Immersion In NaCl Solution Research Articles

Self-healing solid slippery surface with porous structure and enhanced corrosion resistance

• A solid slippery surface was successfully fabricated via a facile method. • The slippery surface showed good chemical and mechanical stability. • The slippery surface showed superior corrosion resistance and self-healing property. The corrosion issue of metals is common and has significant impact on social development. In recent decades, the novel slippery surface (lubricant infused surface) inspired by “Nepenthes pitcher plant” has attracted extensive attentions for corrosion protection on account of its superior water repellency. However, most of the construction process for slippery surface was complex and the lubricant was easy to be dissipated in air or liquid environment. In this work, a facile hydrogen bubble dynamic template method (HBTM) was applied to construct porous structure, and the stable phase-change material paraffin was then infused into the porous structure for solid slippery surface. The results showed that the morphology of obtained sample constructed at 3 A·cm −2 exhibited a homogeneously porous structure. In addition, the slippery surface could be self-healing with thermally assistant after mechanical abrasion. More importantly, the slippery surface showed excellent anti-corrosion performance with a corrosion current density of 1.138 × 10 −7 A cm −2 . It was worth mentioning that the corrosion resistance of the slippery surface was still very good even after immersion in NaCl solution for 3 weeks. The fourier transform infrared spectroscopy and ultraviolet results revealed that the dissolution of paraffin in NaCl solution can be neglected, indicating an excellent stability. Thus, the facile method has great significance for guiding the fabrication of slippery surface and we envision that the solid slippery surface can effectively protect metal materials from corrosion.

Simulation of steel rod atmospheric corrosion by alternate immersion in salt solution

Corroded B235 reinforcing steel rods, which were exposed to an open air environment for 25 years, with a certain specific mass loss, were studied. Test pieces were prepared from them by lathe machining. The test pieces were subjected to accelerated corrosion through an alternate immersion in NaCl solution. The same specific mass loss as on the initial corroded rods was achieved for 52 days. Further the test pieces were cleaned, observed, photographed and tensile tested. The cleaned surfaces and the stress-strain curves of the test pieces were compared with results, obtained from the initial corroded rods. It was found out about the tested steel rods that alternate immersion in salt solution for 52 days is a good simulation of twenty-five-year atmospheric corrosion.

(Invited) The Subsurface Structure of Abraded Al-Zn-Mg-Cu Alloy and Its Effects on Corrosion

Surface abrasion, sometimes followed by polishing, can create an altered surface layer (ASL) with thickness of a few hundreds of nanometers, which has different microstructure than the underlying bulk. Such an ASL typically contains ultrafine subgrains, and second phase particles that result from unusual phase transformations. ASLs have been shown to exhibit a different corrosion resistance than the underlying matrix, and can be either more susceptible or more resistant to corrosion. In this work, the ASL microstructure of AA7055 was studied at the early stages of natural aging right after surface abrasion using transmission electron microscopy (TEM) and atom probe tomography (APT). For the as-abraded ASL, the pre-existing η′/η precipitates and grain boundaries were deformed and aligned along the abrasion direction. However, for the abraded and 7-day natural aged bulk sample, ultrafine subgrains formed in the localized region of the ASL, and MgxZny and Al2Cu particles precipitated at the subgrain boundaries. To accelerate the precipitate kinetics of the ASL, the bulk abraded sample was heated at 50 oC for 1 h; more subgrains and Al2Cu particles formed in the whole ASL. Potentiodynamic polarization testing was performed on the abraded and aged bulk samples during immersion in NaCl solution. With increasing post-aging temperature and time, the breakdown potential of the ASL increased. Acknowledgements: focus ion beam and TEM were conducted at Center for Electron Microscopy and Analysis at The Ohio State University. APT was conducted at Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, which is a U.S. DOE Office of Science User Facility.

Bio-based polybenzoxazine superhydrophobic coating with active corrosion resistance for carbon steel protection

A bio-based benzoxazine, synthesized from cardanol, stearylamine and paraformaldehyde, was utilized to develop a superhydrophobic polybenzoxazine double-layer coating with active protection for carbon steel. This double-layered coating consists of an active anti-corrosive primer and a superhydrophobic topcoat. Halloysite nanocontainers with 2-mercaptobenzimidazole were embedded in the primer to achieve active corrosion resistance. The superhydrophobic topcoat constructed of low-surface-energy polybenzoxazine and amine-modified silica nanoparticles can acquire reinforced passive anticorrosive barrier. The durable double-layer coating could still maintain its superhydrophobicity, even after 60 days of treatment at −20 °C or 100 °C, or 100 cycles of sandpaper abrasion. More importantly, the electrochemical measurement results indicated that the polybenzoxazine superhydrophobic coating maintained outstanding anti-corrosion performance during 90 days immersion in NaCl solution.

Enhancement of corrosion resistance of AZ31 Mg alloys by one-step in situ synthesis of ZnAl-LDH films intercalated with organic anions (ASP, La)

Inserting corrosion inhibitors into a lamellar protective coating is an effective way to improve the corrosion resistance of metal substrates. In this work, two kinds of environmentally friendly organic acid anions, aspartic acid (ASP) and lauric acid (La), were explored as corrosion inhibitors to in situ intercalate into the ZnAl-layered double hydroxides (ZnAl-LDHs) on AZ31 magnesium alloys by a facile one-step hydrothermal method. The morphology, composition, structure and the corrosion resistance of these two LDHs coating before and after corrosion experiment were investigated. It is found that both the two kinds of ZnAl-LDHs films consist of uniform and dense layered nanosheets (NSs), and the NSs of ZnAl-ASP-LDHs films grow vertically, but those of ZnAl-La-LDHs films exhibit a staggered tilted structure. The corrosion current density of the two ZnAl-LDHs films are two orders of magnitude lower than that of Mg alloy substrate. After one week's immersion in NaCl solution, the NSs structure of two kind of ZnAl-LDHs films still remains the uniform and densely coverage on Mg alloy. Owing to the larger d (003) spacing, the ZnAl-La-LDHs have better ability to absorb Cl − and release interlayer anions than ZnAl-ASP-LDHs. These results indicate that the ZnAl-LDHs films intercalated with organic anions, specially La anions, can significantly improve the corrosion resistance of Mg alloy.

Influence of steel fibers corroded through multiple microcracks on the tensile behavior of ultra-high-performance concrete

This study aims to investigate the effects of pre-formed microcrack properties and immersion duration in a 3.5% NaCl solution on the corrosion degree of steel fibers in ultra-high-performance concrete (UHPC). Two types of steel fiber, i.e., straight and twisted, two pre-strain levels causing different microcrack properties, i.e., 0.45% and 0.6%, and four immersion durations of 0, 4, 10, and 20 weeks were investigated. Energy-dispersive X-ray spectroscopy (EDX) analysis was conducted using scanning electron microscope images for a quantitative evaluation of the degree of surface corrosion. Test results indicated that steel fibers embedded in the multi-cracked UHPC are oxidized due to permeation of the NaCl solution and longer immersion durations lead to a higher corrosion degree in general. Better tensile performance was achieved if both the straight and twisted steel fibers were moderately corroded. The twisted-fiber-reinforced UHPC was more susceptible to corrosion than the straight-fiber-reinforced UHPC, indicated by the earlier deterioration in tensile performance and lower tensile parameter ratios. Given identical immersion durations, the composites with fewer and smaller microcracks provided better tensile performance due to the moderately corroded steel fibers. Steel fiber corrosion influences the energy absorption capacity more significantly than the tensile strength, irrespective of the fiber type and microcrack property.

Rapid synthesis of scaly SiO2 coating on flake carbonyl iron powders by plasma electrolysis

The scaly SiO2 coating was rapidly synthesized on the flake carbonyl iron powders by plasma electrolysis to solve the poor corrosion resistance. The effect of the processing numbers on the microstructure and corrosion resistance was systematically investigated. A fully covered and dense thin film was formed, excepted for the processing number of two and three times, where several typically smooth uncoated flake particles were observed. The corrosion test during immersion in NaCl solution for 60 days evidenced the greatly improved corrosion resistance with the one-time powders showed the best. The initial oxidation temperatures of the coated powders were increased by 50–85 °C with the one-time best, again revealing the effective protection of the film. The formation mechanism was also discussed mainly based on the electrochemical process and the plasma effects. We believe the plasma electrolysis will find a wide range of applications in the surface modification of metal powders.

The effect of graphene nanoplatelets on the flexural properties of fiber metal laminates under marine environmental conditions

In this research, the effects of adding graphene nanoplatelets (GNPs) on the flexural properties of fiber metal laminates (FMLs) under marine environmental conditions were investigated. The FMLs were fabricated with alternating layers of Al6061 and glass fiber reinforced epoxy (GFRE) with different concentrations of GNPs (0.25, 0.5, and 1.0 wt%). The samples were immersed in the 3.5 wt% NaCl solution for different immersion times (7, 14, and 28 days) at room temperature. The addition of GNPs led to decreasing the water absorption of samples after immersion in the 3.5 wt% NaCl solution; the lowest absorbed water was for the samples with 0.25 wt% GNPs. Although the flexural properties of samples decreased by increasing the immersion time, the lowest reduction in flexural properties was obtained for the sample with 0.25 wt% GNPs. Results showed that by adding GNPs and immersing the specimens in the 3.5 wt% NaCl solution for 28 days, the flexural strength and modulus, and strain values of specimens containing 0.25 wt% GNPs were respectively about 128%, 63%, and 1.85 times higher than those of samples without GNPs. Also, the reduction of the flexural properties caused by immersion in NaCl solution was lower than that of samples without GNPs. Moreover, the water uptake of samples with 0.25, 0.5, and 1.0 wt% GNPs was about 38%, 31%, and 37% lower than that of samples without GNPs after 28 days of immersion. Microstructural analyses revealed that the improvements in the metal/polymer adhesion and mechanical properties of the polymeric part of FMLs resulting from various mechanisms were the main reasons for the improved performance of samples with GNPs under marine conditions.

Durability of seawater and sea sand concrete and seawater and sea sand concrete–filled fibre-reinforced polymer/stainless steel tubular stub columns

This article presents an experimental investigation on the durability behaviour of seawater sea sand concrete and seawater sea sand concrete–filled fibre-reinforced polymer/stainless steel tubular stub columns. Effects of NaCl of seawater on the strength of seawater sea sand concrete and on the deterioration of fibre-reinforced polymer were studied. Accelerated degradation tests were conducted on fibre-reinforced polymer rings exposed to a combined environment of 3.5% NaCl solution and seawater sea sand concrete. Obvious hoop strength reductions were observed in glass fibre-reinforced polymer and basalt fibre-reinforced polymer rings after 6-month exposure at 60°C. Seawater sea sand concrete–filled glass fibre-reinforced polymer tubular stub columns were exposed to an indoor environment (i.e. aged in air at room temperature) for a maximum duration of 2.5 years and no degradation was found by comparing the axial compressive test results from unexposed and exposed specimens. Seawater sea sand concrete–filled stainless steel tubes did not show any deterioration in strength after a 2.5-year exposure to an indoor environment or a 1.5-year immersion in NaCl solution. This study indicated that a hydrothermal environment (e.g. full immersion in solution) is much more aggressive to fibre-reinforced polymer than a dry environment. The reliability of using accelerated degradation test data to estimate the long-term performance of fibre-reinforced polymer–related structures in a real environment may need further research.

The enhanced properties of anodic films on AZ91D magnesium alloy by addition of oxide nanoparticles

Anodic films are prepared on AZ91D magnesium alloy in the electrolytes with Al2O3、SiC、TiO2、ZrO2 and CeO2 nanoparticles respectively. The oxide nanoparticles are partly embedded in the anodic films during the oxidation process. The film porosity decreases with the addition of oxide nanoparticles. As the film porosity increases, the film microhardness decreases while the bonding strength increases, and the microhardness of the anodic film prepared with SiC nanoparticles is as high as 900.7 HV. The increased interpore distance and the decreased film porosity could decrease the thermal cracking tendency of the anodic films. Particularly, the anodic film prepared with CeO2 nanoparticles does not crack after heating. The crack density increases more quickly than the crack width with the changed pore parameters. After 1200 h immersion in NaCl solution the resistance values of the anodic films prepared in the electrolytes with SiC、TiO2、ZrO2 and CeO2 nanoparticles are still higher than 105 Ω cm2, two orders of magnitude higher than the values of the films prepared with Al2O3 and without oxide nanoparticles, and the film capacity increases very slowly. The anodic film prepared with ZrO2 nanoparticles shows the best corrosion resistance. The better corrosion resistance of the anodic films is attributed to the oxide nanoparticles filling the defect position, changing the film composition and improving the film defect structure.

Improvement of Corrosion Resistance and Solid Content of Zinc Phosphate Pigmented Alkyd Coating by Methacrylated Cardanol

Two cardanol (CO) derivatives, methacrylated cardanol (MACO) and triethoxysilane functionalized cardanol (TSCO) were investigated as the reactive diluents for a zinc phosphate pigmented alkyd coating. It was found that 5 wt% of MACO or TSCO can reduce the dosage of xylene by ∼ 3 wt% while maintaining the viscosity of the alkyd coating system. TSCO presented a negative influence on the drying time and the pull-off adhesion strength of the alkyd coating; however, the addition of 15 wt% MACO decreased the drying time from 12 h to 8 h and increased the pull-off adhesion strength from ∼ 1.73 to ∼ 2.10 MPa, comparing with the neat alkyd coating (without MACO and TSCO). As evidenced by the salt spray test, the addition of TSCO did not show an enhancement of corrosion resistance for the alkyd coating; however, the alkyd coating containing 15 wt% MACO (labelled as M-15) presented superior corrosion resistance to other coating systems. M-15 and the neat alkyd coating were further characterized by electrochemical impedance spectroscopy (EIS). The results of EIS further demonstrated that the corrosion resistance of M-15 is much better than the neat alkyd coating in the 3.5 wt% NaCl solution immersion. Importantly, M-15 can provide an excellent protection of the steel in the corrosive immersion condition for at least 123 days. The improvement of the overall performance was attributed to the homo-polymerization of the methacrylate moiety in MACO. Taken these results together, MACO is an efficient chemical for formulating high solid alkyd coatings with outstanding corrosion resistance.

Electrochemical Behavior and Self-Sealing Ability of Zirconium Conversion Coating Applied on Aluminum Alloy 3005 in 0.5 M NaCl Solution

Zirconium conversion coating (ZrCC) was prepared on aluminum-manganese alloy AA3005 by immersion in 200 ppm of H2ZrF6 bath for 10 min at room temperature. Potentiodynamic polarization curves and electrochemical impedance spectra were measured up to 10 and 40 days, respectively, in 0.5 M NaCl solution. Microstructural characterization of samples was carried out using scanning electron microscopy equipped with energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, focus ion beam microscopy and transmission electron microscopy. The coating had a tri-layer structure with a thickness of 200 nm in the proximity of intermetallic particles and 30 nm far from intermetallic particles at the coating matrix. Electrochemical measurements showed that the corrosion resistance of ZrCC on AA3005 was improving during immersion in NaCl solution, i.e., impedance value at low frequency increased with immersion time reaching the average value 8.5 ∙ 106 Ω∙cm2 at 3 mHz after 10 days immersion. Microstructural and compositional characterization showed that this behavior is related to the change in composition and structure of conversion coating including a transformation of ZrF4/ZrOxFy to ZrO2 · 2H2O(s) and formation of Al(OH)3 in the top layer of ZrCC, respectively, accompanied by the change in thickness of individual layers within the coating.

Experimental study of corrosion rate on st60 steel as a result of immersion in HCl, NaOH, and NaCl solutions

The purpose of this study is to calculate corrosion rate (CR) of ST60 steel. A wet corrosion test was conducted by dipping ST60 steel in the solution of HCl, NaOH, NaCl. Use weight loss Method to calculate CR. It was found that the highest corrosion rate occured when the specimen of ST60 steel dipped on HCl0.1M solution. Corrosion that occurs for all corrosion tests is immersion in HCl, NaOH, and NaCl solutions produces uniform corrosion

Enhanced corrosion protection by Al surface immobilization of in-situ grown layered double hydroxide films co-intercalated with inhibitors and low surface energy species

In this work, a novel in-situ grown layered double hydroxide (LDH) film co-intercalated with inhibitors (vanadates) and low surface energy substance (laurates) was immobilized on Al substrates. A long-term monitoring of electrochemical impedance spectra (EIS) of the various samples in 3.5 wt.% NaCl solution demonstrated the synergetic protection of the intercalated two functional species. Meanwhile, the X-ray diffraction (XRD) result of the samples after immersion in NaCl solution for a long time presented the anion-exchange process between vanadates/laurates and chlorides. The synergetic effect of the two species loaded film significantly contributed to the enhanced long-term corrosion protection of aluminum.

The pore structure and properties of microarc oxidation films on 2024 aluminum alloy prepared in electrolytes with oxide nanoparticles

Microarc oxidation films on 2024 aluminium alloy were prepared in sodium silicate-based electrolyte with α-Al2O3, SiC, TiO2, ZrO2 and CeO2 nanoparticles. The effects of oxide nanoparticles on the pore parameters and the properties of the films were studied. EDS and XRD analysis showed that the nanoparticles partly entered the film, probably by the combination effects of embedding and melting. The porosity of the microarc oxidation films prepared in electrolytes with nanoparticles increased to some extent. With the addition of the different nanoparticles, the film porosity increased from 9.6% to 21.6%, the bonding strength of the films to the adhesives increased from 12.3 MPa to 22.8 MPa, and the film microhardness decreased from 785.7 HV to 564.2 HV. Particularly, the microhardness of the film prepared with SiC nanoparticles was as high as 1063.5 HV. The addition of all the nanoparticles into the electrolytes did not affect the thermal cracking resistance of the films. EIS measurements showed that after 1440 h immersion in NaCl solution the resistance of the microarc oxidation films prepared in electrolyte with nanoparticles was still much higher than that of the original film, and the film capacity increased slowly. Among the nanoparticles, TiO2 and CeO2 showed the best effect to increase the corrosion resistance. Weight loss test results showed that the corrosion rate of the films prepared with TiO2 and CeO2 nanoparticles was only about one third of the original film after 8640 h immersion. The good corrosion resistance of the microarc oxidation films may depend mainly on the good shielding property of the inner compact layer.

Chloride diffusion of shotcrete lining structure subjected to nitric acid, salt–frost degradation, and bending stress in marine environment

The chloride diffusion of shotcrete lining at the middle and passageway of submarine tunnels subjected to chloride attack, combined action of NxOy from automobile exhaust and chloride attack, salt–frost degradation, and surrounding rock stress was investigated using 3.5%NaCl and HNO3+3.5%NaCl solution immersion method, accelerated salt–freezing-thawing method, and spring four-point bending loads method, respectively. Chloride content in shotcrete was measured using solid–liquid extraction and potential method. Meanwhile, the influence of chloride diffusion on nitric acid attack, salt–frost deterioration, bending stress, and shotcrete mixture parameters were analyzed. Nitric acid attack, salt–frost degradation and bending stress accelerated chloride migrate into shotcrete. When immersed in NaCl and HNO3+NaCl solution, shotcrete with low water–binder ratio and high steel fiber content had lower chloride content. With the increase in fly ash replacement, the chloride content decreased initially and then increased rapidly. Under salt–frost degradation, the shotcrete with low water–binder ratio and fly ash replacement had better chloride diffusion resistance. The distribution of chloride content in concrete conformed to Fick's second law. The chloride diffusion model was established based on the temperature of environmental and humidity of concrete, exposure time to solution, mixture parameters of shotcrete, nitric acid attack, salt–frost degradation, and bending stress.

Superhydrophobic nickel coatings fabricated by scanning electrodeposition on stainless steel formed by selective laser melting

In this paper, a simple, flexible method to fabricate the superhydrophobic nickel coatings by scanning electrodeposition was proposed. By changing the parameter of current densities, the morphology, microstructure, chemical composition, wettability, and stability of the samples were studied. The results showed that the clusters with hierarchical structures and the chemical composition were important in the formation of super-hydrophobic surface. The fresh coatings were hydrophilic. After placed in air for a week, the contact angles were varied from super-hydrophobic (contact angle 152.3°) to relatively hydrophobic (contact angle 112.6°) by controlling the parameter of current densities. The mechanisms of hydrophobic and forming were illustrated. Moreover, the super-hydrophobic coating possesses excellent stability and corrosion resistance, and it still maintains the corrosion protection after immersion in NaCl solution for a week.

Effect of minor Ge addition on microstructure and localized corrosion behavior of Al-Zn-Mg alloy sheet

The effect of minor Ge addition on microstructure and localized corrosion behavior of Al-Zn-Mg alloy sheet was investigated. Ge leads to the formation of Mg2Ge phase, which can stimulate recrystallization nucleus, and a higher density of smaller Al3Zr dispersoids, which can inhibit recrystallization effectively. Consequently, a lower recrystallization fraction and smaller recrystallized grains are obtained in the Ge-added sheet. Ge reduces the density of η′ strengthening precipitates in the interior of grains but increase the length and spacing of η precipitates at grain boundaries. The corrosion potential is similar for Mg2Ge phase and the matrix, and therefore Mg2Ge phase and the matrix around it do not dissolve during immersion in NaCl solution. Corrosion immersion test and electrochemical test results show that Ge can improve exfoliation corrosion resistance. The reason has been discussed based on the modification of microstructure caused by Ge addition.

1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP)-Zn complex thin films for the corrosion protection of cold-rolled steel (CRS)

Self-strengthening HEDP-Zn films were constructed on the CRS surface and the corrosion protection was afforded by electrochemical impedance spectroscopy (EIS) tests. After immersion in NaCl solution, HEDP-Zn-coated CRS underwent three stages: strengthening, balance and weakening. During immersion, a portion of unstable HEDP-Zn complexes were destroyed, accompanied by the intercalation and departure of Na+, thereby resulting in the changes in microstructure, chemical compositions and thickness of the films. Thus, anticorrosion performance increased due to the increased surface coverage by the complexes and additional binding sites during the first stage but decreased because of the reduced film thickness in the third stage.

Enhancement of the active/passive anti-corrosion properties of epoxy coating via inclusion of histamine/zinc modified/reduced graphene oxide nanosheets

Abstract This research introduces a green/novel route for preparation of an epoxy system with bi-functional active/passive anti-corrosion properties via inclusion of modified/reduced graphene nanoparticles. For the first time, the reduced nanosheet (RGO) with the barrier-inhibitive activities was prepared using bioactive reductant based on histamine. Also, zinc cations were loaded onto RGO sheets by two sequence based (RGO-Hist-Zn-I nanosheet) and in-situ based (RGO-Hist-Zn-II nanosheet) approaches. Characterization of the synthesized RGOs using X-ray photoelectron spectroscopy, field emission-scanning electron microscopy, transmittance electron microscopy, ultraviolet-visible and inductively coupled plasma techniques approved the precision of graphene oxide reduction via histamine and zinc cation's chemical adsorption. The performance of the RGO nanosheets was investigated by electrochemical impedance spectroscopy, potentiodynamic polarization, salt spray, pull off adhesion, cathodic disbondment (CD) and energy dispersive X-ray spectroscopy analyses. The results clarified that the epoxy coating reinforced with RGO-Hist-Zn-I provided the best anti-corrosion performance (log |Z|10 mHz = 9.73 Ω cm2 after 60 days immersion in NaCl solution), self-healing property (liberation of histamine and zinc cations from the nanocomposite bulk to the scratch region after 8 h immersion), adhesion to steel surface (lowest adhesion loss, i.e. 14.2% after 38 days of immersion and CD resistance (ca. 4.7 mm).