Salt Fog Test Research Articles

New type of tri‐pyridyl inhibitor‐loaded polyaniline nanospheres for durable protection anticorrosion coatings

AbstractPolyaniline (PANI) is considered as one of the most promising corrosion inhibitors because of its unique redox and environmental stability. Pyridine and its derivatives can chelate metal ions during corrosion, forming an inert protective layer on the metal surface to achieve the anticorrosion effect. Therefore, polyaniline is combined with pyridine together to achieve deep anticorrosion in this work. 4‐((2,2′:6′,2″‐terpyridin)‐4′‐yl)aniline (TPY) and 1,3,5‐benzenetricarbonyl chloride (TMC) were applied to synthesize a novel corrosion inhibitor N1, N3, N5‐tri (4‐((2,2′: 6′, 2′‐tri‐pyridine)‐4′‐yl) phenyl) benzene‐1,3,5‐tri‐formamide (TBT). Then, TBT was in situ loaded onto the PANI surface to obtain the composite TPANI. The TPANI was successfully dispersed in epoxy resin (EP) at various dosages to prepare composite coatings. Electrochemical impedance spectroscopy and salt fog tests were employed to evaluate the performance of the coatings. After experimentation, we discovered that when the TPANI content was 0.25 wt%, the impedance value remained stable at 5.83 × 109 Ω cm2 after immersing the coatings in a 3.5 wt% NaCl solution for 28 days. In contrast, the EP coating exhibited a resistance decrease ranging from 9.56 × 109 to 7.8 × 108 Ω cm2 within the same soaking time, decreasing by an order of magnitude, while the TPANI‐0.25% coating still maintaining a high order of magnitude. These results indicated that the TPANI filler effectively preserved long‐term stability and provided persistent protection against corrosion. The protective mechanism of TPANI composite coatings was further elucidated through detailed analysis. Overall, the incorporation of TPANI into the epoxy resin yielded promising results, demonstrating its potential as an effective corrosion inhibitor for protective coatings.

Durability of Single Lap Friction Stir Welded Joints between S355-J0 Steel and AA5083 Aluminum Alloy–Mechanical Tests

This study aims to investigate a friction stir welded joint between steel and aluminum alloy. FSW is nowadays one of the most interesting joining techniques due to the possibility of connecting materials and thicknesses that are difficult or impossible to weld with traditional techniques. The main advantage is that materials are not affected by thermal cycle problems during solidification and cooling, and the absence of fumes and pollution during the process favors the quality of the welded joint. The life of metal joints could be greatly reduced in a corrosive environment since the less noble material will tend to increase its corrosion rate, while the nobler one will reduce its electrochemical dissolution. Accelerated aging tests (i.e., salt fog test) are used to estimate the lifetime of metal joints in highly aggressive environments. The aim of the present work is to evaluate the durability at a long aging time in the salt spray test (according to ASTM B117) of carbon steel/aluminum alloy joints, obtained by FSW. In this first part, mechanical test results are reported. A deep metallographic and chemical investigation is going to be reported in part two. The current research work investigates the welding direction and residence time in the salt spray chamber. The breakage of all tested samples, evaluated after the tensile tests were carried out, always occurs at the interface of the joint, regardless of the change of direction of the weld on the advancing or retreating side. The welding direction influences the breakage of the joint only before the aging treatment. Specifically, specimens produced in advance are characterized by increased joint strength. On the other hand, the factor that influences the performance of the joints is the exposure time where, starting from the first point of aging, i.e., after two months, there is a decrease in the maximum load of 40%, and the effect of corrosion leads to a significant deterioration of the weld which remains almost similar until the last point of aging.

Alloy selection for wear-resistant lightweight aluminium brake disc

Brake discs for the rear axle of a high-performance sports car have been manufactured in three different lightweight materials; AA6082, AA7075 and AA2024 aluminium alloys. These were subsequently coated with a Keronite plasma electrolytic oxidation (PEO) ceramic layer. Full-scale dynamometer tests have been conducted against a standard low-met brake pad using a modified AK master test at increasing levels of braking temperature until a physical limit is reached. Microstructural characterisation of coating and brake pad wear and tribo-layer have been studied using SEM and EDX. In addition, post-dynamometer-test friction discs have been exposed to salt fog testing. Dynamometer tests give confidence that PEO-coated aluminium brake discs are a viable technical solution for vehicle lightweighting. In particular, compelling performance with respect to good coefficient-of-friction (CoF), extremely high coating adhesion, minimal disc and pad wear, low disc run-out, good heat dissipation, and good corrosion resistance has been demonstrated for Mat A (AA6082) alloy discs. Despite higher room temperature strength, the resulting performances of Mat B (AA7075) and Mat C (AA2024) are poor at higher braking temperatures, resulting in excessive coating spallation and subsequent grain boundary attack followed by severe intergranular corrosion.

Flashover voltage and time prediction of polluted silicone rubber insulator based on artificial neural networks

Insulator flashover prediction is an important task that should be done before any hazards. In this paper, leakage current (LC) analysis using neural networks is utilized to predict the flashover voltage (FOV) and flashover time (FOT). Experiments are performed on silicone rubber (SiR) insulators in the salt fog test chamber under different conditions and levels of contamination for LC sampling. To predict flashover, sampled LC at different contamination levels are first clustered by the self-organizing map (SOM) artificial neural network (ANN). Clustering results and other factors are employed to level the situation of LC periods. Afterward, these levels are fed sequentially to another ANN to predict the FOV and FOT. Various sample data are tested and compared with Back Propagation (BP) and Multilayer Perceptron (MLP) neural networks to evaluate the proposed neural network and algorithm. The results confirm the acceptable performance of the proposed neural networks and their ability as an online monitoring system to raise alarms before potential flashover hazards.

Corrosion behaviour of microstructurally modified elastic rail clip steel under crevice and aggressive salt fog exposure

In the present work, existing Indian elastic rail clip steel (tempered martensite) is microstructurally modified to bainite using austempering route. Crevice corrosion of elastic rail clip (ERC) is of major concern as metal dissolution can cause the loosening of the rail clip assembly (such as rail clipinsert and rail clipliner) and lack of performance. Furthermore, the surface of rail clip exposed to the atmosphere could also be affected by the corrosive environment. The present work concentrates on the findings of crevice corrosion and wetdry salt fog exposure of the austempered ERC steels in 3.5 wt% NaCl solution for 30 days and compared with the asreceived (existing) ERC steel which consists of tempered martensitic structure. The severity of corrosion has been investigated by studying the surface dissolution and the rust formed on the exposed surfaces of the ERC steels after the crevice and salt fog tests. Scanning electron microscopy (SEM) and optical profilometry have been used for the analysis of surface dissolution behaviour. Moreover, the rust formed on the exposed surfaces characterised using SEM shows the presence of various rust phases, such as αFeOOH, βFeOOH, γFeOOH, αFe2O3, etc. Furthermore, Raman spectroscopy has been used for the confirmation and quantification of these rust phases. The higher protective ability index (PAI) calculated from the quantitative assessment of different rust measured from Raman spectroscopy shows the better corrosion resistance of the austempered ERC stee

Environmental Robustness and Resilience of Direct-Write Ultrasonic Transducers Made from P(VDF-TrFE) Piezoelectric Coating

Conformability, lightweight, consistency and low cost due to batch fabrication in situ on host structures are the attractive advantages of ultrasonic transducers made of piezoelectric polymer coatings for structural health monitoring (SHM). However, knowledge about the environmental impacts of piezoelectric polymer ultrasonic transducers is lacking, limiting their widespread use for SHM in industries. The purpose of this work is to evaluate whether direct-write transducers (DWTs) fabricated from piezoelectric polymer coatings can withstand various natural environmental impacts. The ultrasonic signals of the DWTs and properties of the piezoelectric polymer coatings fabricated in situ on the test coupons were evaluated during and after exposure to various environmental conditions, including high and low temperatures, icing, rain, humidity, and the salt fog test. Our experimental results and analyses showed that it is promising for the DWTs made of piezoelectric P(VDF-TrFE) polymer coating with an appropriate protective layer to pass various operational conditions according to US standards.

Superhydrophobic and Durable Silver-Coated Fabrics for Efficient Electromagnetic Interference Shielding

Superhydrophobic surfaces present promising potential for improving the mechanical and chemical durability of electromagnetic interference (EMI) shielding materials. However, integrating superhydrophobicity and EMI shielding is still a challenge due to the complex structural design. Herein, superhydrophobic and highly durable fabrics with excellent EMI shielding effectiveness were fabricated. First, the meta-aramid nonwoven fabrics were functionalized by a polydopamine layer. Then, with the assistance of the metal-binding ability of polydopamine, silver nanoparticles were immobilized on the fiber surface by electroless plating. Finally, after the introduction of fluorine-containing agents via a facile dipping method, a superhydrophobic surface was successfully obtained. The as-prepared fabrics showed excellent EMI shielding effectiveness of 111 dB due to superior electrical conductivity (234 S/cm). Moreover, thanks to the low surface energy of fluorine-containing molecules as well as the micro-nanoroughness created by the stacking of silver nanoparticles, the composite fabrics exhibited a large water contact angle of 152° and a low sliding angle of 5°. It was noted that the composite fabrics still maintain superhydrophobicity and high EMI shielding effectiveness (110 dB) even after the acid and alkali corrosion, bending, abrading, and salt fog test, respectively, demonstrating their durability under harsh environments.

Microstructure and Salt Fog Corrosion of Wrought Mg-Al-Zn and Mg-RE Alloys.

Wrought magnesium alloys have received attention due to their potential application as lightweight materials. However, their use is limited by their poor corrosion resistance. Rare earth additions have the potential to enhance corrosion resistance. The present work included a microstructural investigation and corrosion testing of the alloy WE-43, containing Nd and Y, which was compared against the more conventional compositions of AZ31 and AZ61 alloys. All three alloys exhibited a recrystallized equiaxed structure after hot rolling with the presence of second phases-precipitates. The WE-43 alloy exhibited a better corrosion resistance than AZ31 and AZ61 under salt fog testing, indicated by the lower depth of attack and lower weight loss. The second phases in the microstructure of AZ31 and AZ61 alloys determined their corrosion resistance. The second phases in the AZ31 and AZ61 alloys (based on Al-Mg and Al-Mn phases) were nobler than the Mg matrix and catholically acted, thus sacrificing the Mg matrix. The superior corrosion resistance of WE43 was due to the incorporation of Y in the oxide/hydroxide film. In addition, the second phases in the WE43 consisted of Nd and Y and were less noble than the Mg-matrix. Thus, they acted as anodic sites protecting the Mg-matrix. The above results show the beneficial effect of rare earth additions to wrought Mg alloys towards increased corrosion resistance.

Evaluation of Long-Term Boiling Water Immersion as Artificial Aging Test of Silicone Rubber Insulators

Our country IRAN have long coastal area with length of more than 1830 km. Utility companies with 30 years of experience in using polymeric insulators in this very heavy polluted area. Operational history in these areas indicates many insulating problems. With the advancement of polymer insulation technology, the utilities want to select the longest life insulators for these areas. Laboratory studies accelerated testing of polymer insulators is the only available method to investigate the trend of insulator degradation during the aging process, because it takes a long time for noticeable changes and signs of aging to appear on insulators in the power grid. Different methods such as salt-fog, UV and boiling water are used to test artificial aging, each method has advantages and disadvantages. In our experience, boiling water is used as a low-cost method in compared to the other methods especially salt fog test. The aim of this research was to determine a shorter method for evaluation of SR insulators. In this paper, the accelerated aging of polymer insulators using salt-fog and boiling water immersion tests are investigated. During and after the aging test, the polymer insulator's electrical quality is analysed using leakage current measurement tools, partial discharge, and hydrophobicity. Surface changes are also analysed by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), Thermo Gravimetrical Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) both qualitatively and quantitatively.

Textile Knitted Stretch Sensors for Wearable Health Monitoring: Design and Performance Evaluation

The advancement of smart textiles has led to significant interest in developing wearable textile sensors (WTS) and offering new modalities to sense vital signs and activity monitoring in daily life settings. For this, textile fabrication methods such as knitting, weaving, embroidery, and braiding offer promising pathways toward unobtrusive and seamless sensing for WTS applications. Specifically, the knitted sensor has a unique intermeshing loop structure which is currently used to monitor repetitive body movements such as breathing (microscale motion) and walking (macroscale motion). However, the practical sensing application of knit structure demands a comprehensive study of knit structures as a sensor. In this work, we present a detailed performance evaluation of six knitted sensors and sensing variation caused by design, sensor size, stretching percentages % (10, 15, 20, 25), cyclic stretching (1000), and external factors such as sweat (salt-fog test). We also present regulated respiration (inhale-exhale) testing data from 15 healthy human participants; the testing protocol includes three respiration rates; slow (10 breaths/min), normal (15 breaths/min), and fast (30 breaths/min). The test carried out with statistical analysis includes the breathing time and breathing rate variability. These testing results offer an empirically derived guideline for future WTS research, present aggregated information to understand the sensor behavior when it experiences a different range of motion, and highlight the constraints of the silver-based conductive yarn when exposed to the real environment.

Electrochemical response and passivation affinity of Fe-based amorphous HVOF coatings prepared from pig iron on mild steel

The present work discusses the passivation tendency and corrosion resistance of a novel Fe66.59C11.70P7.58Mn0.37Si2.86Cr1.72Mo0.92B8.26 amorphous coating prepared from pig-iron deposited on mild steel using a high-velocity oxy-fuel (HVOF) thermal spray process. A quantitative assessment of the micromorphological features developed on each coating after the fabrication has been provided. The polarization response, current-transient at the potential in the passive zone, and gravimetric evaluations after 30 days of the salt-fog test using 3.5 w/v % NaCl solution were recorded to understand the overall corrosion behavior of the HVOF coatings. A steady-state electrochemical impedance measurement was also performed. The spectroscopic examination of the corrosion product was performed to understand the nature of passivation, and it revealed the formation of protective iron-chromate and phosphate phases on all the coatings. The synergistic effect of these protective phases and iron-based protective rust phases is believed to be the primary reason for the strong passivation of the coatings. Also, it has been proposed that the corrosion rates calculated from dynamic polarization response should not be considered as final assessment for corrosion resistance of the coatings. Rather, long term corrosion assessment is important to understand the benefit of amorphous coatings with lean chemistry of passive elements, like Cr.

INVESTIGATION OF THE EFFECT OF MULTI-LAYER COATING ON CORROSION PREVENTION PERFORMANCE FORMED BY THE APPLICATION OF SOLVENT-BASED ZINC LAMEL COATING ON ALKALI ZINC AND ALLOY ZINC COATING

Bu çalışmada, alkali çinko, çinko-nikel ve çinko-demir alaşım kaplama prosesleri ile çözücü bazlı çinko lamelli kaplama prosesi yeniden düzenlenerek bir araya getirilmiş ve iki farklı kaplama prosesinin tekil üstün özellikleri birleştirilerek üstün korozyon önleme performansına sahip ürünlerin üretilmesine olanak sağlayan yeni bir proses geliştirilmiştir. Yürütülen deneysel çalışmalar sonucunda elde edilen ve görsel uygunluk kriterini sağlayan kaplamalar kuru yapışma, su direnci, nem direnci, tuz sisi, çevrimsel korozyon ve kimyasal direnç testlerine tabi tutulmuştur. Geliştirilen yeni proses, yüksek korozyon direncine (>1000 saat tuz sis testi ve >63 döngü döngüsel korozyon testi), yüksek sıcaklık direncine (300 °C'de bir saat), kimyasal dirence ve elektriksel yalıtkanlığa sahip parçaların üretilmesini olanak sağlamıştır. Testlerden elde edilen sonuçlar otomotiv endüstrisinin beklentileriyle kıyaslanmış ve beklentilerden daha üstün özellikler elde edilmiştir.

Improvement of Environmentally-Friendly Alkyd Composite Coating with Graphene Oxide

In this article, environmentally-friendly alkyd coatings with different graphene oxide (GO) content of 0-1.5 weight percent (wt. %) were prepared for improving mechanical properties, corrosion protection and thermal oxidation resistance of coatings. GO in the coating was characterized by FT-IR. The corrosion resistance of environmentally- friendly alkyd coatings containing GO was investigated by salt fog testing. Effects of GO content on adhesion, flexural strength, relative hardness and thermal oxidation stability of alkyd coatings with and without GO were also examined. GO with the content of 1.2 wt. % significantly improved mechanical properties, corrosion resistance, thermal oxidation resistance of environmentally-friendly alkyd coatings.

Evaluation of corrosion protective properties of fly ash-red mud based geopolymer coating material for mild steel

Geopolymeric materials are fabricated via alkali activation of aluminosilicate materials by utilizing waste materials containing amorphous silica and alumina. Fly ash, red mud, metakaolin and blast furnace slag are the most common choices for the preparation of geopolymer. Among various well known applications of geopolymer, protective coating application has received increasing attention in recent years. The present work aimed to develop corrosion protective geopolymer coating for mild steel utilizing fly ash, red mud, alkali activators and additives. Coating material was prepared by addition of water and organic additives to nano sized geopolymer precursor which was prepared through solid state chemistry route. Developed coating was coated on cleaned and treated mild steel using spray coating technique. Coated plates were evaluated for adhesion strength, scratch test, impact test, water absorption and corrosion resistance by accelerated salt fog test as per ASTM/IS standards. Based on the results it is found that the developed coating material provides excellent corrosion protection and helps to enhance the service life of mild steel based structures.

Evaluation of Surface Degradation of Silicone Rubber by Continuous Salt-fog Aging Test

Evaluation of Surface Degradation of Silicone Rubber by Continuous Salt-fog Aging Test

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.

Stability Study of Materials for Electrode Supports for the Hydrogen Generation from a NaCl Aqueous Solution

The hydrogen generation by electrolysis from seawater is one of the most promising processes for this fuel production, avoiding the use of highly dangerous KOH solution as electrolyte. There are many problems associated with this process, such as the low electrochemical efficiency and the high corrosion capacity of chloride ions present in seawater. In this work, different materials proposed as possible electrodes or electrode supports in a NaCl solution are physicochemically analyzed from a comparative point of view. Corrosion studies by salt fog testing, Raman spectroscopy, X-ray diffractometry, and electrochemical analysis were carried out in this medium, and the catalytic efficiencies towards the electrochemical hydrogen generation were comparatively evaluated. Thus, samples of Ti, Ni, AISI 316L stainless steel, and Cu showed important hydrogen current in the analyzed potentials range. Their results recorded by cyclic voltammetry and electrochemical impedance spectroscopy, in addition to the Tafel plots, confirmed to be good active catalysts for hydrogen evolution reaction. On the other hand, materials as Al and carbon cloth show moderate and low corrosion in this medium and can be used as catalysts supports. It is found that nickel not only has a high tolerance to chloride ions but also presents the highest electrochemical efficiency. Its current density at −1.5 VSCE is 3.22 × 10–2 A cm−2, followed in order by AISI 316L stainless steel with high Ni content (1.33 × 10–2 A cm−2), concluding that Ni samples constitute the appropriate material for cathodes to be used in electrolyzers working with seawater.

Electrodeposited nickel–graphene nanocomposite coating: influence of graphene nanoplatelet size on wear and corrosion resistance

In this paper, we broaden our previous work, which investigated the influence of graphene nanoplatelets (GNPs) size on microstructure and hardness of composite coatings, to determine the effect of GNP size on wear-resistance and anti-corrosion property of GNP-reinforced nickel coating (Ni/GNPs). The experimental results indicated that the small GNP material size could enhance the wear resistance for nickel composite coating with the wear rate of 13.2 × 10–4 mm3/Nm, the wear depth of 17.69 µm. Meanwhile, the anti-corrosion property is enhanced significantly, this is shown via the low corrosion current density (Icorr value of 1.16 × 10–7 A/cm2) and the high corrosion potential (Ecorr value of − 0.1661 V). In addition, the mass lost in salt fog testing is low with the weight of 12.3 mg, which decreased down to ~ 55.27% compared to pristine Ni coating. These results are attributed to the uniform distribution of the small GNP size inside Ni matrix as well as the grain refinement effect of composite coating when using the small GNP size.

Multifaceted geopolymer coating: Material development, characterization and study of long term anti-corrosive properties

Abstract Geopolymers are traditionally used as construction and building material to partially replace Portland cement consumption. The versatile properties of geopolymer present it for use as a multifunctional material and geopolymer cementitious coating is an emerging part of it. In attempts to develop green and sustainable geopolymer coating material for advanced application, we studied geopolymeric coating of varying Na/Si ratio and alkaline molarities and their long term corrosion resistant properties on mild steel to protect it from surface corrosion. Chemical characterization was performed using combination of powerful characterization tools, more specifically mineralogical assessment by X-ray diffractometer, bonding arrangements by Fourier transform infrared spectroscopy and microstructural details by Field emission scanning electron microscopy techniques. Time of flight secondary ion mass spectroscopy was also used as novel characterization approach to envision the coating-substrate interface and for elemental mapping at the interface which delivered useful information about occurrence of strong covalent bonds between Si–O–Fe in the form of Fe2OSi+ mass fragment with m/z ratio 156. The material was further investigated in terms of adhesion strength and water/salt resistant, following accelerated salt fog test by ASTM codes. Geopolymer with varying Na/Si ratio and alkaline molarity exhibited change in XRD amorphicity and microstructure. Results also displayed that even at low Na/Si ratio geopolymeric coating performs high adhesion with iron with no considerable change in corrosion resistant properties. The maximum adhesion of developed material with mild steel was 14.68 M.Pa. after 28 day ambient curing which presented its functional suitability. Coating sustained point load upto 5 kgs and showed adequate water and salt resistance upto 3 months. In accelerated corrosion environment, optimized geopolymer coating displayed adequate corrosion resistance and displayed rust rating 9. Overall we obtained an optimized material which is well suited for coating of buried mild steel pipes to replace contemporary cement mortar coating in terms of properties, durability, cost effectiveness and environmental sustainability.

Uniform nucleation of zincate layer through the optimized etching process to prevent failure in electroless plating on 2024 aluminum alloy

Double zincate treatment is of considerable importance to provide a reliable interconnection between the aluminum surface and upper coatings. In this work, we focus on etching as a crucial step prior to zincating to demonstrate the critical importance of optimized etching parameters in the improved uniformity of the zincate layer and Ni-P deposit. The morphology study of the commercial aluminum alloy, which was coated through the conventional procedure of Ni plating and failed in the salt fog test, raveled many defects in the zincate layer and Ni deposit. It was hence assumed that the improper etching is responsible for an incomplete zincation and therefore. With this regard, in etching step, two different HF:HNO3 ratios (25:75 and 5:95 vol/vol) and four different immersion times (15, 30, 45 and 60 s) were applied, and optimum conditions for the growth of nanosize Zn layer with a uniform distribution on the overall surface of the substrate were found. The considerable influence of this surface modification on the formation of a uniform nickel-plated layer with fewer pinhole defects and better anticorrosive action was discussed. Besides, the reason for the failure of the used commercial alloy in the common etching process was explored in this paper.