Salt Spray Corrosion Research Articles

Effects of salt spray corrosion on low cycle fatigue properties of a ferrite-bainite weathering steel

Effects of salt spray corrosion on low cycle fatigue properties of a ferrite-bainite weathering steel

Investigation of corrosion resistance offered by the Fe-based clad layer under salt spray and electrochemical workstations

The present work aims to evaluate the electrochemical characteristics of the Fe–based alloy coating formed on the 27SiMn steel substrate under neutral salt spray and 3.5 wt% NaCl environments. By adopting the high-speed laser cladding technique, the Fe-based clad layer was fabricated to perform microstructural and electrochemical characterizations. The microstructure and phase of the coating were analyzed using a scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), and its corrosion performance was also discussed using the salt spray corrosion chamber and the electrochemical workstation. The results show that the microstructure of the coating surface contains equiaxed crystals and long dendritic crystals which arise due to the higher solidification rate after the cladding process. The Fe–based coating was rich in FeCr phase throughout its microstructure without the formation of the intermetallic compounds. Compared to the substrate, the corroded surface of the coating tends to be compact containing a few corrosion pits after different corrosion times, which is attributed to the formation of Cr oxide on it. The electrochemical tests on the potentiodynamic polarization curve (PPC) and electrochemical impedance spectrum (EIS) indicate that the corrosion resistance of the coating is superior to the substrate, presenting a higher corrosion potential (−0.298 V), lower passive current density (1.36 × 10−6 A•cm2), and higher charge transfer resistance (8.23 × 106 Ω·cm2). Additionally, the corrosion mechanism of coating in salt spray and electrochemical tests is the local pitting corrosion due to the autocatalytic effect on the localized region, which facilitates Cl− ions penetrating the coating and leads to the dissolution of Fe and Cr oxides.

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.

Hot-dip galvanizing process and coating corrosion behavior of fe-mn-al-c steel

The temperature of the zinc bath and the immersion duration are critical factors that significantly impact the surface quality and adhesion of batch hot-dip galvanizing coatings. This study focuses on the influence of different zinc bath temperatures (460, 490, and 520 °C) and immersion duration (1, 3, 5, and 10 min) on the hot-dip galvanized coatings of Fe-Mn-Al-C lightweight steel, which were characterized using scanning electron microscopy and energy dispersive X-ray analysis. The results demonstrate that with the increasing zinc bath temperature and immersion duration, the coating thickness and bond strength initially increase and then decrease. The inhibition layer in the coating gradually fractures and thickens with the rising temperature, leading to changes in the alloy phases within the coating. The optimal batch hot-dip galvanizing condition for the experimental steel is immersing at 490 °C for 3 min. Furthermore, we conducted a neutral salt spray corrosion test on the specimens under the optimal batch hot-dip galvanizing condition to study their corrosion behavior and mechanism and evaluate the impact of batch hot-dip galvanizing on the corrosion resistance of Fe-Mn-Al-C steel.

Study on mechanical properties of locally corroded square steel tube short column

To investigate the axial compressive properties and failure modes of 18 locally corroded square steel tube short columns, salt spray corrosion tests were conducted. The findings indicate that local corrosion in the horizontal direction significantly impacts the ultimate bearing capacity of the specimens, with all failures occurring in the corroded areas. However, the influence of the corrosion area on the ultimate bearing capacity and ductility of the specimens is not evident. A local corrosion model for square steel tube short columns was developed using the finite element method. The ultimate bearing capacity determined through finite element simulation closely aligns with experimental results, validating the reliability of the simulation approach. Moreover, a comparison is made between the prediction models of the BP neural network and the GA-BP neural network, with the prediction effectiveness of each model evaluated using the leave-one-out method. The verification results indicate that the GA-BP neural network model demonstrates superior predictive performance, with an average error of 3.14%.

Effect of Fatigue and Precorrosion Fatigue on Fatigue Crack Propagation and Fracture Failure Behavior of 5B70 Aluminum Alloy

Aluminum alloys are ideal lightweight structural materials for spacecraft, but they are susceptible to local corrosion during service. Herein, a systematic investigation is carried out to determine the fatigue behavior of 5B70 aluminum alloy under salt spray precorrosion. The mechanism of salt spray corrosion, fatigue life, crack propagation, and failure fracture mechanism of 5B70 aluminum alloy are studied. Under the salt spray corrosion, 5B70 aluminum alloy mainly undergoes pitting corrosion via a galvanic corrosion mechanism. After precorrosion, the formation of macroscopic fatigue cracks is accelerated, which significantly reduces its fatigue life. Fracture occurs due to single crack initiation and propagation under fatigue conditions. The fatigue crack tip undergoes a mixture of intergranular and transgranular modes, but mainly transgranular mode. Multiple strain localization phenomena occur during precorrosion fatigue, and corrosion pits on the surface provide a tortuous crack propagation path; the fatigue crack tip is mainly transgranular mode.

The Effect of Artificial Ageing on the Changes in Selected Properties of Organic Coated Sheets.

This contribution presents the results of research focused on changes in selected properties of organic-coated steel sheets in a corrosive environment of salt mist. The aim of this study was to characterise coated sheets and to analyse the influence of elevated temperature on changes in their selected properties. The methodology and experiments were chosen to simulate the accelerated ageing and to evaluate the surface of organic-coated steel sheets. During the research, the effect of artificial ageing due to increased temperature on changes in mechanical properties of coated sheets was monitored, which were determined by tensile testing according to STN EN 10002-1. The fracture surface of the test samples was analysed using a SEM. The following observations were made for the evaluation of coating by cross-cut tests according to EN ISO 2409. Corrosion tests were carried out by conducting salt spray corrosion tests according to EN ISO 9227. The test specimens were artificially sectioned using a laser beam. The results of the research experiments confirmed the assumption that the utilisation of the laser beam was convenient for the creation cross-cut test of the material. After the ageing test, only small significant changes in the basic mechanical properties of the tested materials were observed. It is necessary to take into account that there were changes in the appearance of the coating. The cross-cut test confirmed the results that the plastic-coated sheets could be utilised in salt corrosion environments.

Controllable size of graphite nanosheets and functionalized SiO2 microspheres with excellent anti-corrosive/wear function for superhydrophobic coating

The application of superhydrophobic coatings is limited by their complex fabrication process, expensive modification, and lack of durability. This study addresses these issues by proposing a simple and economical method for fabricating strong superhydrophobic coatings by scraping off the fluorinated suspension. This coating comprises epoxy resin (EP), graphene nanosheets, and modified silicon oxide on the Q235 steel substrate. The contact angle and sliding angle of we prepare the coating coating are 152.3° and <10° respectively, exhibiting excellent super-hydrophobicity. After being immersed in 3.5 % sodium chloride solution for 1440 minutes, the coating shows a resistance of 1.14×106 Ω cm2, which is two orders of magnitude higher than that of the coating immersed for 30 minutes (1.08×104 Ω cm2), indicating its excellent corrosion resistance. A 30-day salt spray corrosion test also confirms the good corrosion resistance of the coating. When the coating is polished 100 times under a load pressure of 500 g on 1000-mesh sandpaper, the contact angle is only reduced by 7 times, indicating its good abrasion resistance. In addition, the coating also has good weather resistance and self-repairing ability against ultraviolet radiation. This simple and environmentally friendly manufacturing method has great potential for large-scale practical applications in many fields.

Research on the influence of major ions in weakly alkaline mine water on anchor cable corrosion and protection technique

Anchor cables in water-rich roadways frequently experience severe corrosion and resultant fractures due to the combined effects of mine water and high stress. However, the precise factors influencing corrosion on these cables remain ambiguous, presenting challenges to roadway support safety. This study investigated the impact of major ions present in weakly alkaline mine water on anchor cable corrosion using salt spray corrosion experiments. The results indicated that major anions such as Cl- notably influence anchor cable corrosion, which primarily manifested as pitting corrosion. The nominal yield strength decreased by 95.68–156.01 MPa, and the nominal tensile strength decreased by 133.44–202.77 MPa because of a decrease in the cross-sectional area. During the corrosion process, major anions such as Cl- continuously degraded the passivation film on the surface of the anchor cable, exposing its internal metal structure and exacerbating corrosion until eventual fracture failure occurred. Therefore, this paper proposes a corrosion protection technique for mine anchor cables to realize superior protective effects compared to conventional anchor cables used concurrently in field applications.

An effective utilization of raw fly ash obtained from thermal power plants using thermal spray technique to improve corrosion resistance for marine applications

Marine-grade steel structures in offshore environments often corrode due to the aggressive environmental conditions. Many ceramic materials can cater to this demand. However, as per economic and ecological concerns, fly ash (FA), an industrial waste, can be another strong contender to control corrosion. Therefore, the present study developed composite coatings of fly ash with additives ((50-48) wt.% Al2O3; 0–2 wt% carbon nanotube (CNT)) onto marine-grade steel using a plasma spray technique to improve its corrosion resistance. The microstructure of 1 wt% CNT-reinforced alumina-FA (1CAF) coating was denser than 2 wt% CNT-reinforced alumina-FA (2CAF) coating due to the uniform dispersion of CNT and, thereby, uniform remelting of coating at localized sites. Consequently, the microhardness and adhesion strength of the 1CAF coating were improved by ∼14.66 % and ∼15.96 %, respectively. Further, Rietveld's analysis of coatings showed that quartz, being the primary phase for corrosion control, was 19.23 ± 0.87 %, 16.33 ± 1.04 % and 14.60 ± 1.87 % for alumina-FA (AF), 1CAF, and 2CAF, respectively. The electrochemical impedance spectroscopy and the salt spray corrosion tests showed that 1CAF coating corrosion resistance was improved by ∼11.2 % compared to AF coating, even with a lower quartz phase (∼15.08 %) due to the densification of coating. This densification was due to the remelting by CNT to seal pores in the coating. Furthermore, for the same reason, an increase in coating resistance and charge transfer resistance of 1CAF coating by ∼80.9 % and ∼19.93 %, respectively, were seen in the equivalent circuit analysis, showing great promise in controlling interfacial corrosion. Further post-treatments like plasma or laser treatments can seal the coatings further to improve corrosion resistance. Therefore, such coatings are expected to withstand harsh, corrosive environments and are well-suited for marine applications.

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.

Research and development of corrosion monitoring sensor for bridge cable using electrical resistance probes technique

A cable corrosion monitoring sensor with a temperature compensation probe has been designed and manufactured to monitor the corrosion of high-strength steel wires in the transition zone between the cable body and the anchorage. The influence of temperature and tensile force on the resistance of steel wires was thoroughly investigated. Reliability tests were conducted on the temperature compensation probe, along with salt spray corrosion tests on the corrosion sensor. The research results demonstrated that, compared to the temperature sensor, temperature compensation probe can better reflect the actual temperature of the corrosion sensor and provide effective temperature compensation for the corrosion sensor. Moreover, the developed corrosion sensor can effectively reflect the mass loss rate of the corrosion probe. The sensor is capable of detecting a corrosion level as low as 0.02 % of the complete steel wire mass, which corresponds to an average corrosion depth of 0.412 μm.

Microstructure and Salt Spray Corrosion Behaviors of Welded Joints of 304/HRB400 Clad Rebars

Microstructure and Salt Spray Corrosion Behaviors of Welded Joints of 304/HRB400 Clad Rebars

Effect of Salt Spray Corrosion Performance on Variable Polarity Plasma Arc Welding of Aerospace Aluminum Alloy

Effect of Salt Spray Corrosion Performance on Variable Polarity Plasma Arc Welding of Aerospace Aluminum Alloy

Effect of impact-corrosion coupling damage on fatigue properties of 2198-T8 aluminum-lithium alloy

The peeling of aircraft surface paint due to foreign object impact can expose the aluminum–lithium alloy substrate to atmospheric corrosion, resulting in the fatigue performance being affected by the combined effect of impact damage and corrosion damage. In this work, the effects of impact damage and corrosion damage on the fatigue life of 2198-T8 aluminum–lithium alloy sheet were investigated. The strain field distribution of specimens with coupled impact and corrosion damage under cyclic loading was analyzed by Digital Image Correlation (DIC) technique, and the coupling relationship between impact and corrosion damage was analyzed based on the crack propagation path and fracture morphology. The results show that surface corrosion pits depth distribution of impact dents follows the same trend as residual stress distribution. For the coupling damage of the hemispherical punch, the coupled effect between impact damage and corrosion damage is most evident at low impact energy. At higher impact energies, the impact damage dominates the coupling damage. As the salt spray corrosion time increases, the fatigue life decrease rate gradually slows with increasing impact energy, and the impact damage has a greater effect on the fatigue life in the early corrosion stage. Compared to the salt spray corrosion environment at 35 °C, the fatigue life of the specimen at 25 °C increased by a maximum of 50.48 % as the impact energy increased from 10 J to 25 J.

Environmental test and evaluation technology of control and protection device for flexible DC converter valve

Environmental suitability is particularly important for the safe and reliable operation of the product. The environmental test and evaluation method are studied to target the reliability requirements for the control and protection device of the flexible DC converter valve. According to the characteristics of the secondary board card of the control and protection device, a study is carried out on the mechanism of salt spray corrosion, and specific methods for implementing and evaluating the salt spray test are proposed. Using this method, a salt spray test is conducted on a secondary board card of a relay control and protection device under the finalization of the design. The test results show that this method can effectively reveal the salt spray corrosion weakness of the product. Besides, salt spray test results are also evaluated according to the corrosion conditions of the product after the test. The application of environmental test and evaluation technology of the control and protection device of the flexible DC converter valve has a significant meaning in improving the reliability of relevant products.

Corrosion Behavior of 30 ppi TAD3D/5A05Al Composite in Neutral Salt Spray Corrosion

This study created ceramic preforms with a 3D network structure (TAD3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD3D. The corrosion behavior and resistance of TAD3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl2O4, Al(OH)3, and Al2O3. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion.

In-situ crosslinking reaction of graphene oxide & waterborne epoxy resin to construct continuous phase anticorrosive coating

The mechanism of using graphene oxide as a two-dimensional filler to increase the path length of the corrosive medium to the metal surface is limited to improving the corrosion resistance of the coating. This study propose novel dispersion and in-situ crosslinking reaction mechanism for constructing water-based heavy-duty anticorrosive coatings by using graphene oxide (GO) and waterborne epoxy resin (WEP). The results showed that GO can be uniformly dispersed directly into WEP without complex functional modifications. Oxygen-containing functional groups on moleculars structure of GO&WEP co-polymerized with diethylenetriamine (DETA) forming a continuous phase film which improved the density of the coating. Characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal conductivity measurement instrument, pencil hardness tester, adhesion tester, salt spray corrosion test chamber, and electrochemical impedance spectroscopy (EIS) were used to evaluate coating structure and performance properties. The results showed that graphene characteristics enhanced physical properties and anti-corrosion performance of composite coatings. The construction mechanism of the coating is different from that of the current GO modified and dispersed in the coating as a two-dimensional filler to extend the path length of the corrosive medium to the metal surface. The coatings prepared by adding the optimum mass ratio of 0.1–0.2 % GO to WEP have the best physical properties and anti-corrosion properties. When the GO content is 0.2 wt%, the thermal conductivity increases by 86.0 %. After added 0.025 wt% GO, the coating hardness is increased by two grades directly from 2B to HB. With the addition of GO concentration increased to 0.05 wt%, the adhesion is increased from 2 to level 1.When the GO content exceeds 0.05 %, the coating will not bulge off after 4 months of salt water immersion experiment.

Effect of Iron Content on the Pitting Corrosion Behavior of Laser-Cladded Ni-Cr-Mo Alloy Coating in a Simulated Seawater Environment

In order to study the effect of iron content on the pitting corrosion behavior of a Ni-Cr-Mo alloy coating in a simulated seawater environment, a Ni-Cr-Mo-xFe (x = 0, 5, 10, 15, 20, 25) alloy coating was prepared through laser cladding technology. These coatings primarily consist of a γ-Ni solid solution phase, with observable iron segregation in the interdendritic regions when the iron content reaches 25 wt%. After 42 days of salt spray corrosion, it was found that pitting began to appear on the surface when the iron content in the coating increased to 10 wt%. The results of electrochemical behavior revealed that the coatings with iron contents in a range of 10–25 wt% exhibited metastable pitting characteristics, and the impedance modulus decreased with the increase in iron content. Pitting corrosion occurs due to selective corrosion of the dendritic regions. When the iron content exceeds 10 wt%, the accumulation of iron in the outer layer of the passivation film would lead to an excess of cationic vacancies, and the stability of the passive film is then reduced. This study provides a reference for the control of the iron content in a Ni-Cr-Mo alloy coating when applied in marine environments.

Fatigue Behavior and Fracture Surface Analysis of Corroded High-Strength Bridge Cable Wires.

Bridge cable wires suffer from alternating stress and environmental erosion, leading to premature failure prior to its design life. This paper investigates the fatigue and mechanical behaviors of corroded bridge cable wires with a zinc-aluminum (Zn-Al) alloy coating. Based on the salt spray corrosion test and microstructure analysis, the anti-corrosion resistance and corrosion appearance characteristics of the Zn-Al alloy coating and galvanized coating were investigated. The Zn-Al alloy coating was superior in resistance to corrosion fatigue for the improvement in toughness and the generation of anti-corrosion Zn-Al and Fe-Zn-Al phases. Equations of the accelerated corrosion depth of the steel wires had been regressed to roughly estimate the corrosion life of the Zn-Al alloy coating, which can reach 29.1 years with a thickness of 70 μm. The fatigue and mechanical properties of the bare wires after the salt spray test were further studied based on tensile tests and fatigue tests. The fatigue properties of the bridge cable wire would decrease with the corrosion degree due to the deterioration and embrittlement of materials, where ductility characterized by the elongation rate was the most affected. Fracture surfaces of the wires were captured and analyzed based on a method for recognizing graphical contours. Insufficient fatigue life may occur in the steel wires after corrosion and increase with the degree of corrosion. The pit depth logarithmically weakened the fatigue life of steel wires for the weakening of fatigue toughness and the bearing area. The flat fracture was more common with a single fatigue source, while multiple fatigue sources led to step-like fractures for the generation of multiple dispersed crack propagation regions. Corrosion fatigue was more sensitive to the existence of fatigue sources than the reduction. Multiple initiation sources significantly reduced the fatigue life due to the cracking facilitation of the joint effect of multiple pits. The electrochemical reactions of corrosion can lead to material embrittlement and a reducing effect on the fracture toughness of the steel wires.