Auxiliary Anode Research Articles

Cathodic Protection Potential Distribution and Anode Ground Bed Optimization Scheme for Low-pressure City Gas Pipe

ABSTRACT The low-pressure gas pipes in some old residence communities of China are often electrically connected to each other and groundings, which brings about great challenges to the design of cathodic protection (CP) system due to large CP current consumption and attenuation effects. The field tests on potential distribution of three types of anode ground beds were conducted, including deep well auxiliary anode ground bed, shallow auxiliary anode ground bed far from gas pipes, and shallow auxiliary anode ground bed close to gas pipes. The results showed that, the shallow auxiliary anode ground bed close to gas pipe provided more protection with less current than other two types of ground bed. Numerical simulations on CP potential distribution of different anode ground beds were conducted and the boundary conditions were determined by inversion calculation based on field tests. Based on the field test and numerical simulation results, the anode ground bed suitable for CP of low-pressure gas pipes electrically connected to groundings is the shallow auxiliary anode ground bed close to gas pipes and the optimized distribution scheme for shallow anode ground beds were proposed.

2-D shape optimization of auxiliary anode for ICCP

In this paper, to determine the influence of the shape of the auxiliary anode on the protection potential distribution in an impressed current cathodic protection (ICCP) system, an electrochemical and a level-set optimization method were combined to optimize the shape of the auxiliary anode. To accomplish this, the square of the deviation between the potential of the structure and the protection potential was used as the objective function, and the level set theory was employed to develop the anode shape. Following a set number of iterations, the optimized anode shape was obtained. Using the optimized anode, a current was injected into the anode surface, and the potential distribution was calculated. The experimental results showed that the potential distribution of the protected surface was uniform, and it could fully protect the protected structure's surface, which helped to avoid overprotection or underprotection.

Performance evaluation of conductive materials in conductive mortar based on machine learning

Conductive mortar auxiliary anode (CMAA) is one of the main materials to realize stable operation of cathodic protection system. However, the conductive material in CMAA is complex and diverse, and its basic physical properties have a complex functional relation with the type and content of conductive material. At present, there is no uniform evaluation criterion, which can realize the evaluation of the action properties of different conductive substances. To address this issue, machine learning was proposed to establish predictive models between input and output factors. The SHAP-value was used to analyze the model's global and local features, and the partial dependency of prediction results. The results show that: on the basis of 241*3 groups of databases, the predictive performance analysis of RFR, GB, XGBoost and LGBM models shows that LGBM is the optimal model, and the determination coefficients of its training set and test set are 0.98 and 0.97, respectively. The LGBM model, combined with SHAP-Value analysis and PDP analysis, reveals the importance ranking of the input features that affect the compressive strength, and can also provide a quantitative evaluation of the effect of the input factors against the compressive strength, providing a new analysis method for material design and performance optimization.

Electrical conductive mortar based on expanded graphite for auxiliary anode

The use of cement-based conductive mortar is an effective way to enhance the long-term operation of impressed current cathodic protection (ICCP) system. However, its widespread use is limited by the challenges of dispersing nano-fillers and the associated cost. To overcome these challenges, this study proposes the use of expanded graphite (EG) as a conductive material due to its strong conductivity, easy dispersion, and low cost. Additionally, multilayer EG flakes can promote cement hydration due to their high specific surface area, thereby improving the mechanical properties of mortar. This study examines the effects of EG content on the mechanical properties and electrical conductivity of the conductive mortar. Results reveal an exponential relation between EG content and mechanical strength, with 1.5% EG content producing the maximum mechanical properties. The resistivity of EG cement mortar decreases as the EG content increases, reaching its minimum at the percolation threshold. At this threshold, the resistivity of conductive mortar is 46.4% of the optimal content for mechanical properties (EG content is 1.5%). The incorporation of EG in cement-based conductive mortar is a viable alternative to traditional materials that can improve both conductivity and mechanical properties. This approach has great potential for enhancing the performance of ICCP systems.

Anticorrosion Method Combining Impressed Current Cathodic Protection and Coatings in Marine Atmospheric Environment

In this study, a new anticorrosion method combining impressed current cathodic protection (ICCP) with coatings that can be applied to marine atmospheric environments is proposed. As the corrosion medium fills the cracks and pores of the coating, an electrolyte film layer is inevitably formed on the metal surface. Therefore, a graphene conductive coating with excellent chemical inertness and shielding performance is selected as the intermediate coating to form an electrolytic cell system with a metal substrate serving as the cathode and a graphene coating serving as the auxiliary anode. By studying the surface corrosion morphologies and electrochemical signals of the coating samples at different protection potentials and coating thicknesses, the optimal potential is determined to be 0.6 V, and the optimal coating thickness is determined to be 20 μm. The samples protected by the joint method have lower corrosion rates and better anticorrosion performance than those protected by the coatings alone.

Cathodic protection of reinforced concrete facilitated by using CNT-CF/cement-based auxiliary anode

In this article, the carbon nanotube-carbon fiber (CNT-CF)/cement-based composite served as a novel auxiliary anode in the form of overlay for the cathodic protection of reinforced concrete (RC) was proposed. The effect of CNT content and age on the conductivity of CNT-CF/cement-based composite was firstly analyzed. After applying the CNT-CF/cement-based composite, the effectiveness of cathodic protection on the reinforcement was evaluated by the corrosion potential and corrosion current, respectively, as measured by Tafel polarization and half-cell potential methods. For comparison, finite element simulation was adopted to calculate the corrosion potential and corrosion current. It showed that the resistivity of CNT-CF/cement-based composite monotonously decreased with increasing content of CNT up to 2 wt.%. When the CNT content was 0.5 wt.%, the resistivity of the composite reached the minimum value of 22.3 Ω·cm. The resistivity for all the groups decreased with increasing age in the first 7 days. Both the experimental and simulated results showed that the CNT-CF/cement-based auxiliary anode improves the cathodic protection effectiveness for RC.

3D Carbon Fiber Skeleton Film Modified with Gradient Cu Nanoparticles as Auxiliary Anode Regulates Dendrite-Free, Bottom-Up Zinc Deposition.

Achieving stable Zn plating/stripping under high current density and large area capacity remains a major challenge for metal Zn anodes. To address this issue, common filter paper is utilized to construct 3D carbon fiber skeleton film modified with gradient Cu nanoparticles (CFF@Cu). The original zincophobic hydrophilic CFF is transformed into gradient zincophilic and reversed gradient hydrophilic composite, due to the gradient distribution of Cu nanoparticles. When CFF@Cu is placed above Zn foil as an auxiliary anode, Zn foil anode exhibits stable, reversible, and dendrite-free Zn plating/stripping for 1200h at 10mA cm-2 and 2 mAh cm-2, 2000h at 2mA cm-2 and 2 mAh cm-2, 340h at 10mA cm-2 and 10 mAh cm-2. Additionally, nucleation barrier of Zn, Zn2+ transport and deposition kinetics are improved. The deposits on the Zn foil anode become homogeneous, dense, and fine. Side reactions and by-products are effectively inhibited. The excellent performance is mainly attributed to the gradient zincophilic field in 3D CFF. A portion of Zn2+ is captured by Cu and deposited within CFF@Cu from bottom to top, which reduces and homogenizes Zn2+ flux on Zn foil, as well as weakens and homogenizes electric field on Zn foil.

Actively controlled anode auxiliary gate super-junction insulated gate bipolar transistor with extremely low

When dealing with the super-junction insulated gate bipolar transistor (SJ-IGBT), due to its unipolar/bipolar mixed conduction mechanism, the approaches to improve its – are not exactly the same as for non-SJ IGBTs. In the pursuit of extremely low , a planar auxiliary anode gate SJ-IGBT (AAG-SJ-IGBT) is proposed based on a 650 V SJ-IGBT to realize a unipolar turn-off as observed in SJ-MOSFETs accompanied by fast switching and extremely low . The planar auxiliary anode gate provides similar effects but better feasibility than conventional trench ones. Sentaurus TCAD simulation results for the proposed AAG-SJ-IGBT indicate a 69% smaller and a 54% lower than the FP-SJ-IGBT, and its – is significantly optimized from cathode-improved SJ-IGBTs. The analysis of carrier and current density reveals the static and dynamic characteristics of the AAG-SJ-IGBT and the principle for excellent – trade-off.

Increased styrene vapor removal and power production by adding silicone oil to microbial fuel cell-based trickling filter

This study increases the mass transfer of hydrophobic contaminants in a microbial fuel cell-based trickling filter (MFC/TF) by adding non-aqueous phase liquid. The removal efficiency, mineralization efficiency and elimination capacity of styrene are respectively increased by 1.56 times, 1.86 times and 1.52 times, the power density is increased by 2.6 times and the internal resistance is reduced by approximately 22% after adding 10% silicone oil to the MFC/TF. This is mainly attributed to a decrease in the internal resistance after adding silicone oil, which increases electron transfer on the surface of the auxiliary anode packing and increases the number of electricity-producing bacteria. Adding 10% silicone oil to the MFC/TF increases the number of degrading bacteria and electricity-generating bacteria in the MFC/TF by 2.3–2.5 times. The performance of the MFC/TF using 10% silicone oil is significantly increased because there is increased mass transfer of styrene in the MFC/TF and increased power generation.

A Shunt-Assisted Silicon Electrode for Micro Electrochemical Machining

Abstract Stray current causes undesired material dissolution in micro-electrochemical machining (micro-ECM). The reduction of stray corrosion, caused by stray current, continues to be a major challenge for accuracy improvement. To limit the distribution of stray current, a shunt-assisted silicon electrode, with an auxiliary anode sharing stray current, is proposed in this study. The auxiliary anode is arranged outside the insulating layer of the sidewall-insulated electrode. It is proved in simulation that the auxiliary anode can help reduce the average material removal rate on the machined surface by 55% and improve processing accuracy. A fabrication process of shunt-assisted silicon electrode by bulk silicon process and thin film deposition process are presented. Microgrooves and holes are machined in ECM experiments. The angle between each side-wall and the vertical plane is less than 10 deg. The gap between the sidewall of the machined structures and electrode-outer-contour is about 30 μm±6 μm for the grooves and 45 μm±10 μm for the holes. These long-term experiments and consistent processing results show the shunt-assisted electrode is reliable in ECM process. But due to the stray corrosion induced by DC power supply and conservative feed method, the effect of the shunt-assisted silicon electrode in inhibiting stray corrosion is not significant. In the future, a micro-ECM system with novel power supply and active control methodologies is expected to better utilize the effect of the shunt-assisted silicon electrode.

Improvement of plasma uniformity and mechanical properties of Cr films deposited on the inner surface of a tube by an auxiliary anode near the tube tail

In order to improve the length of plasma in a whole tube and mechanical properties of Cr films deposited on the inner surface of the tube, a high-power impulse magnetron sputtering coating method with a planar cathode target and auxiliary anode was proposed. The auxiliary anode was placed near the tube tail to attract plasma into the inner part of the tube. Cr films were deposited on the inner wall of a 20# carbon steel tube with a diameter of 40 mm and length of 120 mm. The influence of auxiliary anode voltage on the discharge characteristics of the Cr target, and the structure and mechanical properties of Cr films deposited on the inner surface of the tube were explored. With higher auxiliary anode voltage, an increase in substrate current was observed, especially in the tube tail. The thickness uniformity, compactness, hardness and H/E ratios of the Cr films deposited on the inner surface of the tube increased with the increase in auxiliary anode voltage. The Cr films deposited with auxiliary anode voltage of 60 V exhibited the highest hardness of 9.6 GPa and the lowest friction coefficient of 0.68.

Підвищення ефективності запалювання вакуумно-дугового розряду в джерелах плазми

The analysis of the existing vacuum-arc discharge ignition systems showed the following ways to improve their efficiency: development of new design solutions for both individual units and the entire ignition system as a whole; the use of composite materials to fill the discharge gaps of starting devices; creation of new circuit solutions for power supplies of starting discharges; the use of non-traditional methods of ignition of a vacuum-arc discharge - the transition of a glow discharge into an arc one; using laser radiation to ignite the arc. Criteria for evaluating the reliability and durability of vacuum-arc discharge initiation systems in technological plasma sources are proposed, based on which complex studies of contact-type arc excitation systems with spark surface breakdown and two-stage launch systems with an autonomous plasma injector. Based on the performed studies, designs of vacuum-arc plasma sources with contact-type systems have been developed that ensure their performance in a certain range of technological parameters; The design of the ignition system turned out to be the most effective, in which the ignition electrode and the auxiliary anode are made as a single structural element in the form of a cut cone-shaped spiral. These design features, firstly, do not prevent the condensation on the surface of the starting discharge gap of a part of the metal evaporated by the cathode spot (CS) of the arc during the operation of the device, and secondly, they greatly facilitate the output of the CS from the place of initiation to the working end of the cathode. Here, the magnetic field, under the action of the CS moves, created by the current of the starting discharge itself, flows along with the turns of the cone-shaped spiral. This ignition system does not require a separate power supply and can operate in an automatic mode from the arc power source. To implement a non-contact method of arc excitation using a plasma injector, various designs of it were studied, when the discharge gap was filled with different materials; it was found that the resource of starting injectors when filling the discharge gap with M-7 ceramics does not exceed 104 operations, with 22XC ceramics at the level of 105 operations, and when using a composite material (CM), it exceeds 106 operations at ignition energy of 5 J, an operating pulse frequency of 1 Hz and arc duration 2 s. The developed composite materials are distinguished by increasing resistance to electric discharges and low surface breakdown voltage (up to 100…200 V/mm). Such characteristics are provided by the features of the CM structure, which is a dielectric glassy matrix filled with finely dispersed conductive particles and semiconductor components. The theoretical and experimental dependence of the arc ignition probability on the ignition energy during the operation of the injector in the electric film explosion mode are compared, showing satisfactory agreement between the results.

Current Density Limit of DC Grounding Facilities Considering Impact on Zebrafish (Brachydanio rerio)

Grounding facilities, including high-voltage DC grounding electrodes and auxiliary anodes in impressed current cathodic protection systems, inject current into the ground. This study developed an experimental platform to determine the safe limit of current density for such facilities through an analysis of fish behavior on the platform. Zebrafish (Brachydanio rerio) were selected for the experiment and placed in a tank; two rod electrodes were used to inject direct current into the water. A wireless camera was focused on the water tank to video record possible changes in fish behavior. The output voltage of the DC power source was varied, and the trajectories of the fish under various direct current fields were recorded. A tracking program was developed to analyze the trajectories and quantify the behavior of the fish. A new method combining the trajectories of fish samples with the results of current density calculations for analysis was proposed. Results demonstrated that the zebrafish could sense current in the water and turn when exposed to certain current densities. The intensity of the current at the turning points was statistically analyzed, and the threshold of current density at which the fish could no longer tolerate the current and turned was 0.4231 A/m2.

Ion energy distribution and non-linear ion dynamics in BP-HiPIMS and ACBP-HiPIMS discharge

Investigating the ion dynamics in the emerging bipolar pulse high power impulse magnetron sputtering (BP-HiPIMS) discharge is necessary and important for broadening its industrial applications. Recently, an optimized plasma source operating the BP-HiPIMS with an auxiliary anode and a solenoidal coil is proposed to enhance the plasma flux and energy, named as ACBP-HiPIMS (‘A’-anode, ‘C’-coil). In the present work, the temporal evolutions of the ion velocity distribution functions (IVDF) in BP-HiPIMS and ACBP-HiPIMS discharges are measured using a retarding field energy analyser (RFEA). For the BP-HiPIMS discharge, operated at various positive pulse voltages U +, the temporal evolutions of IVDFs illustrate that there are two high-energy peaks, E 1 and E 2, which are both lower than the applied U +. The ratio of the mean ion energy E i,mean to the applied U + is around 0.55–0.6 at various U +. In ACBP-HiPIMS discharge, the IVDF evolution shows three distinguishable stages which has the similar evolution trend with the floating potential V f on the RFEA frontplate: (i) the stable stage with two high-energy peaks (E 2 and E 3 with energy respectively lower and higher than the applied U + amplitude) when the floating potential V f is close to the applied positive pulse voltage; (ii) the transition stage with low-energy populations when the V f drops by ∼20 V within ∼10 μs; and (iii) the oscillation stage with alternating E 2 and E 3 populations and ever-present E 1 population when the V f slightly decreases until to the end of positive pulse. The comparison of IVDFs in BP-HiPIMS and ACBP-HiPIMS suggests that both the mean ion energy and high-energy ion flux have been effectively improved in ACBP-HiPIMS discharge. The formation of floating potential drop is explored using the Langmuir probe which may be attributed to the establishment of anode double layer structure. The acceleration of ion at the double layer boundary is analysed using a theoretical model, in this way to clarify the oscillation in IVDF evolutions in ACBP-HiPIMS discharge.

Bipolar nano-second pulse power supply for electrochemical micromachining of tungsten carbide without tool wear

Electrochemical machining (ECM) of tungsten carbide (WC) alloy using bipolar pulses with a neutral electrolyte (NaNO3 aq) was successfully proposed in recent years. However, tool electrode wear always occurs during machining in the period of negative pulses. To solve this problem, a method of ECM with sacrificial auxiliary electrode using bipolar current is presented. This paper is focusing on the development of nano-second pulse bipolar power supply for this method. Firstly, positive and negative nanosecond pulses are obtained with the method of DC voltage chopping by using a multi-channel high-speed switch composed of gallium nitride (GaN) transistors. Then, these pulses are accordingly distributed onto the electrodes between tool electrode, workpiece electrode and auxiliary electrode during ECM in different time. During the period of positive pulses, the workpiece anode and tool cathode form a circuit for ECM, which dissolve the workpiece and form a passive film (tungsten oxide) on tungsten carbide; during the period of negative pulses, the workpiece cathode forms a loop with the auxiliary anode, resulting in hydrogen evolution reaction on the surface of workpiece, so as to weaken the adhesion of the passive film and improve the pH value of the electrolyte close to the machining area on workpiece surface to dissolve the tungsten oxide. ECM experiments were carried out with the developed power supply, and the micro holes are successfully machined on the surface of tungsten carbide without tool wear, which verifies the feasibility of the presented method and designed bipolar pulse power supply.

Plasma flux and energy enhancement in BP-HiPIMS discharge via auxiliary anode and solenoidal coil

As an emerging and extraordinary plasma source, the bipolar-pulse high power impulse magnetron sputtering (BP-HiPIMS) has promising prospects and wide industrial applications. In this paper, an effort to optimize the plasma flux and energy in BP-HiPIMS via auxiliary anode and solenoidal coil was made. This novel plasma source contains two types of auxiliary anode voltage (direct current and pulse) and one type of solenoidal coil current (direct current) to synergistically enhance the plasma generation and diffusion by electric field and magnetic field together. Systematic evaluations of discharge characteristics demonstrate that applying auxiliary anode voltage and coil magnetic field effectively contribute to a reduction in delay time of target current onset and increase in peak amplitude of target current, which are beneficial for improving plasma generation and target sputtering. The complex plasma dynamics are diagnosed by Langmuir probe and optical emission spectroscopy, and simulated by particle-in-cell/Monte Carlo collision approach. These comprehensive investigations on plasma parameters demonstrate that the plasma density, emission intensity of the metal ions, substrate current density, and ionization fraction of sputtered target particles have been improved with the increase of coil current. The observations of the increase in excitation temperature T exc of Ar atoms, and more extended high-energy tails in electron energy distribution function curves imply that the plasma can be significantly heated by the auxiliary anode. Combining the simulation results and theoretical model proposed in the last sub-content, the diffusion and transport mechanism of charged-particles in complex electric and magnetic fields are discussed. From the theoretical analysis, the qualitative relation between the plasma density and coil current is well consistent with the measurements of electron density obtained by Langmuir probe. These evidences all support the idea that the plasma flux and energy can be enhanced in BP-HiPIMS discharge via auxiliary anode and solenoidal coil together.

Optimizing the ion diffusion in bipolar-pulse HiPIMS discharge (BP-HiPIMS) via an auxiliary anode

The investigation of plasma dynamics and optimization of target particle diffusion are particularly important and urgent in the recently emerging bipolar-pulse high-power impulse magnetron sputtering (BP-HiPIMS) discharge. In this paper, a novel approach, in which an external auxiliary anode was installed in front of the sputtering target, was proposed to optimize electric field distribution and guide particle diffusion, named as AABP-HiPIMS. A positive pulse voltage was applied to the auxiliary anode in synchronization with the target positive pulse voltage, which was achieved by connecting the target and auxiliary anode through a diode in series. Advantageously, no additional power supply needs to be provided in AABP-HiPIMS. The discharge characteristics of this new plasma source were investigated in detail. A theoretical model was successfully built to reveal the transformation process of the target current from the net ion current to the net electron current by systematically analyzing the collapsing process of the target sheath and charged-particle movement in E × B fields. The optimization of ion diffusion was investigated by diagnosing plasma parameters using a Langmuir probe and emissive probe together. The measurements illustrate that, as expected, the electron density in AABP-HiPIMS during the positive pulse phase has been effectively increased ∼2.5 times on average compared to that in the conventional BP-HiPIMS. Correspondingly, the plasma potential distribution illustrates that the potential gradient pointing to the auxiliary anode centre is more beneficial for control of ion diffusion and to enhance ion flux towards the downstream. Additionally, for better selection of the magnetron process parameters, the characteristic time of plasma decay during the positive pulse was estimated using the Bohm diffusion theory. The rough calculation of flight time for electrons from z = 35 to 95 mm was ∼70 μs in BP-HiPIMS and ∼50 μs in AABP-HiPIMS, respectively. The effects of negative pulse duration and positive pulse amplitude on plasma parameters were investigated. Measurements of plasma potentials suggest that adopting a relatively short duration negative pulse and a slightly higher amplitude positive pulse, as well as employing the externally applied auxiliary anode, are the optimum choices for improving both the flux and energy of deposited particles when preparing films on the floating substrate.

Electron beam generation in an arc plasma source with an auxiliary anode plasma

In a plasma-cathode electron source with a grid-stabilized emission boundary, a discharge in crossed fields was used to create an auxiliary anode plasma before the generation of an electron beam. Such a plasma formed in the beam transport region shortens the rise time of the beam current and eliminates or at least minimizes its high-frequency oscillations at low pressures, making possible electron beams of several microseconds long and stable lower-pressure modes with less probable acceleration gap breakdowns. These effects are explained primarily by gas pre-ionization in the beam acceleration and transport region and by ion flows from the acceleration gap to the plasma cathode of the source.

Improving the performance of biotrickling filter microbial fuel cells in treating exhaust gas by adjusting the oxygen content of the anode tank

A biotrickling filter (BTF) was combined with a microbial fuel cell (MFC) to remove ethyl acetate from exhaust gas while generating electricity in the process. The results indicated that the use of carbide porous ceramic rings (CPCR) as auxiliary anodes produced more biomass and exhibited a high average removal efficiency (98%), making it a superior microorganism growth carrier compared with carbon coke. When CPCR was used as the cathode in the BTF-MFC, the maximum power density (PD) was 5.64–14.8% of that achieved when carbon cloth was used as the cathode, revealing that CPCR is not a suitable cathode. The maximum elimination capacity (EC) and output voltage of the two-stage BTF-MFC (tBTF-MFC) were only 69.4% and 68.4% of those of the single-stage BTF-MFC (sBTF-MFC), presumably because of voltage reversal. Although the output voltage and EC in the tBTF-MFC were less than those in the sBTF-MFC, the follow-up field application involves stacking multiple small MFCs to remove high-concentration pollutants and generate a high power output. Additionally, continuously adding sodium sulfite decreased the average dissolved oxygen; generated an averaged closed-circuit voltage of 477 mV; and produced a maximum PD of 71.7 mW/m3. These findings demonstrated that the aforementioned method can effectively improve the problem of oxygen and MFC anodes competing for electrons, thus delivering a method that enhances MFC performance through controlling the amount of oxygen in practical applications.

A new design of substation grounding based on electrolytic cathodic protection and on transfer corrosion current

In this paper, zinc material is used as auxiliary anode grounding electrode and connected by flat steel to form grounding grid of electrolytic cell protection circuit, to prevent the main grounding grid from corrosion. At the same time, the paper designs to transfer the lead-down from the grounding grid to the auxiliary anode grounding grid, and to transfer the corrosion current to the auxiliary anode grounding grid. Several groups of zinc-iron electrodes were deeply buried in deep excavated soil outdoors to conduct simulated grounding grid protection tests. At the same time, the software simulation is carried out in the laboratory. Firstly, Rotating Disk Electrode (RDE) and Solartron electrochemical interface were used to compare the current-voltage curves of three cases (natural anode, passive cathode and active cathode), and the corrosion rates of the three cases were calculated. Secondly, ATP-EMTP simulation software is used to simulate the point voltage and current of the auxiliary anode grounding grid before and after the design of the transfer corrosion current. The simulation results show that passive electrolytic cathode has better corrosion protection. The auxiliary anode grounding grid design and the transfer corrosion current design can better prevent the main grounding grid from corrosion.