Method for Mitigating Stray Current Corrosion in Buried Pipelines Using Calcareous Deposits

Stray current corrosion in buried pipelines can cause serious material damage in a short period of time. However, the available methods for mitigating stray current corrosion are still insufficient. In this study, as a countermeasure against stray current corrosion, calcareous depositions were applied to reduce the total amount of current flowing into pipelines and to prevent corrosion. This study examined the reduction of stray current corrosion via the formation of calcareous deposit layers, composed of Ca, Mg, and mixed Ca and Mg, at the current inflow area. To verify the deposited layers, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed. The electrochemical tests revealed that all three types of calcareous deposits were able to effectively act as current barriers, and that they decreased the inflow current at the cathodic site. Among the deposits, the CaCO₃ layer mitigated the stray current most effectively, as it was not affected by Mg(OH)₂, which interferes with the growth of CaCO₃. The calcium-based layer was very thick and dense, and it effectively blocked the inflowing stray current, compared with the other layers.

Research Advances of Soil Corrosion of Grounding Grids

A grounding grid plays the role of discharging current and balancing voltage to ensure the safety of the power system. However, soil corrosion can damage the grounding grid, which then can endanger the safe operation of power system. This paper reviewed recent research advances of soil corrosion of grounding grid. The cause, mechanism, types, and influencing factors of soil corrosion of grounding grids were summarized, and the corresponding detection technology and protective measures were also introduced. The paper pointed out that soil corrosion is a serious threat to the grounding grid system. Moreover, the impact mechanism of AC stray current, new corrosion detection technology, and better protective measures still need in-depth research.

Experimental Study on the Influence of Tool Electrode Material on Electrochemical Micromachining of 304 Stainless Steel

Different cathode materials have different surface chemical components and machining capacities, which may finally result in different machining quality and machining efficiency of workpieces. In this paper, in order to investigate the influence of cathode materials on the electrochemical machining of thin-walled workpiece made of 304 stainless steel, five cylindrical electrodes are used as the target working cathodes of electrochemical machining to conduct experiments and research, including 45# steel, 304 stainless steel, aluminum alloy 6061, brass H62, and tungsten steel YK15. The stray current corrosion, taper, and material removal rate were used as the criteria to evaluate the drilling quality of efficiency of a thin-walled workpiece made of 304 stainless steel. The research results show that from the perspectives of stray current corrosion and taper, aluminum alloy 6061 is an optimal tool cathode, which should be used in the electrochemical machining of thin-walled workpieces made of 304 stainless steel; on the aspect of material removal rate, the 45# steel, 304 stainless steel, and aluminum alloy 6061 present close material removal rates, all of which are higher than that of brass H62 and tungsten steel YK15. Based on comprehensive consideration of both machining quality and machining efficiency, the aluminum alloy 6061 is the best option as the cathode tool in the electrochemical machining of thin-walled workpieces made of 304 stainless steel.