Effect of SRB and Applied Potential on Stress Corrosion Behavior of X80 Steel in High-pH Soil Simulated Solution

The effect of SRB and applied potential on the stress corrosion sensitivity of X80 pipeline steel was analyzed in high-pH soil simulated solution under different conditions using a slow strain rate tensile test, electrochemical test, and electronic microanalysis. The experimental results showed that X80 pipeline steel has a certain degree of SCC sensitivity in high-pH simulated solution, and the crack growth mode was trans-granular stress corrosion cracking. In a sterile environment, the SCC mechanism of X80 steel was a mixture mechanism of anode dissolution and hydrogen embrittlement at −850 mV potential, while X80 steel had the lowest SCC sensitivity due to the weak effect of AD and HE; after Sulfate Reducing Bacteria (SRB) were inoculated, the SCC mechanism of X80 steel was an AD–membrane rupture mechanism at −850 mV potential. The synergistic effect of Cl− and SRB formed an oxygen concentration cell and an acidification microenvironment in the pitting corrosion pit, and this promoted the formation of pitting corrosion which induced crack nucleation, thus significantly improving the SCC sensitivity of X80 steel. The strong cathodic polarization promoted the local corrosion caused by SRB metabolism in the presence of bacteria, whereby the SCC sensitivity in the presence of bacteria was higher than that in sterile conditions under strong cathodic potential.

Electrochemical Production of Bismuth in the KCl–PbCl2 Melt

An anode dissolution of binary metallic lead–bismuth alloys with different concentrations of components has been studied in the KCl–PbCl2 molten eutectic. The dissolution of lead is found to be a basic process for the alloys of Pb–Bi (59.3–40.7), Pb–Bi (32.5–67.5), Pb–Bi (7.0–93.0) compositions in the whole interval of studied anode current densities. A limiting diffusion current of lead dissolution was observed at 2 A/cm2 and 0.1 A/cm2 for the alloys of Pb–Bi (5.0–95.0) and Pb–Bi (3.0–97.0) compositions, respectively. The dissolution of bismuth takes place at the anode current densities exceeding the mentioned values. The number of electrons participating in the electrode reactions is detected for each mechanism. Based on the theoretical analysis, the experimental electrolysis of bismuth was performed in the laboratory-scale electrolytic cell with a porous ceramic diaphragm. The final product contained pure bismuth with a lead concentration of 3.5 wt.%.

Technological features of anode dissolution in a combined hardening treatment when developing high-speed rotors

Is studied of the features of anodic dissolution in the process of local combined processing of metal removal points with surface defects arising during balancing of high-speed rotors in connection with the softening of working surfaces from unwanted technological heredity. The ways of improving the processes of their technological refinement using local hardening methods are shown, calculation formulas are given technological parameters of the anode process.

Micro Electrochemical Milling of Micro Metal Parts with Rotating Ultrasonic Electrode

With the rapid development of MEMS, the demand for metal microstructure is increasing. Micro electrochemical milling technology (MECM) is capable of manufacturing micro metallic devices or components based on the principle of electrochemical anode dissolution. To improve the capacity of MECM, this paper presents a compound method named ultrasonic vibration-assisted micro electrochemical milling technology (UA-MECM). Firstly, the simulation and mathematical model of UA-MECM process is established to explain the mechanism of ultrasonic vibration on micro electrochemical milling. Then, the effects of ultrasonic parameters, electrical parameters and feedrate on machining localization and surface quality are discussed considering sets of experiments. The surface roughness was effectively reduced from Ra 0.83 to Ra 0.26 µm with the addition of ultrasonic vibration. It turns out that ultrasonic vibration can obviously improve machining precision, efficiency and quality. Finally, two- and three-dimensional microstructures with good surface quality were successful fabricated. It shows that ultrasonic vibration-assisted electrochemical milling technology has excellent machining performance, which has potential and broad industrial application prospects.

Potentiodynamic Study of the Anodic Behavior of Zn5Al Alloy Doped with Manganese

The widespread use of zinc-aluminum alloys as protective coatings for structures, products, and structures requires studying the effect of various additives in such alloys on their corrosion resistance in various environments. In studying the anode behavior of alloys, potentiodynamic methods are widely used to select methods of protection and increase the stability of anode alloys under given operating conditions. The article presents the results of a potentiodynamic study of the corrosion-electrochemical behavior of Zn5Al alloys doped with manganese in various electrolytes. An increase in the manganese concentration within the studied concentrations leads to a shift in the standard potential and pitting potential to a positive region compared to the initial Zn5Al alloy, which indicates a decrease in the corrosion rate of the studied alloys by 2-2.5 times with respect to the base alloy. An increase in the concentration of chloride ions in the electrolyte leads to a decrease in the electrochemical potentials of corrosion and pitting formation of alloys, which indicates an increase in their anode stability. An increase in the anode stability of the protective coatings of alloys depends on the time spent in an aggressive environment: the longer the time, the lower the rate of anode dissolution.

Wastewater electrooxidation using stainless steel electrodes

Wastewater contains essential nutrients for crops, and after proper treatment its reuse is beneficial to farmers in arid and semi-arid areas. Electrooxidation is an environmentally friendly technology used for treatment of domestic, industrial and agrozootechnical wastewater. During electrooxidation, organic compounds are oxidized at the interface between the anode and the aqueous solution, as a result of the reduction reaction at the cathode. Tests were performed on wastewater collected from the lagoon of a cattle farm, using an electrooxidation cell with stainless steel electrodes. The removal of pH, conductivity, turbidity, color, total N, total P, COD and BOD was investigated at specific voltages of 0.025 V cm-2, 0.05 V cm-2 and 0.1 V cm-2 and various electrolysis times (15, 30, 60 and 120 minutes). Results show that electrooxidation is effective in reducing total N by 24 %, total P by 47 %, BOD by 47 % and COD by 82 %. After completion of tests, the suspended solids were decanted towards the anode area, due to the action of coagulant Fe2+/Fe3+ ions formed by anode dissolution, and the water was clarified. The effluent complies with the standards to be reused to irrigate crops tolerant to salinity grown in permeable soils.

Principles of the express method for controlling interelectrode space condition during wire electrochemical processing

In the practical implementation of the sequential wire electrical discharge machining – pulsed electrochemical machining (WEDM – PECM) technology and in order to perform high quality electrochemical processing, there is a need for the real-time operational control of electrical parameters of inter-electrode space and corresponding adaptive correction of amplitude-frequency power supply parameters (AFPSP). In the context presented by the authors, a mathematical apparatus and an algorithm of operational galvanostatic mode monitoring of anode dissolution using wire electrode-tool are proposed. This will allow adaptive adjustment of AFPSP to ensure controlled passage of electrochemical reactions and significantly increase process stability, dissolved surface layer thickness uniformity along entire electrode tool movement trajectory and resulting surface quality.