Pitting Corrosion Behavior and Surface Microstructure of Copper Strips When Rolled with Oil-in-Water Emulsions

Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. It was found that the corrosion current densities of the rolled Cu strips increased with accumulated reduction, which also lowered the pitting potentials and weakened their corrosion resistances. Therefore, the corrosive tendency of Cu strips under different rolling reductions (ε) followed the order of ε0% < ε20.7% < ε50.6% < ε77.3%. The Cu surface easily reacted with chlorine, sulfur, and carbon components from O/W emulsions to generate pitting corrosion. Under the interactive effect of pitting corrosion and stress corrosion, pits expanded along the rolling direction. The aggregation of anions in surface defects, such as dislocations, metastable pits, and microcracks, further accelerated the pitting corrosion of the surface.

Effect of conditions and parameters of drawing on strength and surface condition of basalt continuous fibers

Basalt continuous fibers are used in the development of new composite materials. The influence of various factors on the strength and formation of the surface microstructure of basalt continuous fibers is considered. An experimental determination of tensile strength was performed and the surface condition of continuous andesite-basalt fibers with a diameter of 8 to 10 μm fibers was investigated. It is established that the strength of fibers, among other factors, is influenced by the conditions of their production, which are determined by the drawing parameters: the production temperature, the level of melt in the feeder and the winding speed. The effect of production temperature on the strength of the fibers was the greatest. It was found that the fibers obtained at a production temperature of 1450 °C had a strength of 24—28% greater than that of the fibers obtained at a production temperature of 1400 °C. The separate influence of other parameters of drawing, the level of melt in the feeder and the winding speed on the strength of the fibers is less significant. A qualitative relationship between the state of the surface of the fibers and the conditions of their production at different parameters of formation. The greatest influence on the change in the state of the surface of the fibers has the temperature of fiber production. It is established that the surface of the fibers obtained at a production temperature of 1450 °C is more homogeneous with a small number of visible defects. On the other hand, on the surface of the fibers, which are obtained at a production temperature of 1400 ºC, there is a large number of defects. There is also an increase in the defect of the surface of the fibers, which are obtained at low levels of melt in the feeder and the winding speed. Keywords: continuous fibre, surface structure, strength, cooling rate, production temperature, winding speed, melt level in the feeder.

Development of a Protective Coating for Evaluating the Sub-surface Microstructure of a Worn Material

In the current study, electrolytic deposition using two different electrodes, copper (Cu) and nickel (Ni) was investigated with the aim of protecting the worn surface during mechanical sectioning and polishing, for a posterior examination of the sub-surface microstructure. The efficacies of the two coatings were visually assessed based on its adhesivity and the ability to protect the wear tracks of an as-cast 26% Cr high chromium cast iron (HCCI) alloy. It was observed that electrodeposition using Cu as the electrode was ineffective owing to a poor adhesivity of the coating on the HCCI surface. The coating had peeled off at several regions across the cross-section during the mechanical sectioning. On the other hand, Ni electroplating using Ni strike as the electrolyte was successfully able to protect the wear track, and the sub-surface characteristics of the wear track could be clearly visualized. A uniform coating thickness of about 8 µm was deposited after 30–40 min with the current density maintained between 1 and 5 A/dm2. The presence of the Ni coating also acted as a protective barrier preventing the ejection of the broken carbide fragments underneath the wear track.

Release of nickel ions and changes in surface microstructure of stainless steel archwire after immersion in tomato and orange juice

Stainless steel archwire is an important component of orthodontic appliances that have the potential to corrode. Consumption of foods and beverages with a low pH, such as fruit-based juices, can trigger the release of nickel ions in stainless steel archwire. This study aimed to determine the difference in the amount of nickel ions release and the surface microstructure of stainless steel archwire after immersed in tomato and orange juice. The sample used is stainless steel archwire with a diameter of 0.016 inches and length of 5 cm immersed in 15 ml of solution and then stored at 37°C in an incubator for 24 hours. The samples were divided into three groups (immersed in tomato juice,orange juice and artificial saliva), each group consisted of 9 samples. The solution was tested using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to determine the number of nickel ions released. The archwire surface microstructure was tested using a Scanning Electron Microscope (SEM). The results showed that the average amount of nickel ion release in orange juice is more than tomato juice. There was a significant difference between the amount of nickel ion released and surface microstructure on stainless steel archwire after being immersed in tomato and orange juice.

Release of nickel ion and surface microstructure of NiTi archwire after immersion in tomato and orange juice

One of wires commonly used in orthodontic treatment is nickel-titanium (NiTi) archwire. NiTi archwire has the potential to release ions that can cause allergic and cytotoxic reactions. This study aimed to specify the difference in the amount of nickel ion release and surface microstructure of NiTi archwires after immersing in tomato and orange juice. NiTi archwire with a diameter of 0.016 inches and a length of 5 cm was used as the sample, which was immersed in 15 ml of solution and then stored at 37°C in an incubator for 24 hours. The samples were divided into two tretment groups (immersed in tomato and orange juice), each with nine samples. The immersion solution was tested for ion release using an Inductively Coupled Plasma–Mass Spectrometer. The microstructure of the wire surface was examined using a scanning electron microscope (SEM). The results revealed that group 1 has higher average amount of nickel ion release than group 2 and control. SEM result showed that the surface microstructure of the NiTi archwire in group 1 is roughest. There was a significant difference between the amount of nickel ion released and surface microstructure on NiTi archwire after being immersed in tomato and orange juice.