Papers by Keyword: Corrosion Behaviour

Abstract: The connecting of contrasting metals, namely double stainless steel to steel made of carbon, has taken place. performed using a hybrid welding system. A TIG and MIG welding joining based hybrid joining method was designed. The microstructures of the dissimilar metal joints were studied and the grains are coarser as contrast to the use of a single the welding process process by itself. With the addition of TIG welding to the process of MIG welding, the water-holding capacity of the metal in molten state pool is significantly improved. The nominal corrosion behaviour of the weldments was found better than the single arc welding system alone. The passivation behaviour of the joints was in the similar line to that of double stainless steel base metal. The pitting resistance of the joints in 1 M NaCl solution was inferior to the base metals.

Abstract: Tin slag is one of smelting waste that has not been utilized yet. As substitutional, cementious material in concrete replaced the function due to its similar oxide existence with Ordinary Portland Cement (OPC) such as SiO₂, CaO, Al₂O₃, and Fe₂O₃. The objective of this research is to evaluate the corrosion behavior on the surface of carbon steel rebar due to the effect of partial substitution of tin slag in mortar. In this research, final tin slag added with ratio of 0.1, 0.2, 0.3 from total cement. The concrete had been cured for 28 days of immersed in NaCl 3.5% solution for 6 days. The corrosion behavior against steel reinforcement inside concrete measured by Electrochemical Impedance Spectroscopy (EIS) method and the result shows that 20% tin slag from the total of cement give the most competitive corrosion resistance than the others.

Abstract: Biodegradable Mg alloys are a new class of temporary implant materials for musculo-skeletal surgery. Recent studies show that Mg-based alloys can be biocompatible and there is a high demand to design Mg alloys with adjustable corrosion rates and suitable mechanical properties. An approach to solving this challenge might be the use of Mg metal matrix composites (Mg-MMC). In this study, a Mg-MMC composed of ZK60 was investigated as the base material and hydroxyapatite (HA) particles were added for tailoring its properties. The composite was produced by high-energy ball milling followed by hot extrusion. This processing route was chosen, as HA in contact with molten Mg releases a toxic gas (phosphine – PH₃). The HA particles were homogeneously distributed in the ZK60 matrix after ball milling and the composite was consolidated by hot extrusion. This work presents the influence of different amounts of HA on corrosion behavior and mechanical properties of the composite. Corrosion properties were evaluated by immersion and electrochemical measurements in physiological media at 37 °C. A slight improvement in the corrosion resistance was observed for Mg-MMC due to the presence of more stable corrosion products. Compression tests were used to measure the mechanical properties. Under compression, samples showed a slight increase in the compressive yield strength with the addition of HA, while the ultimate strength did not change significantly.

Abstract: Corrosion behaviour of AZ91DSm1.0 with different preparation methods(vacuum melting and common melting) is investigated. X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), corrosion weightless experiment and the potentiodynamic polarization curve are applied to characterize the corrosion behaviour. Results show that vacuum melting alloy possess higher corrosion resistance than common melting alloy. This is attributed to the rod-shaped Al3Sm which was formed in common melting alloy will have certain fragmentation effect on matrix that can lead to defects.

Abstract: Recently, Composite Sandwich Panel (CSP) technology considerably influenced the design and fabrication of high performance structures. Although using CSP increases the reliability of structure, the important concern is to understand the complex deformation and damage evolution process. This study is focused on the flexural and indentation behavior of CSP made of chopped strand mat glass fiber and polyester matrix as face sheets and polyurethane foam as foam core subject to flexural and indentation loading condition. A setup of three-point bending and indentation test is prepared using different strain rates of 1mm/min, 10mm/min, 100mm/min and 500mm/min to determine the effects of strain rate on flexural and indentation behavior of CSP material. The load-extension, stress-extension response and energy absorption of the panel show the relation between the flexural and indentation behavior of panels to strain rate as by increasing the strain rate, the flexural properties and the energy absorption of panel are increased.

Abstract: The corrosion behavior of anodized powder metallurgy Al/2wt%Mg composites reinforced with the short fibre alumina Saffil^TM was studied using potentiodynamic polarization in 3.5% NaCl solutions. The materials under investigation were fabricated using powder metallurgy route. Anodising process has been done to the materials to improve their corrosion resistance. Anodising process were carried out in sulphuric acid solutions with different anodizing voltage, which are 10V, 12V, 14V, 16V and 18V and different concentration of sulphuric acid (5%, 10%, 15%, 20% and 25%). Results from Tafel plot showed that corrosion behavior of PM Al-Mg composites strongly depends on the anodizing parameters. Corrosion resistance increases with the increase in anodizing voltage and concentration of sulphuric acid. The maximum corrosion resistance was recorded by the PM Al-Mg composite anodized using 16V and in the 15% concentration of sulphuric acid.

Abstract: Microstructure, mechanical and corrosion properties of Mg-10Gd-2Zn and Mg-10Gd-6Zn (all in wt.%) were evaluated in the as-cast condition. The microstructures of both alloys contained (Mg, Zn)₃Gd phase at the interdendritic regions and long period stacking ordered (LPSO) phase distributed in the matrix. The Mg-10Gd-6Zn alloy consisted of a high volume fraction of (Mg,Zn)₃Gd intermetallic phases continuously distributed along the grain boundaries. The tensile properties, especially the elongation to failure of the Mg-10Gd-6Zn alloy were slightly lower than those of Mg-10Gd-2Zn. An enhancement in creep resistance was observed with Mg-10Gd-2Zn alloy with the post creep tested microstructure showing dynamic precipitation. Corrosion studies indicated that increased Zn content, from 2 to 6 % in Mg-10Gd alloys, significantly reduced the corrosion resistance.

Abstract: Mg-7Y-0.6Zr-xZn (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, wt.%) alloys were prepared by the metal mould casting method. Effect of Zn content on the microstructures and corrosion behaviour were investigated. Results showed that microstructures were refined and volume fraction of secondary phase Mg₂₄(YZn)₅ was increased with increasing addition of Zn element. Results of electrochemical tests demonstrated that the corrosion potential of Mg-7Y-0.6Zr alloy was about -1.77 V, and, with addition of 0.5~2.0 wt.% Zn element, corrosion potential moved to more positive values than that of Mg-7Y-0.6Zr alloy. Mg-7Y-0.6Zr-0.5Zn alloy possessed the most positive corrosion potential of -1.53 V. The results of immersion test with different time also indicated that corrosion rate could be decreased by addition of 0.5~2.0 wt.% Zn, and Mg-7Y-0.6Zr-0.5Zn alloy exhibited the lowest corrosion rate.

Abstract: This paper presents corrosion behaviour of welded low carbon steel at different welding parameters. Welding process was conducted using metal inert gas (MIG) technique at welding voltage range of 19 to 22 V with 1 V interval, and wire feed rate range of 90 to 120 inch per minute (ipm) with 10 ipm interval. Filler material used was ER 70S-6 with 1.2 mm diameter. Corrosion behaviour of welded carbon steel was tested using synthetic seawater environment with 3.5 wt% NaCl. Microstructure changes and penetration level of weldments were observed using scanning electron microscope (SEM). Results showed that, corrosion rate decreased when the welding voltage and wire feed rate increased with full penetration level of weldment attainment. The lowest corrosion rate occurred at the highest welding voltage and wire feed rate when full penetration of weldment occurred. From metallographic study, iron oxides and pitting was found on the surface of the exposed area after the corrosion test.

Abstract: Micro-arc oxidation (MAO) coatings were prepared on Ti6Al4V alloys surface by using self-made micro-arc oxidation equipment. Its characterizations were systematically detected by Vickers hardness tester, scanning electron microscope (SEM), X-ray diffractometer (XRD) and X-ray fluorescence spectrometer (XFS). Corrosion behaviour of MAO coating and Ti6Al4V alloy in Hank's simulated body fluid were studied comparatively using electrochemical workstations and salt spray test chamber. The experimental results indicated that the MAO coating, with rough surface, high hardness and typical porous ceramic structure, is mainly consist of anatase and rutile TiO₂ phase. Micro-arc oxidation treatment can significantly improve corrosion resistance of Ti6Al4 alloy, and the corrosion resistance of the coating is observably affected by the coating technology. During the micro-arc oxidation treatment, the thickness of the coating increases with the increase of oxidation time, which induce that the corrosion potential and polarization resistance of the coating increase, and the corrosion current reduce. Simultaneously, the thicker the coating, the higher the pitting resistance is. On the other hand, under the same oxidation time, as the current density increases during micro-arc oxidation treatment, the corrosion potential of the coating positive shifts, and the corrosion current reduces.