Salt Fog Environment Research Articles

Study on powdering properties of silicone rubber insulating material in a coastal area

Abstract Silicone rubber insulation materials are widely used in energy systems. The powdering of silicone rubber sheds is a newly discovered aging phenomenon in recent years, and there is no specific research. In this paper, the powder composition of the composite insulators in coastal areas was studied, and the powdering process of silicone rubber under a high humidity environment of salt fog was repeated in the laboratory. The results show that the powders can be divided into two types according to particle shape, element composition, and molecule groups: the inorganic filler and its dehydrated product and the small molecule siloxane after polymer aging fracture. The particle size of Type I of powder is 3∼8μm, and the particle size of Type II of small molecule siloxane is 0.3∼1.1μm. The surface hydrophobicity of the powdered sample in a salt-fog environment will deteriorate, and the static contact angle will decrease. However, the hydrophobicity will gradually recover after leaving the harsh environment. Powdering of composite insulator silicone rubber in coastal areas is a complex physical and chemical process caused by the combined action of electricity, heat, and moisture. During this, polymer molecular chains break, and fillers gradually precipitate, forming powders.

Assessing charge accumulation and flashover phenomena on silicone rubber surface exposed to salt-containing droplets under direct current voltage

In damp and salt-fog environments, silicone rubber composite insulators are prone to forming dispersed droplets that absorb airborne salt nuclei, leading to charge accumulation and potentially causing flashovers that threaten transmission line stability. Regrettably, these concerns have not yet received sufficient attention from relevant researchers. This study examines the surface charge accumulation and flashover characteristics of silicone rubber insulators with droplets of varying electrical conductivity. The droplets can fix charges, as the conductivity of droplets on insulator surfaces increases, the migration rate of surface charges accelerates, causing distortion of the electric field and a significant increase the area of high-density charge regions on the sample surface. Compared with dry surfaces, increasing the equivalent salt density of salt-containing droplets attached to the surface from mild to severe (with conductivity increasing from 800 μS/cm to 2800 μS/cm) leads to a 25 %-40 % increase in the average surface charge density. After adsorbing charges, the salt droplets shorten the discharge development path, making it easier to trigger interface discharge. Compared with dry surfaces, the average flashover voltage of the salt droplets is reduced by at least 30 %. This study offers valuable analysis on charge accumulation and flashover for silicone rubber insulators in salt-fog environments.

Calculation of Characteristic Point Parameters for Restoring Model of Corroded Short-Pier RC Shear Walls

Based on the quasi-static tests of 12 corroded RC (reinforced concrete) shear walls, it was found that reinforcement corrosion has a great influence on the skeleton curve of RC shear walls. With an increase in the degree of corrosion, the bearing capacity of specimens decreases, and the deformation capacity worsens. Increasing the diameter of longitudinal reinforcements can significantly improve the bearing capacity of corroded RC shear walls, while the deformation capacity of corroded specimens can be improved by increasing the lateral distributed reinforcement or the transverse reinforcement in the embedded column. In order to accurately evaluate the seismic performance of corroded RC shear walls, we considered descent segments of four broken-line models to estimate the skeleton curve. After considering the influence of corrosion on the parameters of the characteristic point for the skeleton curve, the calculation formulas of the characteristic point parameters of the skeleton curve for the corroded RC shear wall were determined based on the test data fitting. It was proven that the formula for the characteristic point parameters for the skeleton curve of corroded RC shear walls has good applicability. This study lays a theoretical foundation for the seismic performance evaluation of an RC shear wall structure in a salt fog environment. It provides a theoretical basis for further improving the life-cycle seismic capacity evaluation system for RC structures.

Tribo-electrical properties of copper matrix composites in salt-fog environment

To enhance the reliability of floating offshore wind platforms exposed to salt-fog environment, a new material, CNTs-MoS2/Cu, was developed for slip rings. Tribo-electrical properties of composites in salt-fog environment were explored. A novel method for characterizing current-carrying stability, based on correlation dimension, was proposed. When compared to copper, the correlation dimension decreased by 31.43%. It reveals that composites exhibit superior current-carrying stability compared to copper in salt-fog environment. The wear mechanism is further revealed. CNTs enhance the damage resistance of friction film, while MoS2 contributes lubrication. The appropriate addition of CNTs and MoS2 leads to the formation of an intact conductive lubrication anti-corrosion film on the surface, reducing the erosive impact of salt fog.

Fatigue and Fracture Evaluations in Ti-10V-2Fe-3Al (Ti 10-2-3)

A mechanical assessment was conducted to characterise the near β titanium alloy Ti-10V-2Fe-3Al (Ti 10-2-3), which was heat-treated to provide two strength variants. Low cycle fatigue and crack propagation tests were performed under standard laboratory air plus a salt fog environment. The differences in static strength were also demonstrated under fatigue conditions utilising plain specimens. However, the alloy was essentially insensitive to the test environment when comparing LCF performance in air and salt fog. Salt fog also provided no effect on crack growth behaviour. A double edge notch specimen geometry was employed to measure free initiation and the growth of cracks from a stress-raising feature. The current data now supplement previous studies aimed at expanding the mechanical database for Ti 10-2-3 component design and in-service life predictions.

Analysis of the Changes in the Mechanical Properties of the 3D Printed Polymer rPET-G with Different Types of Post-Processing Treatments

The paper deals with the actual topic of mechanical properties of 3D prints made from the polymer material rPET-G and its changes. Using this material in additive technology has great potential in the automotive industry. The research evaluates five different post-processing modifications of 3D prints from rPET-G (recycled polyethylene terephthalate-glycol) material produced by the Fused Filament Fabrication technology. The post-processing included the chemical smoothing of the samples using dichloromethane vapors and heat treatment in an annealing furnace. An epoxy resin, a synthetic coating, and a water-based coating were also applied. The standard was represented by samples without post-processing modifications, both in the form of recycled material and in the form of virgin PET-G. The texture of the samples was evaluated according to EN ISO 4287. Furthermore, the moisture absorption of the samples was evaluated using the gravimetric method according to EN ISO 62. The mechanical testing of the samples was carried out using a tensile test (EN ISO 527-2), a three-point bending test (EN ISO 178), impact strength (EN ISO 179-2), and a cupping test (EN ISO 1520). Degradation of the coatings took place using cyclic tests, which used a combination of exposure in a salt fog environment and in a climate chamber. The results of the experiments indicate that heat treatment appears to be a universal post-processing technology, as this method statistically improves not only the mechanical properties but also significantly reduces moisture absorption.

Epoxy resin/2-imidazole coated carbonyl iron powder: Synthesis, structure and corrosion performance

Magnetic metal absorbers are susceptible to strong corrosion in acid, alkali and salt fog environments, resulting in strong limitations of their applications. Therefore, it is urgent to develop magnetic absorber with enhanced anti-corrosion and microwave absorption. In this paper, carbonyl iron powder (CIP) coated with 2-methylimidazole/epoxy (2-MI/EP) composites were prepared by in-situ polymerization. The CIP@2-MI/EP composites showed better microwave absorption performance with a minimum reflection loss (RLmin) value of −54.11 dB at 9.69 GHz with 2 mm thickness. The electrochemical test results show that the corrosion current density of the composites decreases by two orders of magnitude and the corrosion potential is positively shifted to −0.1. In addition, the presence of 2-MI/EP layer can enhance the oxidation resistance of this composite. Considering the corrosion resistance, electromagnetic properties and oxidation resistance of this composite material, it provides an opportunity for valuable addition at commercial level.

Oxygenated Triazine-Heptazine Heterostructure Creates an Enormous Ascension to the Visible Light Photocatalytic Hydrogen Evolution Performance of Porous C3 N4 Nanosheets.

A highly efficient g-C3 N4 photocatalyst is developed by a novel one-pot thermal polymerization method under a salt fog environment generated by heating the aqueous solution of urea and mixed metal salts of NaCl/KCl, namely SF-CN. Thanks to the synergistic effect of the oxygenation and chemical etching of the salt fog, the obtained SF-CN is an oxygenated ultrathin porous carbon nitride with an intermolecular triazine-heptazine heterostructure, meanwhile, shows enlarged specific surface area, greatly enhanced absorption of visible light, narrowed band gap with a lower conduction band, and an increased photocurrent response due to the effective separation of photogenerated holes and electrons, comparing to those of pristine g-C3 N4 . The theoretical simulations further reveal that the triazine-heptazine heterostructure possesses better photocatalytic hydrogen evolution (PHE) capability than pure triazine and heptazine carbon nitrides. In turn, SF-CN demonstrates an excellent visible light PHE rate of 18.13mmolh-1 g-1 , up to 259.00 times of that of pristine g-C3 N4 .

Numerical Simulation of Contamination Accumulation Characteristics of Composite Insulators in Salt Fog Environment

To investigate the fouling characteristics of the composite insulator surface under the salt fog environment, the FXBW-110/120-2 composite insulator was taken as the research object. Based on the field-induced charge mechanism, the multi-physical field coupling software COMSOL was used to numerically simulate the fouling characteristics, explored the calculation method of ESDD, and demonstrated its rationality. Based on this method, the pollution characteristics of the composite insulator under the pollution fog environment were studied, and the influence of wind speed, droplet size, and voltage type on the pollution characteristics of the composite insulator was analyzed. The results showed that: with the increase in wind speed, the amount of accumulated pollution of insulator increases in the range of droplet size, and the relationship between wind speed and accumulated pollution is approximately linear; at the same wind speed, the amount of accumulated pollution increases with the increase of droplet size under the action of DC voltage; when there is no voltage, the amount of dirt on the upper surface of the insulator is more than that on the lower surface, while it is the opposite under DC voltage.

Research on Remote Automatic Monitoring Method of Atmospheric Salt Fog Concentration Based on Optical Sensor

The traditional automatic monitoring method of salt spray concentration has a weak anti-interference ability, which affects the monitoring accuracy. Therefore, a remote automatic monitoring method of atmospheric salt fog concentration based on optical sensor is designed. Determine the optical power loss of salt fog remote monitoring in atmospheric environment, and obtain the relationship between optical power loss and salt density, environmental humidity. Based on optical sensing, a quartz rod monitoring and early warning model under high salt fog environment is established to increase the surface area of the quartz rod, thus improving the anti-interference ability of the remote automatic monitoring device. The simulation experiment verifies that the monitoring method has higher monitoring accuracy and can be applied in real life.

Application of Infrared Spectroscopy in Research on Aging of Silicone Rubber in Harsh Environment.

Polymer insulators using silicone rubber materials as sheds and sheaths are widely used in power systems to replace traditional porcelain and glass insulators which are heavy, inconvenient to install, and prone to pollution flashover. However, in recent years, polymer insulators that have been operating in harsh outdoor environments for many years have experienced different degrees of aging. The aging degree and aging products of silicone rubber are the focus of research. Fourier transform infrared spectroscopy (FTIR) is a technical method to analyze the internal molecular bonds and functional groups of materials, and it is often used to study the aging degree and aging products of silicone rubber. In this paper, the aging characteristics of silicone rubber samples in a high altitude area, salt fog environment, and acid environment were studied by FTIR. The results showed that the silicone rubber in a harsh environment, such as strong radiation, salt fog, and acid fog was degraded to some extent, and its main chain was cut off, the degree of polymerization was reduced, and the content of hydrophobic functional groups was reduced. Infrared spectroscopy can be used to analyze the aging phenomenon of polymers.

Assessment of performance degradation of hybrid flax-glass fiber reinforced epoxy composites during a salt spray fog/dry aging cycle

The main goal of this paper is the evaluation of the performances reversibility of hybrid composites when they are dried after being aged in salt-fog environment. To this aim, epoxy composites reinforced with flax and glass fabrics respectively in the internal and external laminae were at first exposed to salt-fog (i.e., identified as wet phase) and then stored in controlled conditions (i.e., identified as dry phase). The flexural properties evolution of these composites as well as their water uptake and contact angle were monitored at varying time of both phases. The flexural strength and modulus of hybrid composites is 23.4% (17.9%) and 15.5% (12.9%) lower than unaged ones after 30 (15) days of salt-fog exposition, respectively. However, the dry phase allows an almost complete recovery of the composite performances. In particular, samples exposed to salt-fog for 30 days show an adequate recovery in the stiffness at the end of the dry phase, whereas their strength is about 10% lower than unaged ones. • Flax-glass hybrid composites were aged under alternated salt-fog and dry steps. • Flexural tests, water uptake and water contact angle measurements were performed. • Hybrid composites experienced reversible and irreversible degradative phenomena. • Due to the dry phase, hybrid composites showed an adequate recovery in flexural stiffness. • A topological map discriminating reversible and irreversible aging zones was proposed.

Study on Stress Corrosion Properties of 1Cr17Ni2 Stainless Steel

1Cr17Ni2 stainless steel is used in aviation, ships, machinery, and other fields. However, stress corrosion will lead to its strength reduction, thus failure. In this paper, we studied the stress corrosion resistance of 1Cr17Ni2 stainless steel bolts and nuts using fasteners’ stress corrosion test method and fasteners’ stress corrosion test method in a simulated environment with the accelerated stress corrosion test method of fasteners. The influence of seawater concentration, temperature, stress, test duration, and other parameters was fully considered during the test. The test results showed that 1Cr17Ni2 stainless steel would appear to stress corrosion crack under a specific corrosive environment, but the occurrence probability was not high. Therefore, in the complex seawater salt fog environment, the stress corrosion of 1Cr17Ni2 stainless steel cannot be ignored, which provides a practical reference for applying 1Cr17Ni2 stainless steel in a complex environment.

Study on Intermittent Fault Mechanism of Electrical Connector With Corrosion Degradation Under the Vibration Stress

With the continuous development of marine operations, the intermittent faults caused by the external salt fog environment threaten the safety of ship operations seriously. Among them, the intermittent fault of electrical connectors presents the major problem faced by ships. This article analyzed the mechanism of the intermittent fault of the electrical connector under salt-spray corrosion with and without vibration. In the meantime, the designs and vibration experiment of the electrical connector with corrosion degradation were carried out. In conclusion, the intermittent fault of the electrical connector is the main fault problem faced by ships.

Influence of anodizing surface treatment on the aging behavior in salt-fog environment of aluminum alloy 5083 to fiber reinforced composites adhesive joints

ABSTRACT The present work aims to evaluate how an innovative and eco-friendly anodizing process with tartaric-sulfuric acid (TSA) bath and a pore widening in an aqueous solution of NaOH 0.1 M can improve the durability in marine environment of co-cured adhesive joints between an aluminum alloy (AA 5083) and fiber (i.e., glass or basalt)-reinforced composite substrates. The aging was carried out by exposing samples to salt-fog spray conditions (5 wt.% NaCl) for 30, 60 and 90 days in a climate chamber, in accordance with ASTM B117. In order to get further insights on the aging behaviour of bonded joints, neat matrix was also exposed to the same environment for 60 days. Quasi-static mechanical tests and morphological analysis through SEM microscope coupled with EDX analyser were carried out to deeper understand how the fracture surfaces change during aging and how this affected the mechanical performances of joints.

Effect of Glass Fiber Hybridization on the Durability in Salt-Fog Environment of Pinned Flax Composites.

The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned laminates were exposed to a salt-fog environment for up to 60 days. Double-lap pinned joint tests were performed to assess the pin-hole joints performances at varying the laminate stacking sequence. In order to better discriminate the relationship between the mechanical behavior and the fracture mechanisms of joints at increasing the aging time, different geometries (i.e., by varying both the hole diameter D and the free edge distance from the center of the hole E) were investigated after 0 (i.e., unaged samples), 30 and 60 days of salt-fog exposition. It was shown that the hybridization positively affects the mechanical performance as well as the stability of pinned composites: i.e., improvements in both strength and durability against the salt-fog environment were evidenced. Indeed, the hybrid laminate exhibited a reduction in the bearing strength of about 20% after 60 days of aging, despite to full flax laminate, for which a total reduction in the bearing strength of 29% was observed. Finally, a simplified joint failure map was assessed, which clusters the main failure mechanisms observed for pinned composites at varying aging conditions, thus assisting the joining design of flax–glass hybrid laminates.

Effect of Underlayer Metallic Coating Composition on Phosphating and the Corrosion Performance for Automobile Applications

Automobile coating system consists of a metallic underlayer followed by a phosphate coating and, lastly, multilayer organic coating. In this work, the effect of the underlying metallic coatings, namely, a Mg-Al-Zn alloy coating (Magizinc [MZ]) and a conventional galvanized Zn coating on the phosphate coatings formed thereon, and its corrosion performance was investigated. The corrosion resistance offered by the phosphate coating formed on the MZ coating was higher than the phosphate coating on the galvanized Zn coating (a reference coating used in the study) in NaCl solution, as revealed by potentiodynamic polarization, electrochemical impedance spectroscopy, and salt-fog tests. In-depth characterization of the phosphate coatings was performed using scanning electron microscopy and glow discharge optical emission spectroscopy. It was revealed that the phosphate crystals formed on the MZ coating were more fine-grained, compact, and crack-free as compared to that formed on the galvanized coating and contained Mg aiding 4 to 10 times increase in the corrosion resistance as determined by the electrochemical studies. However, it only improved marginally against the appearance of red rust in a salt-fog test over the unphosphated MZ coating. The phosphate coating on MZ marginally improved the adhesion of an epoxy primer coating applied on the phosphated MZ coating and significantly (>3.5 times longer exposure) retarded the deterioration of the epoxy primer coating in the salt-fog environment in comparison with the similar studies performed on the phosphated conventional galvanized zinc coating. Notably, phosphating the MZ coating caused a 10 times reduction in the H pickup compared to that in the galvanized coating under identical phosphating conditions, suggesting the former coating lowered the propensity for hydrogen embrittlement in the steel.

One-pot scalable in situ growth of highly corrosion-resistant MgAl-LDH/MBT composite coating on magnesium alloy under mild conditions

Current corrosion-resistant layered double hydroxide (LDH) coating on Mg alloy is usually in situ grown in autoclave by hydrothermal methods under high temperature and high-pressure conditions, which is unfavorable for industrial application. We report that an inhibitor (2-mercaptobenzothiazole, MBT) incorporated composite (MgAl-LDH/MBT) coating can be in situ deposited on bare AZ31 Mg alloy surface with the assistance of a chelating agent (ethylenediaminetetraacetic acid) under a relatively low temperature (95 °C) and ambient pressure by a one-pot method. The successful formation of LDH/MBT composite coating is confirmed by a series of characterizations, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). The corrosion resistance of the composite coating is evaluated by means of hydrogen evolution measurement, electrochemical impedance spectroscopy (EIS), Tafel polarization curves, and neutral salt spray test. The tests show that the LDH/MBT composite coating has a very low corrosion current density (1.73 10−8 A cm−2), an extremely high charge transfer resistance (2.336 MΩ cm2), and does not show any corrosion pits even after 15 d of exposure to a NaCl solution or 7 d of exposure to salt fog environment, manifesting the good and robust corrosion protection. Lastly, the deposition and corrosion protection mechanisms of the MgAl-LDH/MBT composite coating are also discussed and proposed based on the EDS characterization of the coating after long-time exposure.

Chain dynamics evolution of ethylene‐propylene‐diene monomer in response to hot humid and salt fog environment

AbstractThis work is dedicated to the mechanism underlying the influence of the harsh environment that may cause accelerated aging (high temperature, humidity, and salt spray) on the static and dynamics characteristics of ethylene‐propylene‐diene monomer (EPDM) copolymer. A molecular dynamics simulation was employed to provide an insight into the effects of the hot humid and salt fog environment on the micro and macroscopic properties. First, evidence shows that the Tg obtained by fitting mean square displacement does not rely on the selection of the equilibrium time. Second, radial distribution function, chain configuration, and nonbonding interaction were analyzed and it is inferred that the ambient humidity and temperature show a significant synergy on the EPDM system, which is attributed to the aggregation state transition and diffusion behavior of partial water at high temperatures. Finally, water and salt were considered as two factors to explore the influence on the Tg and the mobility of the molecular chain. It is concluded that the existence of water molecules significantly affects the chain dynamic behavior of EPDM, while salt is not regarded as an influencing factor. In general, our simulated work provides some insights and guidance for the durability of EPDM when used in harsh environments.

Root cause analysis of pitting corrosion of AA2024 and AA7075 after exposure in salt fog environment

Root cause analysis of pitting corrosion of AA2024 and AA7075 after exposure in salt fog environment