anodic oxidation process was carried out in a 1.0 M H₂SO₄, 1.0 M H₃PO₄ and 0.5 M solution of K₂SiO₃ and 5 g/dm³ KOH. It was found that the electrolytic polishing and anodic passivation led to significant improvement of the surface morphology. The electrolytic polishing and anodic passivation of Ti-15Mo improved corrosion resistance of the alloy in contact with of Ringer's physiological solution. The samples anodised at 100 V in 1.0 M H₃PO₄ presented the highest corrosion resistance.

Abstract: The article compares the corrosion properties of oxide layers formed on titanium nitride (obtained in glow-discharge nitriding) using electrolytic plasma oxidation. The corrosion properties are analysed in correlation with the surface morphology, microstructure and chemical composition of the layers. The oxidation processes were carried out in 10% and 25% phosphoric acid (V) solutions containing Ca²⁺ calcium ions. In each of these environments, oxide layers were formed using three oxidation potentials: 200V, 400V and 600 V. The oxidation potential and the concentration of acid and calcium ions in the oxidation solution was shown to affect the morphology of the surface and the corrosion properties of the oxide layers obtained.

Abstract: The corrosion resistance of oxide layers produced on titanium nitride (obtained in glow-discharge nitriding) by means of electrolytic oxidation at different potentials and durations is presented in the paper. The oxidation processes were carried out in phosphoric acid (V) (25wt.%) containing Ca²⁺ calcium ions. Two plasma oxidation potentials of 40 V and 100 V were applied. Treatment was carried out at two different process durations, i.e. 30 minutes and 120 minutes. The impact of oxidation potential and process time on the morphology of the surface and corrosion properties of the oxide layers obtained was examined.

Abstract: It is known that load-bearing metallic structures that are in service in the atmospheric conditions showed that are exposed to corrosion. The known-in-the art paint-and-lacquer protective coatings can provide protection of metal surfaces for a rather short period between 5 to 10 years. That is why these structures should be protected by the more advanced coatings of new generation, namely: geocement-based coatings which differ from the known-in-the-art binding materials by formation in the hydration products of the zeolite-like minerals and feldspathoids. The paper discusses substantiation of choice of geocement composition in the (хК, уna)₂O⋅Al₂O₃⋅nSiO₂⋅mH₂O system, target synthesis of hydration products of the geocements matrix in the fields of dynamic cavitation, optimal parameters of cavitation treatment aimed at nanostructurization of the geocements matrix in order to synthesize zeolite-like and hydromicaceous phases, choice of appropriate hardening agents and fillers etc. for producing highly efficient protective coatings with high corrosion resistance, high adhesion to metallic substrate and durability.

Abstract: The work presents a structural and corrosion resistance analysis of Mg-based bulk metallic glasses in “as-cast” state. The studies were performed on bulk glassy samples in the form of plates. The structure analysis of the samples in “as-cast” state was carried out by the XRD and DSC methods. The corrosion behavior of the bulk glassy alloys and pure magnesium samples was studied by electrochemical measurements and immersion tests in 5% NaCl solution at room temperature. For the amorphous alloys the highest corrosion potential was achieved, indicating the formation of protective surface layers with Mg and Cu oxides. The corrosion behavior of the alloys with Zn and Ni addition was found to be better than pure magnesium.