NaCl Deposit Research Articles

Corrosion behavior of Ti60 alloy under continuous NaCl solution spraying at 600 °C

• The corrosion rate of Ti60 alloy in NaCL spray is lower than that under NaCL film. • A mixed corrosion including classical oxidation and active oxidation happened. • The mixed corrosion delayed active oxidation and formed dense Ti oxides scale, both of which decreased corrosion rate. The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600 °C. Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit film in H 2 O + O 2 . The outer corrosion products are compact layers mainly containing Na 2 TiO 3 and nanocrystalline TiO 2 . The inner layer is mainly composed of Ti 2 O, TiO and SnO 2 . Ti 2 O has a lamellar structure, and TiO has a strip-shaped structure. A mixed corrosion mechanism including classic oxidation and active oxidation occurred under NaCl solution spraying environment: the first stage was controlled by the classic oxidation mechanism with the promotion by the active oxidation following parabolic curves, and the second stage was controlled by the active oxidation mechanism following a linear rise in the mass gain curve. The mixed corrosion mechanism between classic oxidation and active oxidation produced a relatively dense Ti oxides scale, which decreased the corrosion rate.

Pore-Scale Micro-Structural Analysis of Electrode Conductance in Metal Displacement Batteries

Metal displacement batteries (MDBs), or liquid metal batteries, are an emerging technology with significant potential in providing high capacity, low-cost energy storage solutions, capable of addressing many of the challenges associated with storing energy from renewable sources. The key characteristic of metal displacement batteries is that at least one of the electrodes is in liquid state and a molten salt is used as an electrolyte. Since its original proposal in the 1960’s liquid metal batteries have re-emerged in recent years and different battery chemistries and designs have been explored, including Ca-Bi, Na-Sb, and many others [2,10]. Recently, Na-Zn liquid metal batteries have been studied as an alternative to other configurations, showing significant potential in achieving good performance for large-scale energy storage, while avoiding the high cost associated with some electrode materials such as Nickel or Lithium [7,8]. In past years, alternatives to all-liquid cells have emerged in the form of designs where the cell materials are a mixture of solids and liquids. Examples of this include the commercially available Zebra battery, where a Na-NiCl electrode pair is used [1,6]. These designs offer some of the advantages of all-liquid cells, while simultaneously mitigating many of the disadvantages of handling and operating a very high temperature system. Na-Zn have also been proposed for solid cathode designs, taking advantage of the lower cost of Zn over Ni [4,3].The cathode in these designs is composed of a porous structure, within which multiple chemical species can co-exist. Electrolyte components share the space with metal deposits,salt crystals, and other electrochemical reaction products. As a result, the micro-porous structure of this composite system is an important factor in determining the performance of the cell, as the spatial distribution of different materials can have an impact on the effective conductivity of the electrode [5,9]. The porous structure hosts complex multi-component mass transfer phenomena as well, potentially having an impact on the mass-transfer overpotential of the cell.This work aims to study the impact of the microstructural properties of the solid electrode in a liquid displacement battery, and their importance to the effective conductivity of the system. We have developed a computational tool that enables us to create randomized microstructures in 3D, representing the electrode-electrolyte assembly. We are able to preserve the desired physical characteristics by using target pore-size distributions and volume fraction input as seed parameters. We use this tool to generate representative structures and analyze their effective bulk conductivity by solving Laplace’s equation over the resulting domain, accounting for the different local conductivity of each material.This methodology is applied to a novel Na-Zn cell in order to assess the importance of the pore-scale properties of the cathode, as well as its material components, including solid Zn metal, solid NaCl deposits, and molten salt components. It is expected that different material arrangement configurations will induce heterogeneous current distributions in this system. Furthermore, the ionic composition of the electrolyte would be different at different charge levels, leading to additional variation through its charge/discharge cycle.Using this methodology, the range of different electrode phase configurations produced during operation can be studied in the absence of microstructure imaging data. A representative elementary volume for the Zn electrode assembly is analyzed to determine the best approach for up-scaled performance predictions of the Na-Zn cell. With this method, it is possible to acquire data to elucidate desirable or undesirable electrode structure properties of this system, providing insight which can be used for improving manufacture and operation of the cell. [1] Dustmann. “Advances in ZEBRA batteries”. J. Power Sources (2004).[2] Kim et al. “Liquid metal batteries: Past, present, and future”. ChemicalReviews (2013).[3] Lu et al. “An Intermediate-Temperature High-Performance Na-ZnCl2 Bat-tery”. ACS Omega (2018).[4] Lu et al. “Liquid-metal electrode to enable ultra-low temperature sodium-beta alumina batteries for renewable energy storage”. Nature Communications(2014).[5] Qiu et al. “Pore-scale analysis of effects of electrode morphology and electrolyteflow conditions on performance of vanadium redox flow batteries”. J. PowerSources (2012).[6] Sudworth. “The sodium / nickel chloride ( ZEBRA ) battery”. J. Power Sources (2001).[7] Xu et al. “Electrode Behaviors of Na-Zn Liquid Metal Battery”. Journal ofThe Electrochemical Society (2017).[8] Xu et al. “Na-Zn liquid metal battery”. Journal of Power Sources (2016).[9] Zhang et al. “Progress in 3D electrode microstructure modelling for fuel cellsand batteries: transport and electrochemical performance”. Progress in Energy(2019).[10] Zhang et al. “Liquid Metal Batteries for Future Energy Storage”. EnergyEnvironmental Science (2021). Figure 1

Corrosion behavior of pure Ti under continuous NaCl solution spraying at 600 °C

The corrosion behavior of pure Ti under continuous NaCl solution spraying at 600 °C, compared with that under solid NaCl deposit film in H2O + O2 environment, has been studied by mass gain curves, detailed microstructural investigation and phase-stability diagram. The results indicate that the oxide scale consists of three repeated multi-layered subscales composed of Na2TiO3 and TiO2. Continuous NaCl increases the volatilization of TiCl4 towards oxide/atmosphere interface as well as introduces pores and cracks. Pores and cracks allow the oxidizing atmosphere to enter and rapidly spread and resulting in a repeat multi-layered oxide scale. Relatively dense repeat TiO2 delayed active oxidation process, which will decrease the corrosion rate of the pure Ti under NaCl spraying.

High-temperature corrosion behaviour of Pt-modified aluminide coating with solid NaCl deposit in O2 + 10 vol% H2O and the influence of pre-oxidation treatment

The electroplating and subsequent above-pack aluminisation were used to prepare a single-phase (Ni,Pt)Al coating on the second generation Ni-based single crystal superalloy. Corrosion behaviour of the (Ni,Pt)Al coating with and without pre-oxidation have been evaluated at1000 °C under simulated marine-environment. The results indicated that the pre-oxidised coating exhibited improved corrosion resistance compared with the one without pre-oxidation, due to the formation of stable and exclusive α-Al2O3 layer. The synergistic effect of NaCl and water vapour plus oxygen on the corrosion mechanism of (Ni,Pt)Al coating was intensively discussed.

Effect of pre-hot salt corrosion on hot salt corrosion fatigue behavior of the TC11 titanium alloy at 500 °C

Pre-hot salt corrosion (PHSC) tests is the samples with 0.1, 0.5, 1 and 4 mg/cm2 salt coating are corroded at 500 °C for 100 h. The hot salt corrosion fatigue (HSCF) tests were conducted on PHSC specimens at a stress ratio, a maximum stress amplitudes and temperature of −1, 450 MPa and 500 °C, respectively. The effect of PHSC on HSCF behavior of TC11 alloy at 500 °C was studied by deposition of solid NaCl. The HSCF sensitivity of the TC11 alloy at 500 °C was further increased by PHSC, and increased gradually with the increase in solid NaCl content. When the salt content exceeded 1 mg/cm2, the HSCF life was reduced by more than 99% compared with the samples without salt coating. The mechanism of HSCF was that the local stress concentration of the corrosion pits accelerated the initiation of fatigue cracks, hydrogen and the hydride phase promoted fatigue crack propagation. The PHSC process promoted the formation of corrosion pits, and accelerated the infiltration of hydrogen into the matrix and hydride formation, so the fatigue resistance of pre hot salt corrosion samples was reduced further. A greater NaCl deposition resulted in more severe surface corrosion damage of the titanium alloy, a stronger coupling of corrosion factors and alternating load in the HSCF process, and a greater reduction in fatigue resistance.

An amorphous SiAlN barrier coating against NaCl attack in humid air at elevated temperature

Amorphous magnetron sputtered SiAlN films have been designed to prevent NaCl attack of Ti alloy substrates in high temperature humid air environments. Uncoated Ti alloys suffer severe degradation after exposure to NaCl deposits in humid air at 700 °C for 100 h, whereas SiAlN coating forms protective scale mainly consisting of sodium silicate in identical conditions. Amorphous sodium silicate exhibits fast Na+ diffusion rate and extremely slow O2- diffusion rate, but degradation of SiAlN takes place in presence of both O2- and Na+ species. Sodium silicate scale provides good protection for SiAlN due to slow diffusion of O2- through sodium silicate.

Influence of solid particles deposition on the initial atmospheric corrosion of 7B04 aluminum alloy

The influence of the deposition of three different particles (NaCl, C and SiO2) on the initial atmospheric corrosion of 7B04 aluminum alloy was investigated via laboratory exposure testing, environmental scanning electron microscope (E-SEM), energy dispersive X-ray spectroscopy (EDS), and scanning Kelvin probe (SKP). The results showed that the deposition of NaCl had a significant acceleration effect on the initial corrosion of 7B04 aluminum alloy and resulted in the occurrence of localized corrosion on sample surface. Because of its capillary condensation effect, SiO2 could absorb the vapor in humid environment to form a local water-rich area around the particles which could promote the corrosion of 7B04 aluminum alloy. C had basically no effect on the corrosion of 7B04 aluminum alloy.

Selective Allowance of Precipitation from Oversaturated Solution Using Surface Structures.

Precipitation is a well-known phenomenon commonly observed in salt ponds. However, it causes pipe clogging in industrial sites, which can be resolved by controlling the direction of precipitation. Herein, we propose a method to control the precipitation direction by changing the structures and properties of the solid surface. Bare, nanostructured, microstructured, and micro/nanostructured surfaces were immersed in the same saturated aqueous NaCl solution, and the heights at which precipitation occurred in the different specimens were compared. On bare and nanostructured surfaces, NaCl deposits as a flat layer on the surface, while on micro and micro/nanostructured surfaces, it forms a thick deposit in a direction perpendicular to the surface. When the same experiment was conducted on surfaces made by patterning different structural surfaces, the precipitates did not spread on the surface with microscale structures. We believe that this novel approach may prove useful in solving the problems caused by precipitation.

Salty water and salty leaf litter alters riparian detrital processes: Evidence from sodium-addition laboratory mesocosm experiments

Terrestrial and freshwater secondary salinization is a global phenomenon arising partially from anthropogenic activities. How low-level direct (e.g., sodium exposure through irrigation runoff) or indirect (e.g., sodium exposure through sodium-enriched leaves as riparian plants uptake sodium that via senescence enters detrital systems) impacts detrital processes in riparia have received little attention. Based on the sodium ecosystem respiration hypothesis, we predicted low-level salinization of an inland mesic riparia would result in increased detrital processing and increased leachate dissolved organic carbon (DOC) and conductivity. Two riparian soil mesocosm experiments tested how low-level salinization affects leachate chemistry and conductivity and riparian decomposition rates and detritivore community structure: 1) direct low-level NaCl deposition in water (weekly additions of 300 ml of 0.05% NaCl or just H2O (controls)), and 2) indirect low-level NaCl deposition through Na-enriched artificial litter (0.05% NaCl or just H2O (controls)). After three months, leachate Na+ concentrations were 12-fold and 1.5-fold higher in Na-addition than control mesocosms for direct and indirect Na-addition experiments, respectively. Contrary to predictions, decomposition rate was 1.3-fold lower in indirect Na-addition than control mesocosms but invertebrate communities were similar. Decomposition rate did not differ in direct Na-addition experiments, and although invertebrate abundance was lower, diversity was 1.4-fold higher in Na-addition than control mesocosms. Leachate DOC did not differ between Na-addition and control mesocosms for either direct or indirect Na-addition experiments. This study adds to the growing evidence that even low-level Na addition can stress inland mesic terrestrial systems and demonstrates that even Na-enriched detritus alone can induce salt-stress in riparian soil systems. These results suggest that even low-level salinization of riparia can impact riparian ecosystem function and leachate chemistry through direct exposure and indirectly through Na-enriched detritus, a previously overlooked pathway.

Effects of salts and its mixing ratio on the corrosion behavior of 316 stainless steel exposed to a simulated salt-lake atmospheric environment

The effect of mixed salts and mixing ratio on the corrosion behavior of 316 stainless steel exposed to a simulated salt-lake atmosphere has been firstly investigated. 316 stainless steel was mainly analyzed by the evolution of surface morphologies, composition of corrosion products, statistics of pits depth and width and electrochemical measurements. The results indicated a layered double hydroxides (LDH) was detected in the corrosion products formed on 316 stainless steel surface under different salt deposition conditions, except under single NaCl deposition condition. When the mole fraction of NaCl was 0.75 in mixed MgCl2 – NaCl salts, the corrosion rate of 316 stainless steel was the fastest. The width of the pits formed on the surface of 316 stainless steel under mixed MgCl2 - NaCl salts deposition conditions was smaller than that under single MgCl2 deposition condition. The differences in corrosion rate and pit width size of 316 stainless steel under mixed MgCl2 - NaCl salts deposition conditions and single MgCl2 deposition condition were related to diffusion barrier provided by the neighboring NaCl crystals precipitated in thin liquid film during the humidification process and dehydration process.

Corrosion mechanism of Ti2AlC MAX phase coatings under the synergistic effects of water vapor and solid NaCl at 600 °C

The corrosion behavior of Ti2AlC MAX phase coatings coated on 1Cr11Ni2W2MoV substrates in NaCl deposit in water vapor at 600 °C has been fully investigated. The results demonstrated that the substrates underwent serious corrosion, but the coatings performed better. The mass gain per unit area of coatings was less than 1/6 of substrates, because of the formed compact and uniform corrosion scale. Such dense corrosion scale was composed of NaxTiyOz fine grains with the size of 11 ± 0.4 nm and amorphous Al2O3 phases which self-healed the generated defects during corrosion, benefiting from the novel layered structure of MAX phase.

Protection of 304 stainless steel by nano-modified silicone coating in cyclically alternate corrosion environment

A nano-modified silicone-based composite coating was developed to protect 304 stainless steel under a cyclically alternate corrosion condition. Each cycle contained alternate exposure in a neutral salt spray test chamber at 35 °C and in a muffle furnace at 400 °C. The results showed that the corrosion of 304SS was serious. The nano-modified silicone coating, which is composed of a continuous amorphous SiO2 matrix, dispersive Al, Al2O3, TiO2 and ZrO2 particles and discrete voids after the cyclically alternate corrosion, are inert at 400 OC in the environment containing NaCl deposit and oxygen and significantly improved the corrosion resistance of the 304SS.

Temperature and NaCl deposition dependent corrosion of SAC305 solder alloy in simulated marine atmosphere

The stable operation of electronic devices in marine atmospheric environment is affected by the corrosion deterioration of solder joints, and the effects by atmosphere temperature and chloride deposition are critical. In this work, NaCl deposition and temperature dependent corrosion of Pb-free SAC305 solder in simulated marine atmosphere has been investigated. The results indicate that higher NaCl deposition prolongs the surface wetting time and leads to the final thicker saturated electrolyte film for further corrosion. Higher temperature accelerates the evaporation and contributes to the final thinner saturated NaCl electrolyte film. Besides, the corrosion control process varies under the initially covered thicker NaCl electrolyte layer and under the final saturated much thinner NaCl electrolyte film as the evaporation proceeds. Moreover, the ready oxygen availability through the final thinner saturated NaCl electrolyte film facilitates the formation of corrosion product layer mainly of electrochemically stable SnO2, but higher temperature leads to the final corrosion product layer with smaller crystal size and large cracks. The findings clearly demonstrate the effects of NaCl deposition and temperature on corrosion evolution of SAC305 solder joints and are critical to the daily maintenance of electronic devices for longer service life in marine atmosphere.

Effects of pre-oxidation on the corrosion behavior of pure Ti under coexistence of solid NaCl deposit and humid oxygen at 600\xa0\xb0C: the diffusion of chlorine

The effect of pre-oxidation on the corrosion behavior of pure Ti covered with a solid NaCl deposit in the humid O2 flow at 600 °C is studied. The oxide scale, formed by pre-oxidation, protects the substrate from the NaCl induced corrosion during the initial stage. However, the corrosion of the pre-oxidized sample is severely accelerated by solid NaCl after an incubation period. The chlorine, generated from the decomposition of solid NaCl, diffuses into the oxide/substrate interface as ions during the incubation period, which was observed by ToF–SIMS. The chlorine at the oxide/substrate interface induces the fast corrosion after the incubation period although the pre-oxidation scale is complete and compact.

Effects of the Different Solid Deposits on the Corrosion Behavior of Pure Fe in Water Vapor at 500°C.

A comprehensive corrosion investigation of pure Fe in an environment of solid sodium salt deposit (i.e., NaCl or Na2SO4) with mixtures of H2O and O2 at 500°C was conducted by mass gain measurement, X-ray diffraction (XRD), scanning electron microscope (SEM), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results showed that corrosion rates were accelerated with solid NaCl or Na2SO4 deposit due to their reaction with the formed protective scale of Fe2O3 and subsequently resulted in its breakdown. The corrosion rate of pure Fe with solid NaCl is higher than that with solid Na2SO4 because of the lower activation energy (Ea) for chemical reaction of Fe in solid NaCl+H2O+O2 (i.e., 140.5 kJ/mol) than that in solid Na2SO4+H2O+O2 (i.e., 200.9 kJ/mol). Notably, the electrochemical corrosion rate of pure Fe with solid NaCl deposit, 1.16 × 10−4 A/cm2, was a little lower than that with solid Na2SO4 deposit.

Degradation mechanism of Ti-6Al-2Sn-4Zr-2Mo-Si alloy exposed to solid NaCl deposit at high temperature

This study focuses on the corrosion behaviour of Ti-6Al-2Sn-4Zr-2Mo-Si alloy in presence of NaCl deposit in air at 560 °C. The active oxidation mechanism at the origin of the corrosion phenomenon enhancement in presence of solid NaCl is thought to be connected to the formation of both external and internal thick oxidation areas. Thermodynamic calculations allowed showing the role played by the different alloying elements in the formation of the external oxide and detailed TEM characterisations brought new insights regarding the nature and origin of the internal oxidation area.

Crystallization-Driven Flows within Evaporating Aqueous Saline Droplets.

Using micro-PIV (particle image velocimetry), we observe for the first time, the direct correlation between crystallization and hydrodynamics in evaporating microliter saline (1 M NaCl) sessile drops. The relationship is demonstrated by a remarkable jet of liquid along the base of the drops, induced by, and directed at the point of nucleation and subsequent crystal growth. Prior to nucleation, the flow is more uniformly outward with the magnitude of the velocity decreasing with time. From calculations and the flow measurements in the two observed stages of evaporation (prior to nucleation and during crystallization), this jet can be explained on the basis of competition between solutal Marangoni convection and mass conservation flow. The jet of fluid leads to vortices on either side of the crystal in which the salt concentration is reduced, providing a potential explanation as to why NaCl deposits as a sequence of discrete crystals rather than as a continuous ring for such drops.

Enhanced oxidation and corrosion inhibition of 1Cr11Ni2W2MoV stainless steel by nano-modified silicone-based composite coatings at 600°C

Silicone-based composite coatings modified by ZrO2 nanoparticles were applied on the 1Cr11Ni2W2MoV steel. Their oxidation and corrosion performances were evaluated in air and an environment containing solid NaCl and water vapor at 600 °C, respectively. The coating with 20 wt.% ZrO2 exhibited better oxidation resistance than those with 10 and 30 wt.% ZrO2, while the coating with 20 or 30 wt.% ZrO2 exhibited better resistance against the corrosion induced by water vapor and solid NaCl deposits than those with 10 wt.% ZrO2.

Corrosion Behavior of 304 Stainless Steel Exposed to a Simulated Salt Lake Atmosphere

The corrosion behavior of stainless steel exposed to a simulated salt lake atmosphere has been investigated by analyzing the evolution of surface morphologies and corrosion products, the initiation and development of pits, and the electrochemical characteristics. The results indicated that (Mg6Fe2(OH)16(CO3)(H2O)4.5)0.25, a layered double hydroxide, has been detected for the first time in the corrosion products formed on stainless steel exposed to a simulated salt lake atmosphere. The specimens exposed to MgCl2 deposit conditions were corroded more severely than those exposed to NaCl deposit conditions, which was attributed to the differences in the deliquescence relative humidity and efflorescence relative humidity values of MgCl2 and NaCl. In addition, a special corrosion morphology consisting of a concentric circle of yellowish material was observed on the specimens exposed to MgCl2 deposit conditions, which was attributed to the formation of Mg(OH)2, inhibiting the diffusion and migration of OH− ions to the anode region. The maximum pit depth followed a power function with respect to corrosion time. The corrosion mechanism of stainless steel exposed to a simulated salt lake atmosphere is also discussed.

Effect of streaming water vapor on the corrosion behavior of Ti60 alloy under a solid NaCl deposit in water vapor at 600 °C

The corrosion behavior of Ti60 alloy coated with solid NaCl layer in dry O2 and humid O2 (30.8 vol.% H2O) environments at 600 °C have been investigated. The isotopic tracing of 18O showed involvement of H2O in both the outer corrosion layer (OCL) and the inner corrosion layer (ICL). Theoretical calculations revealed that H2O provided 14% and 21% of the oxygen required for the formation of the outer and inner corrosion layers, respectively. Detailed analysis of corrosion products revealed that H2O enhanced the reaction of solid NaCl and TiO2 to form Na4Ti5O12 and promoted the crystallinity of corrosion products.