Ion Diffusion Coefficient Research Articles

Numerical Investigation of Sulfate Diffusion Characteristics in Recycled Aggregate Concrete Based on Mesoscale Multiphase Analysis

Sulfate-induced deterioration can reduce the service life of recycled aggregate concrete (RAC). To demonstrate the transport behavior of sulfate ions in RAC, a two-dimensional, six-phase numerical model of RAC is proposed in this study. Sulfate ion diffusion coefficients were defined for different phases [attached mortar, new mortar, interfacial transition zone (ITZ) between attached mortar and original aggregate, ITZ between the new mortar and original aggregate, and ITZ between the new mortar and attached mortar] of RAC. The effects of ITZ width and porosity on ion transport behavior in RAC were analyzed. The results show that the numerical model agrees with the experimental data. Numerical results indicate that the six-phase model of RAC provides more-accurate simulation results because tortuosity is reflected in the model. The width and porosity of ITZs both affect the diffusion of sulfate ions in concrete. However, due to the low volume fraction of ITZ in concrete, just improving ITZ performance has no significant effect on ion attack resistance of concrete. The ITZ is a crucial zone where damage may originate and develop.

Investigation of Hexylamine Adsorption on Gold in Perchloric Acid

The adsorption of hexylamine at the solution–gold interface in 1 M HClO4 in the presence of 0.1 M Fe2+ and 0.1 Fe3+ was studied by potentiodynamic, chronoamperometric and EIS methods. The main kinetic characteristics of the oxidation-reduction reaction iron ions (exchange current density, transfer coefficient, diffusion coefficients of iron ions) were determined. It was shown that the physical adsorption of hexylamine on gold can be described by the Dhar–Flory–Huggins isotherm. The values of the adsorption constant and the Gibbs free adsorption energy were obtained. A comparison of the free adsorption energy at these interfaces with the interaction energies of hexylamine and water molecules, and hexylamine molecules with each other was carried out. It was shown that hexylamine adsorption at all of these interfaces is due mainly to the hydrophobic effect of the interaction of hexylamine and water molecules.

Determination Method of Diffusion Coefficient in a Neat Redox-Active Ionic Liquid at a Microdisk Electrode in the Domains Ranging from the Steady-State to Potentiodynamic Near-Steady-State.

In redox-active ionic liquids (RAILs), either or both of the constituent ions are redox-active. Because of the high concentration of the ions, RAILs exhibit not only ion conduction but also electron conduction through the bimolecular electron self-exchange reaction. Because neat RAILs do not contain any supporting electrolyte, migration of the redox active ions results in enhancement or diminishment of the redox current at an electrode. To treat the migration effect for electrochemical analysis, a limiting current correction was theoretically derived by Oldham, Hyk, and Stojek (Oldham, K. J. Electroanal. Chem. 1992, 337, 91-126; Hyk, W.; Stojek, Z. Anal. Chem. 2002, 747, 4805-4813) for the steady-state voltammetry. Although steady-state voltammetry is a robust method in electrochemistry, the actual measurement is time-consuming and cannot be always made because of the instability of the electrochemical system. To overcome the problem, we propose the use of cyclic voltammetry to evaluate the diffusion coefficient of the redox-active ion that constitutes RAIL. The peak currents were analyzed by the purely diffusional framework of the Aoki-Matsuda-Osteryoung equation (Aoki, K.; Akimoto, K.; Tokuda, K.; Matsuda, H.; Osteryoung, J. J. Electroanal. Chem. 1984, 171, 219-230.) in the range from several mV s-1 to several ten mV s-1, and the migration correction to the near-steady-state limiting current was applied on the basis of the Oldham-Hyk-Stojek theory to scale the diffusion coefficient. As an example of RAILs, [FcC6ImC1][TFSI], which exhibits charge increase reaction with the same sign (S+ - e- ⇌ P2+), was used and the cyclic voltammograms were recorded at various sizes of the microdisk electrodes and various scan rates. The peak currents obeyed the Aoki-Matsuda-Osteryoung equation with the scaled diffusion coefficient, which has the same value as determined by the steady-state voltammogram. Our approach can be used to evaluate the diffusion coefficient of redox-active ions that constitute the RAIL with the charge increase reaction with the same sign.

ELECTROCHEMICAL REDUCTION OF CADMIUM IONS FROM ETHYLENE GLYCOL ELECTROLYTE

The work is devoted to the study of the process of cathodic reduction of Cd ions from anhydrous ethylene glycol electrolyte. The mechanism of the process of cadmium reduction was studied by taking linear and cyclic potentiodynamic polarization curves. The influence of cadmium chloride concentration, potential sweep rate and temperature on the process of electrochemical deposition of cadmium ions was studied. With an increase in the concentration of cadmium in the electrolyte, the rate of its release at the cathode increases. Precipitates of good quality are obtained at current densities of 25 mA/sm2. It has been established that the cadmium deposition potential almost does not change with increasing potential sweep rate. The dependence of cadmium electrodeposition from ethylene glycol electrolyte on temperature was studied, which made it possible to establish the optimal deposition temperature, which was 363–373 K, and to conclude that the deposition process is controlled by electrochemical polarization. The diffusion coefficient of cadmium ions to the cathode surface has been calculated

Molecular dynamics study on the adsorption of radioactive ions by geopolymers

The construction of nuclear power plants necessitates careful consideration of the discharge and fixation of nuclear waste. Geopolymers are new cement-based materials (CBMs) with three-dimensional cage-like structures that enable effective nuclear waste fixation. In this work, the adsorption of radioactive caesium and strontium ions by sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymers, was investigated using molecular dynamics simulations to obtain nanoscale insights into the ions’ interactions with the gel. The formation of strong ion–oxygen bonds allowed both ions to be effectively adsorbed on the NASH surface, but the adsorption ratio of strontium ions (17.2%) was slightly lower than that of caesium ions (21.0%). Because strontium ions are divalent, they can form stronger electrostatic interactions with water molecules and chloride ions, which hinders their approach to the interface. For the same reason, the diffusion coefficient of strontium ions in solution is lower than that of caesium ions. These results provide new insights into the nuclear waste fixation capacity of NASH gel and guidance for the design of new CBMs for radioactive waste disposal.

The durability of basalt-fiber-reinforced cement mortar under exposure to unilateral salt freezing cycles

Basalt fiber and cement-based materials have been widely applied in engineering structures. In this context, the durability of basalt-fiber-reinforced ordinary silicate mortar was systematically studied under exposure to unilateral salt freezing. The mechanical durability, chloride ion diffusion characteristics, and microscopic pore characteristics of cement mortar with basalt fiber content levels in the range of 0 kg/m3–1.5 kg/m3 were tested under exposure to 0–40 freeze–thaw cycles. The relationships of changes in the internal pore structure with mass loss, mechanical damage, and the physical properties of the material were also analyzed under exposure to salt freezing cycles. The results demonstrated that even a small amount of basalt fiber could significantly improve the mechanical properties of cement mortar under unilateral salt freezing and its resistance to salt freezing erosion. In particular, cement mortar with 1.2 kg/m3 basalt fiber content exhibited good durability of compressive and flexural strength, while the specimens with no basalt fibers exhibited a relatively large degree of internal porosity under exposure to unilateral salt freezing. Our work provides concrete evidence for changes in the porosity of mortar under exposure to unilateral salt freezing, with these changes showing an exponential relationship with mortar mass loss and a strong linear correlation with changes in the compressive strength, flexural strength, and chloride ion diffusion coefficient of the material.

Enhanced Electrochemical Performance of a Ti-Cr-Doped LiMn1.5Ni0.5O4 Cathode Material for Lithium-Ion Batteries.

Ti, Cr dual-element-doped LiMn1.5Ni0.5O4 (LNMO) cathode materials (LTNMCO) were synthesized by a simple high-temperature solid-phase method. The obtained LTNMCO shows the standard structure of the Fd3®m space group, and the Ti and Cr doped ions may replace the Ni and Mn sites in LNMO, respectively. The effect of Ti-Cr doping and single-element doping on the structure of LNMO was studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) characteristics. The LTNMCO exhibited excellent electrochemical properties with a specific capacity of 135.1 mAh·g-1 for the first discharge cycle and a capacity retention rate of 88.47% at 1C after 300 cycles. The LTNMCO also has high rate performance with a discharge capacity of 125.4 mAh·g-1 at a 10C rate, 93.55% of that at 0.1C. In addition, the CIV and EIS results show that the LTNMCO showed the lowest charge transfer resistance and the highest diffusion coefficient of lithium ions. The enhanced electrochemical properties may be due to a more stable structure and an optimized Mn3+ content in LTNMCO through TiCr doping.

Numerical and experimental analysis of chloride and iodide transports in concrete under natural diffusion

This study investigates the natural diffusion laws of chloride ions and iodide ions in concrete and proposes their correlations during the process of diffusion. By measuring the free ion concentration at different exposure times and diffusion depths, time-varying laws related to the ion diffusion coefficient D and surface ion concentration Cs were proposed. The linear proportional relationship between two kinds of ions is explored and fills the relevant research gaps. Natural diffusion models of ions are established via the finite element software COMSOL and the adjustment parameters K and λ are innovatively proposed. Thus, this enables the effective conversion of the ion resistance permeability coefficients measured by the RCM and RIM methods, especially for the concrete containing chloride. The results of numerical calculation and experimental measurement have a strong correlation. Furthermore, a two-dimensional concrete model with different aggregates is used to simulate the ion diffusion characteristics. It is confirmed that the increase in aggregate volume ratio and tortuosity inhibited ion diffusion, and the ion concentration in the local area was greatly reduced.

Sm2O3 coating to suppress electrode/electrolyte side reactions of single crystal materials at high voltage

Coating modification of single-crystal materials was studied to improve the electrochemical properties of the materials by suppressing the electrode/electrolyte side reactions. The commercial LiNi0·6Co0·1Mn0·3O2 was used as the base material and Sm2O3 coating was applied on its surface. The Sm2O3-coated NCM613 single-crystal material was synthesized. The structure and morphology of the electrode materials were characterized by XRD, FESEM, and TEM. The results showed that Sm2O3 was successfully coated on the surface of the particles without damaging the original structure of the material. Meanwhile, the lithium ions diffusion kinetics of the material was analyzed by cyclic voltammetry. The results show that the coated cathode material has a more excellent lithium ions diffusion coefficient, which provides a kinetic basis for charging and discharging the battery at high voltage. At 25 °C, 3.0−4.5 V, and 1 C current density, the capacity retention of the coated cathode material after 100 cycles was 87.5% (182.8−159.9 mAh g−1), which was much higher than that of the original material at 77% (177−136.3 mAh g−1). SEM and other characterizations of the electrode sheets after cycling showed that the Sm2O3 coating layer effectively prevented the direct contact between the cathode material and the electrolyte, which played a positive role in suppressing the occurrence of side reactions, and inhibits the formation of microcracks during the cycling process. In general, this method contributed to the stability of the electrode/electrolyte interface and electrochemical performance.

Self-healable polymer complex with a giant ionic thermoelectric effect

In this study, we develop a stretchable/self-healable polymer, PEDOT:PAAMPSA:PA, with remarkably high ionic thermoelectric (iTE) properties: an ionic figure-of-merit of 12.3 at 70% relative humidity (RH). The iTE properties of PEDOT:PAAMPSA:PA are optimized by controlling the ion carrier concentration, ion diffusion coefficient, and Eastman entropy, and high stretchability and self-healing ability are achieved based on the dynamic interactions between the components. Moreover, the iTE properties are retained under repeated mechanical stress (30 cycles of self-healing and 50 cycles of stretching). An ionic thermoelectric capacitor (ITEC) device using PEDOT:PAAMPSA:PA achieves a maximum power output and energy density of 4.59 μW‧m−2 and 1.95 mJ‧m−2, respectively, at a load resistance of 10 KΩ, and a 9-pair ITEC module produces a voltage output of 0.37 V‧K−1 with a maximum power output of 0.21 μW‧m−2 and energy density of 0.35 mJ‧m−2 at 80% RH, demonstrating the potential for a self-powering source.

Effect of doping ferroelectric BaTiO3 nanoparticles on dielectric, electro-optical, and ionic properties of antiferroelectric bent-core liquid crystal

Nano-doping in polar bent-core liquid crystals is the topic of current interest for designing multifunctional smart materials. Here, we study the effect of doping of two different-sized (5–15 nm and 50–70 nm) ferroelectric BaTiO3 nanoparticles on the dielectric, electro-optical and ionic properties of antiferroelectric smectic A bent-core liquid crystal. Doping with both the sizes of nanoparticles results in lowering of the transition temperature of the liquid crystal mesophases. Both, the pure as well as doped samples show a soft mode in their antiferroelectric smectic A phase. In comparison to pure liquid crystal, the dielectric strength of the soft mode in doped samples is decreased, while their relaxation frequencies show an increasing behavior. Additionally, a decrement has been observed in the spontaneous polarization of the doped samples. A drop in polarization as well as soft mode dielectric strength values in doped samples, simultaneously point to an antiparallel dipole–dipole correlation between the ferroelectric nanoparticles and antiferroelectric liquid crystal molecules. Higher values of molecular mode relaxation frequencies obtained in nano-doped samples indicate a decrement in viscosity and dilution of pure liquid crystal. An important electro-optical parameter, the response time shows a remarkable decrement for the higher size (50–70 nm) nanoparticles doped sample. An enhancement in direct current conductivity and ion diffusion coefficient is observed for both the nano-doped samples. The smaller size (5–15 nm) ferroelectric nanoparticles reduce the mobile ion concentration and act as ion-capturing agents for the liquid crystal. A systematic investigation of the nano-doped bent-core liquid crystal can catalyze the use of the combined media for faster switching electro-optic applications.

Deicing performance of cement pavement concrete mixed with chlorine salt antifreeze material

This study explores a cost-effective and efficient method for snow melting and deicing using a concrete pavement structure with pre-mixed chloride-salt antifreeze material. The mixed design method for road cement concrete with chloride-type antifreeze material is investigated by encapsulating NaCl and CaCl2 in organic resin capsules. The snow melting and deicing efficacy of cement concrete with chloride antifreeze material is evaluated through an automatic tracking measurement system. The results indicate that NaCl-type antifreeze material is more effective in reducing the freezing point of concrete surface solution than CaCl2-type antifreeze material. A composite antifreeze material (4% NaCl + 1% CaCl2) provides the strongest snow melting and deicing ability. An outward migration and diffusion model of chloride ion in cement concrete with antifreeze material is established to calculate the chloride ion diffusion coefficient, surface chloride ion content, and decay rate of concrete. The effective age of snow melting and deicing is analyzed using this model.

Cellulose as a novel precursor to construct high-performance hard carbon anode toward enhanced sodium-ion batteries

Cellulose, as it has high content and low cost along with the absence of heteroatoms, can well balance the cost and structural consistency issues raised by mass production. Herein, the cellulose-derived hard carbon as an anode material for sodium-ion batteries with high performance has been prepared by a one-step direct carbonization process using pure cellulose as a precursor in the temperature range of 900–1400 °C. Moreover, the effect of carbonization temperature on the microstructure and the sodium battery storage properties of cellulose-derived hard carbon was investigated by structural and morphological characterization, as well as electrochemical performance testing. The results show that the CHC-1300 electrode material displays a high reversible capacity of 373.2 mAh g−1 at 30 mA g−1, and exhibits a desirable cycling stability with 89.7 % capacity retention even after 200 cycles. Furthermore, cyclic voltammetry technique (CV) at different scan rates and galvanostatic intermittent titration technique (GITT) have been employed to explore the sodium storage mechanism and sodium storage kinetics of cellulose-derived hard carbon. The results exhibit that the rate performance of the electrode material would be affected by the low apparent diffusion coefficient of sodium ions in the plateau region. Besides, a full-cell has been assembled with CHC-1300 as the anode and Na0.83Mg0.11Ni0.22Mn0.63O2 (NMNM) as the cathode. The CHC-1300//NMNM full-cell shows high energy density and good cycling stability, which could verify the practical application of the cellulose-derived hard carbon.

Kinetic Analysis of Sodium-Ion Intercalation Reaction into Graphene-Like Graphite by Electrochemical Impedance Spectroscopy

Graphene-like graphite (GLG) is a promising anode material for sodium-ion batteries, which is believed to have unique kinetic properties compared to hard carbon due to its different intercalation mechanism. In this study, electrochemical impedance spectroscopy was used to investigate the kinetic properties of sodium-ion intercalation in GLG. Our results indicated that the activation energies for interfacial sodium-ion transfer of GLGs were nearly identical to those reported for graphite, regardless of the heat treatment temperature of the GLGs. Furthermore, these activation energies were lower than those observed for hard carbon, suggesting better sodium-ion intercalation kinetics. In addition, the diffusion coefficient of sodium ions in the GLG was similar to that of graphite, with the highest value observed for GLG800, the GLG heat-treated at the highest temperature of 800 °C. This may indicate that the diffusion coefficient increases with the presence of nanopores in the graphene layer of GLG. It has also been reported that GLG800 is superior in terms of reversible capacity and working potential compared to GLGs synthesized at other temperatures. Consequently, the results clearly demonstrated that GLG800 has the best electrochemical properties in terms of both thermodynamics and kinetics among the GLGs investigated in this study.

Statistical uncertainty quantification to augment CDI electrode design and operation optimization

Capacitive deionization (CDI) is considered to be one of the most promising technologies to deionize water with low/medium concentration. Great attention has been paid to improve its performance by optimizing electrode architectures and operation conditions. However, no guidelines are built for developing such strategies due to the nonlinear impact of the parameters concerning electrodes and operations. Therefore, our work quantitatively reveals the influence of some key parameters involving electrode characteristics, operation conditions and ion properties using the statistical analysis based on uncertainty quantification. We find the porosity solely has a small influence on all the performance metrics. But the pore might play a significant role by the pore size distribution and connectivity that greatly determine the effective diffusion coefficient of salt ions. The high diffusion coefficient obviously raises the salt adsorption by facilitating ion transport, which also reduces the energy consumption while most of the consumed energy could even be recovered. The current exerts an opposite influence by shortening the charging period in the constant current (CC) mode. The salt concentration in the inflow water increases the adsorption capacity but decreases the removal efficiency. The decreased removal efficiency requires less external energy, enabling the usage of CDI as an economic pre-treatment unit. We highlight the ion transport resistance and its influence on CDI performance by acting upon charging time in the CC mode. We also suggest the application of the constant voltage mode to the low-salinity wastewater instead of the CC mode due to the high resistance. Our work addressed the importance of proper electrode and operation condition for high desalination performance and energy efficiency.

An inexpensive preparation of unique nano-micro porous LiFePO4 cathode with excellent rate capability for lithium-ion batteries

The application of LiFePO4 cathode material in the field of power lithium-ion batteries is seriously hampered by its poor rate performance that is triggered by its inherent poor electrical conductivity and low ion diffusion coefficient. Herein, an inexpensive and facile preparation method is developed to fabricate a novel nano-micro porous structural LiFePO4 cathode using 30 nm carbon black and iron powder as direct raw materials. It is found that the added amount of carbon black is an important factor affecting the phase and morphology of the products. Optimizing the amount of carbon black, the LiFePO4 cathode with the unique nano-micro porous structure and high specific surface area could be obtained. Such unique porous architecture with a high specific surface area can accelerate lithium-ion diffusion during charge/discharge to promote its rate performance. Meanwhile, the residual graphitized carbon derived from carbon black can not only enlarge the surface pseudocapacitance under high C rates but also enhance its electronic conductivity. Benefit from the suitable pseudocapacitive behavior and high Li+ diffusion coefficient, the LFP-1.5 electrode exhibits a discharge specific capacity of 166.27 mAh/g at 0.1C and 124.95 mAh/g at 20C, indicating prominent discharge specific capacity and excellent high-rate charge/discharge capability.

Micropore-facilitated surface-dominated pseudocapacitive storage in MOF-derived hollow nano-cuboids enabled by in-situ Zn-sacrificed strategy

Herein, we report a novel metal–organic frameworks (MOF)-derived nanomaterial, this is hollow nano-cuboids composed of NiCoP particles and nanocarbon, which is enriched in appropriate micropores induced by in-situ Zn-sacrificed strategy (NiCoP@C(Zn)). Such abundant micropores (∼0.5 nm, larger than the radius of OH−) can supply more ion shuttle channels at multi-directions, greatly-reducing the longitudinal migration time in the hollow structure, resulting in a rather high ion diffusion coefficient (∼10−8 cm2 s−1). This combined with hollow topology show the marked electrolyte-accessibility recognized by experimental and density functional theory (DFT) results, which can adequately-expose the electrochemically active sites, thus birthing a surface-dominated pseudocapacitive behaviors towards high-rate response and high-capacity storage. Due to the robust structural merits and pore character as well as their synergy, the NiCoP@C(Zn) electrode can realize a rather stable cyclability (over 10,000 cycles). Further, we construct the pouch-type supercapacitor based on NiCoP@C(Zn) cathode, which delivers a relatively-good energy output (35.2 Wh kg−1), superior to those of some previously-reported asymmetric supercapacitors. Remarkably, such pouch device can exhibit the triple-high properties, including high mechanical reliability, high safety and high availability in real-word application. This work successfully-discloses the influence of well-matched micropores on pseudocapacitive charge storage, and opens new horizons of developing a high-performance electrode nanomaterial.

Microscopic-Level Insights into Solvation Chemistry for Nonsolvating Diluents Enabling High-Voltage/Rate Aqueous Supercapacitors.

Localized "water-in-salt" (LWIS) electrolytes are promising candidates for the next generation of high-voltage aqueous electrolytes with low viscosity/salt beyond high-salt electrolytes. An effective yet high-function diluent mainly determines the properties of LWIS electrolytes, being a key issue. Herein, the donor number of solvents is identified to serve as a descriptor of interaction intensity between solvents and salts to screen the organic diluents having few impacts on the solvation microenvironment and intrinsic properties of the original high-salt electrolyte, further leading to the construction of a novel low-viscosity electrolyte with a low dosage of the LiNO3 salt and well-kept intrinsic Li+-NO3--H2O clusters. Nonsolvating diluents, especially acetonitrile (AN) that has never been reported previously, are presented with the capability of constructing a LWIS electrolyte with nonflammability, electrode-philic features, lower viscosity, decreased salt dosage, and a greatly enhanced ion diffusion coefficient by about 280 times. This strongly relies on a huge difference of about 5000 times in coordination and solubility between AN and H2O toward LiNO3 (0.05 vs 25 mol kgsolvent-1) and the moderate interaction between AN and H2O. Multi-spectroscopic techniques and molecular dynamics simulations uncover the solvation chemistry at the microscopic level and the interplay among cations, anions, and H2O without/with AN. The identified unique diluting and nonsolvating effects of AN reveal well-maintained cation-anion-H2O clusters and enhanced intermolecular hydrogen bonding between AN and H2O, further reinforcing the H2O stability and expanding the voltage window up to 3.28 V. This is a breakthrough that is far beyond high-viscosity/salt electrolytes for high-voltage and high-rate aqueous supercapacitors.

Ionic transport and segmental dynamics in poly(ethylene oxide) based polymer electrolytes: Dependence on molecular weight of host polymer matrix

We have investigated the ion transport and segmental dynamics in poly(ethylene oxide) (PEO) and sodium tetrafluoroborate (NaBF4) salt based solid polymer electrolytes as a function of molecular weight of PEO polymer matrix at a fixed salt concentration (EO/Na = 18) using broadband dielectric spectroscopy. The molecular weight (Mv) of PEO polymer matrix was varied from 1 × 105 to 6 × 105 g/mol. The ionic conductivity of the PEO based electrolytes obtained from the complex impedance plot showed a correlation with the glass transition temperature, crystallinity and ion diffusion coefficient. The AC conductivity spectra were analyzed by using the universal power law model, except the low frequency region, where the electrode polarization contribution was dominant. The temperature dependence of ionic conductivity and the hopping frequency followed the Vogel-Tammann-Fulcher (VTF) relation, indicating a coupling between the ion transport and the segmental dynamics of polymer chains. The segmental dynamics was investigated using the derivative dielectric constant spectra. The modulus spectra were well described by the Havriliak-Nigami and the Kohlrausch-Williams-Watts functions. The temperature dependence of the conductivity relaxation time also followed the VTF relation. The ion transport in PEO based polymer electrolytes with higher molecular weight was found more cooperative than that of the other polymer electrolytes.

Protective Performance of Coated Reinforcement in Coral Concrete under Dry/Wet Cycling.

The actual protective performance of the coated reinforcement in coral concrete was investigated by measuring the chloride ion diffusion coefficient, electrochemical analysis, and numerical simulation. The test results show that the corrosion rate of coated reinforcement in coral concrete under the action of wet and dry cycles is kept at a low level, and the Rp value is always greater than 250 kΩ·cm2 during the test period, which is in the uncorroded state and has good protection performance. Moreover, the chloride ion diffusion coefficient D is in accordance with the power function relationship with the wet and dry cycle time, and a time-varying model of chloride ion concentration on the surface of coral concrete is established. The surface chloride ion concentration of coral concrete reinforcement was modeled as a time-varying model; the cathodic zone of coral concrete members was the most active, increasing from 0 V to 0.14 V from 0 to 20 years, with a large increase in potential difference before the 7th year, and a significant decrease in the increase after the 7th year.