Salt Spray Environment Research Articles

Genome engineering of materials based on Ce doping, high-performance electromagnetic wave absorber for marine environment

Traditional microwave absorbing materials (MAM) are difficult to meet the current increasingly complex electromagnetic environment, MAM began to functionally integrated development to meet the needs of diversified applications. For the high humidity and high salt spray environment of the ocean, the development of electromagnetic absorber integrating microwave absorption (MA) and corrosion protection functions is imminent. In this work, high-quality genes were screened through materials genome engineering, and in-situ doping strategies of Ce gene were designed to synergistically enhance MA properties using composition modulation and structure modulation, the effective absorption bandwidth (EAB) of composite material WC@FCC1 can reach 5.62 GHz at an ultra-thin thickness of 1.66 mm. Thanks to the unique 4f orbital mechanism of Ce element, CeO2 is endowed with excellent redox property, forming an oxide protective film on the surface, which prevents the entry of external corrosive media. The excellent corrosion protection performance of the composite material has been verified through electrochemical testing and molecular dynamics simulation. This work provides new design ideas for high-performance MAM, as well as new strategies and insights for functionally integrated electromagnetic absorber.

Enhanced high-temperature corrosion resistance of Cr-modified phosphate/aluminum powder composite coatings: Mechanisms and thermodynamic insights

Phosphate composite coatings are regarded as one of the tangible solutions for surface protection in salt spray environments, benefiting from their cost-effectiveness and prominent structure stability upon high-temperature exposure. However, rapid curing of these coatings often leads to crack formation, and the underlying corrosion mechanisms in service conditions remain insufficiently understood, limiting their practical applications. In this study, we developed chromium-incorporated phosphate/aluminum powder composite (Cr-P/Al) coatings and evaluated their corrosion resistance under alternating conditions of salt spray corrosion and oxidation at 450 °C. By integrating experimental results, ab initio calculations, and thermodynamic analysis, we demonstrate that the incorporation of Cr significantly enhances the performance of the P/Al coatings. The structural evolution was first revealed that Cr’s modification reduced tensile stress and prevented cracks in the coating. A mixed layer of amorphous oxides and phosphates forms on the surface of the Al powder, providing robust binding strength. A novel corrosion mechanism was identified that Cl2 and volatile chlorides facilitated the removal of Cl-. This process is more ineffective with Cr-P/Al coating, as amorphous Cr oxide has low reactivity at a high log[p(Cl2)] and low log[p(O2)] compared with amorphous Mg and Fe oxide, thereby enhancing the corrosion resistance of the coating. These coating densification methods and corrosion protection mechanisms provide a critical foundation for the future application of phosphate composite coatings.

Frictional properties and environmental adaptability of Ti-MoS2/WC multilayer films

Magnetron-sputtered molybdenum disulfide films are extensively utilized as solid lubricating coatings in space applications as a result of their low friction coefficient and minimal contamination. However, MoS2-based films are sensitive to hygrothermal and oxidation environment, and are easily oxidized to form MoO3, which results in high friction and wear of the films, significantly reducing their operational lifespan. Especially when the spacecraft adopts the launching mode of coastal launch or ocean platform, the performance deterioration caused by oxidation of MoS2 films during transportation, storage and launch is more serious. Therefore, to enhance the frictional performance and oxidation resistance of the films in humid and salt spray environments, the Ti-MoS2/WC multilayer films with preferred (002) crystal plane orientation were prepared, achieving a friction coefficient of 0.009 in a vacuum environment and a wear rate of 1.1×10-7 mm3/N∗m. In particular, the film can maintain this extremely low coefficient of friction even after exposure to moisture or salt spray. These findings demonstrate that the dual doping of Ti and WC and the design of multilayer structures enable MoS2 films to achieve outstanding frictional performance and oxidation resistance. This is crucial for designing MoS2 films with excellent environmental adaptability.

Interface needle structure induced high-performance aluminum alloy/PPS hybrids

Direct joining molding of metals and polymers has received increasing attention in the field of lightweight fabrication. The aluminum alloy (Al) surface was modified by secondary anodizing and a special needle-like structure was formed on the Al surface. Then, the glass fiber-filling polyphenylene sulfide (PPS) was directly joined with Al by the hot pressing technique. The relationship between the interfacial structure and mechanical properties of Al/PPS hybrids was systematically investigated and discussed. The results showed that the generation of needle-like structures could improve the surface roughness and wettability, thus effectively improving the mechanical interlocking ability of the interface and forming the Al-O-C chemical bond with PPS. The maximum tensile strength of Al/PPS hybrids was 28.34 MPa, and their impact toughness (ak) reached 9.69 J/cm2. Even though the hybrids were exposed to a salt spray environment or 200 °C, the strength could still reach 25 MPa. This study has prepared a high-performance metal/plastic hybrid by secondary anodizing method, which can be applied in harsh environments.

Study on corrosion resistance of arc sprayed Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings in salt spray environment

AbstractTo study the corrosion behavior of Zn–Al pseudo alloy coatings with different Al contents, Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings were prepared by the wire arc spraying technique using Zn and Al wires with different diameters. This study investigated the microstructure, electrochemical corrosion behavior, and corrosion morphology and products of the as‐sprayed coatings after the salt spray test in 5 wt% NaCl solution. The results exhibited that the Zn–Al pseudo alloy coatings with higher Al content form denser corrosion products (Zn5(OH)8Cl2·H2O and Zn–Al layered double hydroxide) with stronger self‐shielding effect against corrosive media, thus provide better long‐term corrosion protection. Besides, electrochemical reactions are controlled by mass transfer until corrosion for 24 h, and then by a combination of mass transfer and diffusion for 96 h. Overall, it can be concluded that the Zn–37Al pseudo alloy coating in this study shows great potential to protect steel substrates from corrosion.

Needle-like structure grafted with chemical bond induces high-performance polyformaldehyde-aluminum alloy hybrids

The high-performance polymer-metal hybrids (PMH) have received widespread attention in the automotive field. In this study, needle-like structures were formed on the aluminum alloy (Al) surface by secondary anodizing. Based on that, the Al surface was further silanized. The surface-treated Al was then connected to polyformaldehyde (POM) by ultrasonic-assisted hot pressing molding to fabricate POM-Al hybrids. The source of the bonding strength of POM-Al hybrids has been systematically explained. When the POM embedding rate reached 91.32 % and the interface coexisted with Al-O-Si and Al-O-C bonds, the bonding strength reached 46.89 MPa, representing a 129 % increase against primary anodization. Furthermore, the bonding strength was able to exceed 40 MPa in a salt spray environment and high-temperature conditions. In general, these results can facilitate the development and application of PMH products in practical engineering.

Study on the influence of Salt spray environment on impact fatigue of Gun parts

Study on the influence of Salt spray environment on impact fatigue of Gun parts

Experimental investigation on seismic performance of CHS T-joints in salt spray environment

This paper aims to investigate the seismic performances of circular hollow section (CHS) T-joints with different regions of corrosion damage. A total of seven CHS T-joint specimens with various corrosion degrees were applied to conduct the quasi-static tests of brace axial cyclic loading, and the effects of corrosion damage on the hysteresis behavior and failure mode were discussed. Experimental results indicated the brace corrosion only had a slight influence on the seismic performance of CHS joints, while the corrosion difference on two sides of the brace might cause an additional bending moment and damage accumulation to accelerate the plastic collapse of the connection zone. Compared with the corrosion on the brace, the resistance of CHS joints was more susceptible to the corrosion located in the chord wall, resulting in the axial cyclic carrying capacity and stiffness of CHS joints significantly decreasing with the increase of chord corrosion level. However, the increasing corrosion on the chord would affect the final fracture behavior and fracture position, so the total energy dissipation and deformation of CHS joints presented a complicated and nonlinear degradation trend. In addition, corrosion damage simultaneously had an impact on reducing the bending capacity of the chord, and this phenomenon not only caused the differences between the degradation rates of axial tensile and compressive strength of CHS joints but also affected the failure mechanism and local deformation of CHS joints under the brace axial cyclic loading.

Effects of microstructure on the corrosion behavior of pearlitic rail steel under simulated salt fog conditions

In this paper, the corrosion resistance and mechanisms of rail specimens with different lamella spacings in a salt spray environment were evaluated and investigated. This investigation was achieved by controlling different cooling rates of pearlitic bodies through heat treatment to obtain various lamella spacings. The results indicated that the corrosion resistance of all the specimens decreased during the salt spray test. The specimens with slow cooling rates (resulting in large pearlitic sheet layer spacings) had poorer corrosion resistance than those with fast cooling rates. Specimens obtained with both fast and slow cooling rates (air cooling at a 0.01 °C/s cooling rate) displayed similar corrosion patterns. However, the corrosion stability of the specimen obtained at a cooling rate of 0.03 °C/s fluctuated considerably after 144 h of salt spray corrosion. This fluctuation was attributed to the transformations of corrosion products within the rust layer. The structural stability of the rust layer was related to the defects present in the material. Large defects increase the instability of the rust layer, thereby increasing the susceptibility to corrosion in a salt spray environment.

Structure and properties of the hot pressing molded anodized aluminum alloy/polyformaldehyde hybrids

The metal-plastic hybrid is one of the important solutions for lightweight and high-strength composite. The anodized aluminum alloy（AAA）/polyformaldehyde（POM） hybrids with excellent mechanical properties were processed by the hot pressing technology. The surface of the aluminum alloy plate was firstly pretreated with phosphoric acid and oxalic acid anodizing, resulting in a large number of micro-nano scale pores on the surface. These pores were well embedded with plastic melt during hot pressing to form micro-nano mechanical interlocking structures and the Al–O–C chemical bond at the interface is generated, thus ensuring good bonding strength at the metal and plastic interface. The maximum tensile-shear strength of the metal-plastic hybrid was 30.65 MPa, meanwhile, the metal-plastic interface failure presented mainly a mixed failure mode, including resin removal from the metal surface and plastic tearing from the plastic surface. At the same time, the salt spray test, thermal shock test, and variable temperature test were adopted to investigate the application performance of the metal-plastic hybrid. The Al/POM hybrids were able to maintain their mechanical strength above 20 MPa for 28 days in a salt spray environment, 14 times in a thermal shock cycle, and at high temperatures. The high mechanical strength of hybrid has good potential for automotive applications.

Non-destructive degradation assessment of GFRP beams subjected to hygrothermal ageing

This work used free vibration tests based on impulse excitation technique and experimental modal analysis using an impact hammer and an accelerometer to assess the local and global effects of the hygrothermal ageing of GFRP specimens exposed to salt-spray environment at 35°C and 60°C over a period of 136 days. Through the change in elastic properties, fifteen natural frequencies and damping ratios, the effects of degradation are associated with reductions in elastic properties and natural frequencies and an increase in damping ratios. In turn, the increase in elastic properties and natural frequencies – associated with a reduction in damping ratios – is mainly attributed to the post-curing effect.

Experimental Investigation for Proton Exchange Membrane Fuel Cells in Marine Salt Spray Environment.

In the maritime setting, Proton Exchange Membrane Fuel Cells (PEMFCs) are subjected to salt spray, posing a risk of contaminating internal components and leading to irreversible degradation in the performance of the PEMFCs. Thus, it is crucial to assess the impact of sodium chloride contamination on PEMFC operation. To address challenges related to prolonged cycle times, high costs, and intricate sample preparation in sodium chloride contamination experiments for PEMFCs, this Article replicates the marine atmospheric conditions using a standard salt spray experimental chamber. The liquid nitrogen fracture method is employed for cost-effective and efficient preparation of experimental samples. The meteorological environment with varying salt content in the salt spray is achieved through precise control of sodium chloride concentration. The Article systematically presents the salt spray experimental method for the membrane electrode assembly (MEA) of PEMFCs. A dedicated salt spray experimental rig was constructed to validate this method for the MEA of PEMFCs. The results indicate that the salt spray experimental method for the MEA of PEMFCs can effectively explore internal component contamination and is well-suited for analyzing the physicochemical effects of NaCl on MEA components, along with their microscopic characterization under salt spray conditions.

Design and realization of versatile durable fluorine-free anti-corrosive coating with robust superhydrophobicity

Bio-inspired superhydrophobic coatings are of increasing interest in marine corrosion protection due to their superior barrier and shielding effects. However, some difficult problems like weak mechanical strength, the use of costly and toxic reagents, and intricate preparation processes have long hindered the practical application of the superhydrophobic coatings. Herein, a durable, self-cleaning and anti-corrosion superhydrophobic coating based on epoxy resin matrix was successfully fabricated, avoiding the use of fluorine materials. The prepared coating possessed excellent superhydrophobicity and was applicable to a variety of substrates, which was ascribed to the effect of modified kaolin particles on lowering surface energy. Through SEM and LSCM, the superhydrophobic coatings manifested the morphology feature of "hills+mountain", which could store air to reduce solid-liquid contact. The prepared coating had been proven to have greater impedance modulus and charge transfer resistance by EIS test, and displayed outstanding durability in salt spray environment compared with pure epoxy coating. In addition, the sandpaper abrasion, standard cross-cut tape and self-cleaning tests indicated that the superhydrophobic coatings satisfied robust mechanical stability and excellent resistance to contaminants, laying the foundation for the application of superhydrophobic coating in practical environment.

Strength Degradation Mechanism of CFRP and Aluminium Alloy Hybrid Bonded-Riveted Joints Under Salt Spray Environment

Strength Degradation Mechanism of CFRP and Aluminium Alloy Hybrid Bonded-Riveted Joints Under Salt Spray Environment

Corrosion behavior and cellular automata simulation of carbon steel in salt-spray environment

Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to discuss the corrosion loss and morphology of the pit and rust layer of carbon steel. It was found that the corrosion process is largely influenced by the cyclic shedding of surface corrosion products, in addition to being controlled by the mechanism of oxide film shedding and pit evolution. A corrosion mechanism (the mechanism of rust layer shedding) is proposed. As a result, in this paper, the corrosion process of the test steel is simulated by the cellular automata. It was set up that the mechanism of oxide film shedding, the mechanism of pit evolution, and the mechanism of rust layer shedding in Cellular Automata Simulation. The optimal time ratio and simulation parameters were found, and a predictable cellular automata corrosion simulation model was built, providing a solution for carbon steel’s service life prediction.

Corrosion Behavior of Homogenized and Extruded 1100 Aluminum Alloy in Acidic Salt Spray.

The 1100 aluminum alloy has been widely used in many industrial fields due to its high specific strength, fracture toughness, excellent thermal conductivity, and corrosion resistance. In this study, the corrosion behavior of the homogenized and hot-extruded 1100 aluminum alloy in acid salt spray environment for different time was studied. The microstructure of the 1100 aluminum alloy before and after corrosion was characterized by an optical microscope (OM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and a laser scanning confocal microscope (LSCM). The difference in corrosion resistance between the homogenized and extruded 1100 aluminum alloy was analyzed via the electrochemical method. The results indicate that after hot extrusion at 400 °C, the microstructure of the 1100 aluminum alloy changes from an equiaxed crystal structure with (111) preferentially distributed in a fibrous structure with (220) preferentially distributed. There was no obvious dynamic recrystallization occurring during extrusion, and the second-phase particles containing Al-Fe-Si were coarse and unevenly distributed. With the increase in corrosion time, corrosion pits appeared on the surface of the 1100 aluminum alloy, and a corrosion product layer was formed on the surface of the homogenized 1100 aluminum alloy, which reduced the corrosion rate. After 96 h of corrosion, the CPR of the extruded samples was 0.619 mm/a, and that of the homogenized samples was 0.442 mm/a. The corrosion resistance of the extruded 1100 aluminum alloy was affected by the microstructure and the second phase, and no protective layer of corrosion products was formed on the surface, resulting in a faster corrosion rate and deeper corrosion pits.

Exploring the electrochemical and mechanical properties of lithium-ion batteries in salt spray environments

With the pressing need to expedite the transition toward a greener marine industry, energy-efficient and eco-friendly lithium-ion batteries (LIBs) are increasingly favored. However, compared to land applications, marine environments pose unique challenges to the utilization of LIBs, thereby necessitating targeted safety measures. In this study, prismatic LIBs (PLIBs) are subjected to standard salt spray tests to emulate marine environments, and the resultant morphological changes and external voltage response of the batteries under the corrosion behavior are analyzed. Subsequently, the impacts of the salt spray environment on the electrochemical performance of PLIBs are assessed through a range of characterization techniques including scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and charge-discharge test. Finally, quasi-static ball indentation tests are carried out on the corroded batteries to study the behaviors under mechanical abusive loading scenarios. Results reveal that the most prominent effect of the salt spray environment on the batteries is the occurrence of swelling, attributable to the imperfect sealing of the battery tabs. This study represents an innovative exploration of the viability of LIBs in the marine environments, providing fundamental theoretical guidance for early detection of battery corrosion and collision risks, as well as facilitating protective design considerations.

Investigation on the Corrosion Resistance of 3003 Aluminum Alloy in Acidic Salt Spray under Different Processing States

3003 aluminum alloy exhibits commendable corrosion resistance, ease of processing, and good formability, rendering it extensively utilized across many industrial sectors. In this study, the corrosion behavior of 3003 aluminum alloy in a homogenized state and after hot extrusion deformation in an acidic salt spray environment for different times was studied. The microstructure of the 3003 aluminum alloy in the homogenized state and after hot extrusion was characterized using scanning electron microscopy (SEM), optical microscope (OM), laser scanning confocal microscope (LSCM) etc., while electrochemical methods were employed to study the difference in corrosion resistance between these two states. The results show that corrosion pits on the surface of the homogenized 3003 aluminum alloy increase with time, and corrosion extends along the second phase arrangement, while the hot extruded 3003 aluminum alloy mainly exhibits corrosion pit extension. The grain size of the homogenized 3003 aluminum alloy is larger than that of the hot extruded state, and the second phase is distributed in a reticular pattern. Hot extrusion deformation ensures not only a uniform distribution of the second phase in the 3003 aluminum alloy but also a reduced grain size, an increased grain boundary density, a heightened electrochemical activity in acidic environments, and an augmented pitting density. Compared with the homogenized 3003 aluminum alloy, the pitting density, maximum pitting depth, and weight loss of the hot extruded state are increased.

Corrosion Behavior and Mechanism of WC-12Co Coating in Salt Spray Environment

Corrosion Behavior and Mechanism of WC-12Co Coating in Salt Spray Environment

Mechanism of corrosion behavior between Pb-rich phase and Cu-rich structure of high Sn–Pb bronze alloy in neutral salt spray environment

The corrosion behavior and corrosion mechanism of the Pb-rich phase and Cu-rich structure of the Sn–Pb bronze alloy in a high-chloride and high-humidity environment were studied. The phase composition of the bronze alloy was analyzed by observing the metallographic and EPMA element distribution, the potential of the microstructure was characterized by SKPFM. The corrosion products and morphology results after electrochemical and neutral salt spray tests were analyzed. The results showed that the matrix structure of bronze material was composed of Pb-rich phase and Cu-rich structure (α(I) phase and (δ+α(II)) eutectoid). During the corrosion process, the rich Pb phase preferentially corroded as the anode and diffused towards the surroundings, while the rich Cu structure served as the cathode. In the rich-Cu structure, compared with δ, the α phase was used as the anode. The corrosion products on the alloy surface mainly included Cu2O, PbCO3, and Cu2(OH)3Cl. As the corrosion gradually deepened along the depth of α phase, the galvanic couple effect between α phase and δ phase and the “oxygen concentration cell” effect gradually increased.