Salt Water Immersion Test Research Articles

Bio-inspired and green fabrication of superhydrophobic materials with good robustness, stability and flame retardancy for oil-water separation based on waste cotton

Recently, more and more attention has been paid to bionic superhydrophobic materials for treating the intricate oil-water mixture system for the sake of resource recovery and environmental protection. With the in-depth development of research, scientists have been committed to pursuing the superhydrophobic materials via the economical, clean, and environmentally friendly methods. The current bio-inspired innovation of this paper concentrates on constructing superhydrophobic porous materials based on green, low-cost, and renewable waste cotton via in situ hydrothermal growth and solution immersion strategy. As anticipated, the water contact angle (WCA) of the prepared superhydrophobic cotton materials reaches 158°, exhibiting good self-cleaning ability and oil/water separation efficiency (99% ± 1%). Compared with pure cotton, superhydrophobic cotton materials also possesses elevated flame retardancy. In addition, after 300 cm abrasive paper friction tests, 10 times oil-water separation tests, 7 days of acid and alkali immersion tests (pH=1, 13), salt water immersion tests, and UV irradiation tests, as-prepared cotton materials can still maintain excellent superhydrophobic properties. On the basis of this work, an effective, facile and environmentally-benign avenue for fabricating the super-hydrophobic materials has been exploited that displays the promising applications in fields of waste cotton recycling, oil spill treatment and oil/water separation.

Evaluation of near-infrared spectroscopy as a contactless method for health monitoring of resin-based coating materials applied to concrete surfaces.

The surfaces of concrete structures are often coated with protective materials to minimize corrosion and weathering-based deterioration. Therefore, it is important to monitor the aging of the coating materials and their overall condition to extend the service lifetime of the structure effectively. Near-infrared spectroscopy (NIRS) is a contactless, nondestructive, rapid, and convenient method for material characterization; therefore, it is useful for onsite inspection of coating materials. Hence, in this study, we attempt to determine whether NIRS can be used for simple inspection for health monitoring of organic resin-based coating materials. In addition to identifying different severities of peeling damage, we characterize the ultraviolet-induced deterioration of coating materials with different thicknesses using diffuse reflection spectra acquired in the near-infrared wavelength region. For independent comparison with the NIR spectra, the state of the coating materials on the mortar specimens was analyzed using a combination of Fourier-transform infrared spectroscopy and scanning electron microscopy, while the state of the underlying mortar specimens was analyzed using permeability and salt-water immersion tests. The results confirm that the NIRS could detect the degradation of coating materials at early stages of deterioration before their permeability had been affected. NIRS offers the possibility of intermittent monitoring of coating deterioration. In addition, because the NIR spectrometer is portable, it can help in inspecting high-rise areas and areas that are difficult to reach. Therefore, we believe that NIRS is a simple, safe, and inexpensive method for inspection of surface coating materials.

Investigation of corrosion inhibitor used in cement

Steel bar corrosion inhibitor can be incorporated into concrete (or mortar) with a small amount, or coated on the cement surface to protect the steel materials. It can prevent or delay the corrosion of metal bars by directly acting on the steel bars in concrete (or mortar), but it does not affect the structure and properties of concrete. In this paper, the single component corrosion inhibitor was screened and evaluated at room temperature by salt water immersion test and static coupon weight loss method. The results show that hydrazine hydrate and KNO3 can effectively prevent the corrosion of reinforcement after being placed in simulated corrosion solution for 7 days. When the concentration of hydrazine hydrate and KNO3 is greater than 0.5%, the corrosion inhibition rate of KNO3 is 95.44% (100mg·L−1).

How does saltwater immersion affect the topographic, electrochemical and thermal characteristics of lithium-ion cells?

Given that many safety standards for lithium-ion cells include a saltwater immersion test and the possibility of cell immersion by water by accident, this work prepares five kinds of cells by varying immersion time and saltwater concentration to explore the influence of saltwater immersion on the topographic, electrochemical and thermal characteristics of cells. The exterior morphology of cells varies after immersion due to the corrosion of saltwater, and the severity worsens with the increase of immersion time and saltwater concentration. Besides that, saltwater immersion accelerates the degradation behavior of cells over cycling. Both electrode materials after immersion release less heat at elevated temperatures. The thermal runaway behavior is intensified if a cell is immersed in the 3.5% (wt.) saltwater for 2 h, while a more gentle thermal runaway behavior is illustrated if the immersion time lasts longer than 2 h or a saltwater with a higher concentration is used. Moreover, the thermal runaway propagation risk within modules after immersion is also significantly suppressed due to the decline of heat release. It is hoped that this research would aid in a better understanding of saltwater-immersed cells.

Water Absorption Behavior and Its Effect on Static Mechanical and Dynamic Mechanical Properties of Flax Fabric Reinforced Epoxy Composites

ABSTRACT In this work, four different grades of the Alkali cum Silane-treated plain-derived (irregular type) basket woven Flax fabric reinforced Epoxy (ASFE) composites were fabricated by varying their fiber weight fractions (0, 25, 35, and 45 wt.%) using compression molding technique. ASFE samples were subjected to salt water immersion test for 18 days and studied its effect on the their static and dynamic mechanical properties in accordance with ASTM standards. Also, interfacial shear strength between single flax fiber and epoxy material was determined using micro-droplet bonding test. Experimental Investigations revealed that salt water absorbed (SWA) flax/epoxy composites showed maximum drop of 23.23%, 29%, 35.43%, and 18.53% in tensile, flexural, impact and interlaminar shear strength, respectively. DMA study revealed that glass transition temperatures (Tg) of the ASFE composites were sensitive to the moisture absorption, and hence, SWA composites exhibited lower Tg value than dry composites. Furthermore, scanning electron microscopy clearly exposed fiber splitting, micro-cracks, and poor interfacial bonding of the ASFE composites.

Local galvanic corrosion analysis on cast Mg-Ca binary alloy using scanning Kelvin probe force microscopy

Mg2Ca precipitate effect on the local galvanic corrosion behavior of Mg-Ca alloy was quantitatively evaluated using the surface potential difference between Mg2Ca and α-Mg matrix measured by scanning Kelvin probe force microscopy. In a saltwater immersion test, discontinuous Mg2Ca precipitates acted as anodes and remarkably eroded rather than the matrix.

Understanding Corrosion Behavior of Magnesium Surface by x-Ray Irradiation for Improved Surface Design and Applications

An advanced surface modification processing design has been developed to improve the corrosion resistance of magnesium (Mg) samples via x-ray irradiation in humid air. OH· radicals generated by water ionization during x-ray irradiation reacted with natural oxide films mainly consisting of Mg(OH)2, which resulted in the formation of an approximately 50-nm-thick magnesium oxide (MgO) dense surface film as a protection layer against corrosion. After x-ray irradiation for 24 h, pure Mg and its alloy (AZ91D) specimens underwent the saltwater immersion test and exhibited a remarkable reduction in corrosion rate (80-85%). They were also compared to as-received samples after polishing treatment. This surface modification process is environmentally friendly because it does not release any hazardous materials because of the high recycling ability.

Ascorbic acid peptized alumina sol films with enhanced corrosion resistance performance

Alumina sol was prepared with ascorbic acid (also known as Vitamin C, Vc) as peptizer instead of the traditional used HCl. The prepared sol was then used for the anti-corrosion protection of NdFeB magnets. After substitution, the protective ability of the alumina sol film on NdFeB magnets improved significantly. Systematic comparison of the two alumina sol film were taken. Result showed that the Vc peptized alumina sol (AS-Vc) film showed a more uniform and complete surface which can help repair the defects on NdFeB surface without causing other damages. The electrochemical test showed the corrosion current density of NdFeB with AS-Vc film further reduced to 7.682 × 10−8 A cm-2, which is almost one-third of that in AS-Cl film. Along with the salt-water immersion test result, the data showed the corrosion is obviously suppressed after substitution. What’s more, the differences of the film formation mechanism between the two alumina films were investigated. By comparison, NdFeB in AS-Vc showed an about 200 mV more positive open circuit potential than it in HCl peptized alumina sol (AS-Cl), which means less redox reaction during the film formation process. Above all, the Vc peptized alumina sol provides higher corrosion resistance ability for NdFeB, which is wery suitable for the simple protection of NdFeB materials.

Effects of Oil Viscosity on the Anti-Corrosion and Self-Healing Properties of Oil-Impregnated Nanoporous Anodic Aluminum Oxide

Oil-impregnated nanoporous metal oxide surfaces such as anodic aluminum oxide showed significantly enhanced corrosion resistance and durability compared to hydrophilic or hydrophobic/superhydrophobic surfaces with no oil impregnation. Especially, the efficacy and durability of the oil-impregnated porous surfaces depend on the stability and retentivity of oil within the nanopores, where nanopores serve as reservoirs to hold the water-repelling and corrosion-protective oil in liquid phase. Previously, we demonstrated that the shape of nanopores should be an important factor to influence the stability and retention of oil. For example, it was demonstrated that the bottle-shaped nanopore featured with a smaller pore diameter at the upper layer than at the lower layer could immobilize the oil in the nanopores more stably than simply vertical nanopores, showing the greater corrosion resistance and robustness. In this study, we further report the effects of the oil viscosity on corrosion behaviors by testing bottle-shaped nanoporous anodic aluminum oxide surfaces impregnated with perfluorinated oils having various viscosities. Potentiodynamic polarization, salt fog and salt-water immersion tests show that the bottle-shaped nanoporous anodic aluminum oxide surfaces impregnated with more viscous oils result in the greater corrosion resistance and durability due to the enhanced oil retentivity. Despite the increased viscosity, the liquid oil still maintains the fluidity so that it fills physically damaged areas and allows the oil-impregnated surfaces to keep the self-healing capability. The result suggests that the anti-corrosion efficacy and durability of oil-impregnated porous surfaces can be optimized by modulating not only the pore geometry but also the oil viscosity.

Electrodeposition and Corrosion Resistance of Cu/Zn/Cu Multilayer Coatings

Cu/Zn/Cu multilayer coatings were prepared on mild steel substrates by dual bath technique in order to improve the corrosion resistance of mild steel in seawater. The microstructures of the coated substrates and its resistance to corrosion in simulated seawater were evaluated by scanning electron microscopy (SEM), the brine immersion test and electrochemical impedance spectroscopy (EIS). Salt water immersion test results show that the Cu/Zn/Cu multilayer coatings exhibited the highest corrosion resistance. The red rust spot appeared on the coating surface for the first time when the time of the coating soaked in salt water reached 2520h. The trend of the impedance variation reflected by the electrochemical impedance spectroscopy was the same as the change tendency of corrosion resistance was analyzed by the salt water immersion test. The results of SEM showed that the layer of copper were deposited by round cell structure, the middle layer of zinc coating was flat and compact.

Surface potential analysis on initial galvanic corrosion of Ti/Mg-Al dissimilar material

A surface potential analysis was carried out to establish a new materials design of pure Ti/Mg-Al alloy dissimilar materials with an excellent galvanic corrosion resistance. The formation of Ti-Al intermetallic interlayer and Al diffusion layer at interface effectively reduced the surface potential difference at the interface. As a result, a formation of local cells, causing a galvanic corrosion phenomenon of Ti/Mg alloy dissimilar material, was prevented because the potential difference of Mg alloy with Ti-Al interlayer completely decreased. A salt water immersion test obviously indicated no Mg(OH)2 corrosion product on Mg alloy surface due to Ti-Al interlayer formation, and the initial galvanic corrosion phenomenon was effectively obstructed.

바탕모르타르의 균열폭 및 도막방수재의 도포가 염화물이온 침투에 미치는 영향

The purpose of this study was to evaluate the salt damage resistance of waterproofing membrane in order to protect the mortar or concrete substrate. Polyurethane and acrylic coating membrane were used, and the salt water immersion test and the chloride ion concentration test were carried out experimentally. Also, the salt damage in mortar was analyzed by comparing with the permeability of each specimens. Waterproofing membrane have a high salt damage resistance more than only non-coated substrate, and prevented the penetration of chloride ion from non-crack to 0.3mm-crack specimens in 13 weeks-accelerating test. Finally, the membrane thickness for suppressing salt damage was estimated from viewpoint of its permeability.

Effects of Mg on morphologies and properties of hot dipped Zn–Mg coatings

This research aims to study the processing and the properties of hot-dipped Zn–Mg coatings with varying amount of Mg compositions. Zn–Mg coatings with 1wt.%, 2wt.%, 3wt.% and 4wt.% Mg were produced at 685°C using molten salt furnace with Argon protective gas atmosphere to minimise the oxidation of Mg. Characterisation techniques including X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) were performed to study the microstructures and phases of the coatings. The results showed that laminar eutectic containing MgZn2 and Zn formed at the grain boundary areas of Zn crystals in Zn–Mg coatings. Accelerated corrosion test methods like electrochemical and salt water immersion tests verified the improved anticorrosion properties of Zn–3wt.% Mg coating compared with pure Zn coating. A significant enhancement in the microhardness was also observed with the addition of Mg into the coating composition.

A study on corrosion behaviour of magnetron sputtered Zn–Mg coating deposited onto electro-galvanized steel

In this study, a nano-structured Zn–Mg coating was prepared by magnetron co-sputtering on electro-galvanized carbon steel. The microstructure and phase structure of Zn–Mg coating and its behaviour during saltwater immersion test were investigated by means of optical microscopy (OM), environmental scanning electron microscopy (ESEM), X-ray diffractometry (XRD) and electrochemical workstation. Electrochemical impedance spectroscopy (EIS) as a sensitive and reliable method was employed in corrosion mechanism research. The results show the formation process of a passive film on the surface of Zn–Mg coating during the immersion time range. The formation mechanism of this dense corrosion product Zn5(OH)8Cl2·H2O layer was also discussed. An electroplated Zn coating was also investigated for comparison purposes.

Effect of ceramics coating using sol–gel processing on corrosion resistance and age hardening of AZ80 magnesium alloy substrate

Extruded plates of AZ80 magnesium alloy were coated with CeO2 and/or MgO ceramics by sol–gel processing. We investigated the effects of heat treatment conditions, under which the ceramic thin film was formed, on the mechanical properties and corrosion resistance of the substrates. Single layer (CeO2 or MgO) and double layer (CeO2/MgO) ceramic thin films were successfully formed from precursor solution by the sol–gel processing under optimal heat treatment, in which the AZ80 original substrates were age-hardened. The corrosion resistance of AZ80 magnesium alloy substrates evaluated by the salt water immersion test was found to be improved by ceramic coating and microstructural change of the original substrate during coating process. The double layer ceramic coating was superior to the single layer coatings in terms of corrosion resistance. The acquisition of corrosion resistance in AZ80 magnesium alloy substrates could be applied simultaneously by sol–gel processing, while the substrates were age-hardened by the heat treatment.

Quantitative evaluation of initial galvanic corrosion behavior of CNTs reinforced Mg–Al alloy

The macroscopic corrosion phenomenon of the CNTs reinforced Mg composites remarkably occurred in the moist environment, due to a large potential of the galvanic cells formed between α-Mg matrix and CNTs. Therefore, it is necessary to reduce the potential difference at their interfaces in order to obstruct the galvanic corrosion phenomenon. In this study, AZ61B alloy composites reinforced with CNTs (CNT/AZ61B) were fabricated by powder metallurgy method, and their potential differences between CNTs and the α-Mg matrix were reduced by concentration of Al atoms around CNTs via heat treatment. The potential distribution around CNTs was measured by using scanning Kelvin probe force microscopy (SKPFM). Heat treatment of CNT/AZ61B composites at 823K for 10h caused the obvious concentration of Al atoms around CNTs, and resulted in the remarkable decrease of the potential difference at the interface between the α-Mg matrix and CNTs. Additionally, the salt water immersion test results indicated that the corrosion rate of CNTs/AZ61B composite materials after heat treatment was obviously reduced to less than about 30% of the non-treated composite material. Thus, the changes of α-Mg matrix potential by concentrating Al atoms around CNTs was effective to improve initial galvanic corrosion resistance of CNTs reinforced Mg composites.

Codeposited Zn–Mg coating with improved mechanical and anticorrosion properties

A Zn–Mg coating was prepared by magnetron co-sputtering method on carbon steel with Zn layer pre-deposited using an alkaline non-cyanide zinc bath. The morphologies, chemical compositions, mechanical properties and anticorrosion properties of specimens were investigated. The microhardness of the Zn–Mg coating increased from 244HV25 of the electroplated Zn coating to 323HV25. The electrochemical test in NaCl solution showed that the Zn–Mg coating had a passive region around the potential of 300mV. Salt water immersion test in 3.5wt.% NaCl solution also showed corrosion property improvement. The red rust generation time of Zn–Mg coating was doubled compared with the Zn coating. The possible mechanism of the improvement of corrosion resistance of Zn–Mg coating is proposed.

Surface Modification Phenomenon of X-ray Irradiated Pure Mg

Magnesium (Mg) and it alloys are highly corrosive due to their low standard electrode potential (SEP). The conventional methods to improve corrosion resistance of Mg alloys are anodic oxide film formation and chemical conversion treatment. However, these methods are expensive and also make it hard to recycle the Mg products with these treatments. In this study, unique oxide layer formed by radical reaction between pure Mg surface and radical species generated under X-ray irradiation was investigated. Pure Mg surface was modified by X-ray irradiation under atmospheric condition. XPS analysis indicated MgO layer was formed at the surface of X-ray irradiated pure Mg specimen. Cross-sectional observation by TEM showed the MgO layer was dense compared to the natural oxidation coating films. The thickness of surface modification layer by X-ray irradiation was increased with the increase of irradiation time. After salt water immersion test, X-ray irradiated pure Mg for 24 hours showed about four times corrosion resistance of the as-polished original pure Mg. These results suggest that dense MgO layer formed by X-ray irradiation on pure Mg surface were functioning as a protective film.

탄소섬유/에폭시 복합재의 기계적 특성에 미치는 염수환경의 열습 영향

본 연구에서는 최대 12개월 동안 염수침수시험을 수행하여 염수환경의 열습조건이 복합재의 특성에 미치는 영향을 조사하였다. 복합재 시편은 직물 형태의 탄소섬유와 에폭시로 구성된 프리프레그를 적층하여 제작하였으며, 노출온도 35℃, 55℃, 75℃가 적용된 염수환경에 완전 침수시키는 조건을 적용하였다. 연구결과에 따르면 복합재의 인장강성과 인장강도는 노출온도와 노출시간이 증가할수록 노출 전에 비해 감소 정도가 크지 않았지만 이에 비해 압축강성과 압축강도는 감소 정도가 크게 나타났다. 특히 압축강도는 노출온도가 증가할수록 염수침투가 가속화되어 감소 정도가 크게 나타났다.<BR>

An In-Situ Phosphating Coating Catalyzed by Phenylphosphonic Acid on AA6061

In order to solve the problems of that exist in traditional multi-stage phosphating process (such as error-prone operation, cost and waste), a novel in-situ phosphating coating (ISPC) system was developed. This was achieved by predispersing an optimum amount of in-situ phosphating reagent (ISPR) into the paint formulation. The corrosion protection performance of the ISPC comprised of alkyd ready-mixed paint catalyzed by phenylphosphonic acid (PPA) as in-situ phosphating reagent (ISPR) was investigated using electrochemical measurement and salt water immersion (SWI) test. The results indicated that adding 2% phenylphosphonic acid in alkyd ready mixed paint system can obviously improve the corrosion protection performance of the paint coating cured at 50°C for 8h.