Alloys In Seawater Research Articles

Refreshable self-polishing superhydrophobic coating on Mg alloy to prohibit corrosion and biofouling in marine environment

Corrosion susceptibility is a critical obstacle for Mg alloy usage in harsh environments. Bioinspired superhydrophobic surface (SHS) affords a new way to combat corrosion. However, problems, e.g., water vapor condensation and air dissolution, ceaselessly hurdle practical usage of SHS for long-term corrosion inhibition. In this report, targeting the corrosion inhibition of Mg alloy in seawater, a refreshable self-polishing superhydrophobic coating is bound onto AZ31 Mg alloy bridging via a ceramic/paraffin buffer layer to solve the two problems encountered by traditional SHS. Firstly, the liquid paraffin is injected into the porous ceramic structure constructed by micro-arc oxidation (MAO). Then, carbon soot (CS) is grown onto the ceramic/paraffin layer via a combustion method. The internal CS layer is firmly bonded due to the molten paraffin. Meanwhile, the external superhydrophobic CS layer is soft and floppy to perform self-polishing property under dynamic water flow condition. The refreshable feature endows the regeneration of SHS. Using water jet flush (5.8 m/s) and immersion test up to 168 h, Mg alloy covered ceramic layer and carbon soot (MMAO-CS) coating demonstrates excellent stability. Using diatoms as target organisms to illustrate seawater anti-biofouling property, a few diatoms are found on MMAO-CS even after immersion for 10 d due to the low modulus and self-polishing of the external superhydrophobic layer invaded by the water phase and bio-organisms. For prohibiting corrosion in seawater environment, MMAO-CS coating possesses prominent resistance with |Z|0.01 Hz (2.82 ×107 Ω cm2) of 6 orders of magnitude larger than bare AZ31 (42.9 Ω cm2), enabling its potential usage in marine environment.

Seawater Corrosion of Copper and Its Alloy Coated with Hydrothermal Carbon

Nonferrous materials such as copper and its alloys are sensitive to seawater corrosion. In this work, a hydrothermal carbonization coating was deposited on a C26000 brass and pure copper. The effectiveness of the coating on improving seawater corrosion performance was examined. First, hydrothermal carbonization of sugar (with 10 wt.% sucrose in water) at 200 °C and 1.35 MPa for 4 h was performed to generate the carbon-rich coating. The results of surface morphology, composition, hardness, thickness, and wettability to seawater were presented. Then, the corrosion resistance of the brass and pure copper with and without coating was evaluated by measuring the Tafel constants in seawater. Important parameters including the corrosion current, potentials of corrosion, and polarization resistance for the brass and pure copper with and without the coating were calculated from the polarization measurement data. It was found that the hydrothermal carbonization of sugar produced a relatively dense carbon-rich layer on the surface of the copper and brass specimens. This carbon layer has a thickness of 120 µm, and it is highly corrosion resistant. The corrosion current of the copper and its alloy in seawater is reduced significantly through the hydrothermal carbonization treatment. The carbonized coating reduced the corrosion current obviously, but only resulted in a small positive shift of 0.05–0.1 V in the corrosion potentials. The hydrothermally produced carbon layer is just like a passivation coating on the pure copper and copper alloy to slow down their corrosion rates in seawater.

Microstructure, Mechanical and Tribological Properties of Si3N4/Mo-Laminated Composites.

(1) Background: the applications of ceramic materials in a friction pair and a moving pair are limited, just because of their poor toughness and unsatisfactory tribological characteristics. In view of this, Mo as a soft metal layer was added into a Si3N4 matrix to improve its toughness and tribological characteristics. (2) Methods: The microstructure and metal/ceramic transition layer were examined using X-ray diffraction, scanning electron microscope, electron dispersive X-ray spectroscopy, and Vickers hardness. Bending strength and fracture toughness were also measured. Tribological characteristics were obtained on the pin-on-disc wear tester. (3) Results: It can be found that the multilayer structure could improve the fracture toughness of laminated composite compared with single-phase Si3N4, but the bending strength was significantly reduced. Through microstructure observation, the transition layer of Si3N4/Mo-laminated composite was revealed as follows: Si3N4→MoSi2→Mo5Si3→Mo3Si→Mo. Moreover, the addition of the Mo interface to silicon nitride ceramic could not significantly improve the tribological properties of Si3N4 ceramic against titanium alloy in seawater, and the friction coefficients and wear rates of the sliding pairs increased with the increase in load. (4) Conclusions: The process failed to simultaneously improve the comprehensive mechanical properties and tribological performance of Si3N4 ceramic by adding Mo as the soft interfacial layer. However, the utilization of metal interfacial layers to enhance the toughness of ceramics was further recognized and has potential significance for the optimization of ceramic formulation.

Predicting the corrosion properties of cast and hot isostatic pressed CoCrMo/W alloys in seawater by machine learning

PurposeCobalt-based alloys exhibit a unique combination of wear resistance, strength and corrosion resistance. Localized corrosion of such alloys in seawater system can be several orders of magnitude faster than general corrosion, and direct experimental evidence of the local activation process is still lacking, which makes the accurate prediction for properties difficult, especially for long-term corrosion. The purpose of this study is revealing the relationship between multiple environments and corrosion properties to predict the corrosion of cobalt-based alloys.Design/methodology/approachA data-driven method for the prediction of the corrosion behavior of cast and hot isostatic-pressed CoCrMo/W alloys in seawater is proposed. The gradient boosting regression models calculate mean relative errors (MREs) of 0.160 and 0.435 by evaluating a hold-out set for breakdown potential (Eb) and maximum current density (imax), respectively, considering various compositions, synthesis methods and corrosion environments.FindingsThe models can be used to estimate the “unseen” cobalt-based alloy after immersion in 3.5 Wt.% NaCl solution for one, two, four and eight months to obtain high precision with MREs of 7.8% and 9.8% for Eb and imax, respectively.Originality/valueMachine learning method provides novel and promising insights for the prediction of localized corrosion properties.

The corrosion resistance of porous Ni–Ti alloys in seawater

Porous Ni–Ti alloys were fabricated by reactive synthesis of Ni and Ti elemental powders. The corrosion behavior of porous Ni–Ti alloys was explored by electrochemical methods and weight change measurements at 298 K in seawater. The polarization curves and electrochemical impedance spectroscopy data show that porous Ni–Ti (6.5:3.5) alloys provide the best corrosion resistance. The values of corrosion current density and corrosion rate are 1.6944 × 10−4 mA/cm2 and 1.9929 mm/a, respectively. The corrosion behavior and corrosion mechanism of porous Ni–Ti alloys are also discussed.

The enhancement of individual friction and corrosion properties of CrSiN coatings by Mo doping in seawater

A series of CrSiN coating with various Mo contents were fabricated on Ti6Al4V alloys using a closed unbalanced magnetron sputtering system and their tribological and electrochemical behaviors were investigated. The results of friction tests suggested that oxidation behaviors of Mo element in the prepared coatings promoted the wear mechanism transforming to tribochemical wear, and the more Mo doping enhanced the tribological performance and presented the lowest wear rates of 2.27 × 10 −7 mm 3 /N.m and 8.12 × 10 −8 mm 3 /N.m for tribopairs of Cr( Mo )SiN/Al 2 O 3 and Cr( Mo )SiN/Si 3 N 4 , respectively. Besides, the corrosion product of MoO 3 reduced the corrosion rate of CrMoSiN coatings, CrMoSiN coating showed the low corrosion rate of 0.58 × 10 −3 mm/yr indicated that the passive behaviors of Mo element improved the corrosion resistance, and provided a good protection to Ti6Al4V alloys in seawater. • Cr( Mo )SiN coatings were successfully fabricated using the unbalance magnetron sputtering system. • The oxidization behaviors of Mo element decreased the friction coefficient. • The wear mechanism would be transformed to tribochemical wear with an increase in the Mo content. • The more Mo element doping enhanced tribological performance of CrMoSiN coating in seawater. • The corrosion rate and current density were slowed down due to the passive behaviors of Mo element on coating's surface.

Antagonistic effect of electrochemical corrosion on the mechanical wear of Monel 400 alloy in seawater

The tribocorrosion behavior as well as the corrosion-wear interaction of Monel 400 alloy in seawater were investigated under varied loads. An abnormal antagonistic effect of corrosion on wear was found, which was highly related to the peculiar corrosion products in the shape of nanospheres only generated under the tribocorrosion condition due to the selective corrosion of Ni-rich components. A boundary lubrication layer, consisting of the nanospheres squeezed and spread by friction stress, leaded to the reduction of friction coefficient. Moreover, the material loss rate was greatly alleviated because the friction-induced surface delamination and sub-surface crack propagation were prevented.

Microstructural, morphological characterization and corrosion behavior of sand cast AlSi10Cu(Fe) alloy in chloride solution

In order to examine the relationship between the microstructure and the corrosion behavior in chloride solution, the microstructure of AlSi10Cu (Fe) sand cast aluminum alloy has been investigated by using different techniques including scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis and electrochemical measurements. The microscopic analysis and X-ray diffraction analysis show several phases in addition to matrix phase, including pores and phases at nano- and microscales. The average rate of micropores and nanopores is 4% and 5%, respectively. The nanoparticle size varies between 20 and 150 nm. Plates and corals-like silicon eutectic, rich-Cu phase and Chinese script phase (Al15(Mn,Fe)3Si2) have been observed. Energy-dispersive spectroscopy analyses show the presence of a new phase (Cu61.22 Zn25.39Ni11.85 Al1.54), and the pitting corrosion has been demonstrated to be initiated at the nanopores. The electrochemical measurements exhibited the effect of several elements and porosities on the corrosion kinetics that is controlled by charge transfer and diffusion phenomenon. Wide passive windows, followed by the breakdown of passive film and excessive dissolution, have been observed in 0.3 and 3 wt% NaCl solutions. The electrochemical measurements show a high corrosion rate which does not recommend the use of this alloy in seawater.

Effect of Copper(II) Ions on Corrosion Resistance of Al-Zn Coated 5052 Aluminum Alloy in Seawater

Effect of Copper(II) Ions on Corrosion Resistance of Al-Zn Coated 5052 Aluminum Alloy in Seawater

Tribocorrosion characteristics of CrMoSiCN/Ag coatings on Ti6Al4V alloys in seawater

CrMoSiCN/Ag coatings were deposited on Ti6Al4V alloys at the trimethylsilane flow of 15 sccm using closed-field unbalanced magnetron sputtering, and their microstructures were observed and analyzed using SEM, XRD, XPS and TEM, respectively. The coatings’ mechanical properties were measured using nano-indenter. The tribocorrosion characteristics of Ti6Al4V and CrMoSiCN/Ag coatings were investigated in seawater using tribocorrosion tester. The results revealed that the nanocomposite coatings consisted of (Cr, Mo)N solid solution, Ag nanocrystal and amorphous SiCNx matrix. As the Ag target current increased to 1.0 A, a large amount of Ag nanoparticles were observed on the coating surface. The coating hardness initially increased to 21.0 ± 0.7 GPa at the Ag target current of 0.4 A and then declined. After the Ag element was added into coatings, their tribocorrosion characteristics were improved. The tribocorrosion characteristics of coatings were much better than those of Ti6Al4V. The tribocorrosion characteristics of CrMoSiCN/Ag coating at the Ag target current of 1.0 A were the best in seawater.

Novel multifunctional nanocomposites for superior barrier, hydrophobic and mechanical properties of Mg alloy in marine environment

The impact of surface functionalized titanium carbide (TiC) nanoparticles on the electrochemical and mechanical properties of epoxy nanocomposite was investigated. The functional TiC nanoparticles were synthesized using pyrrole (Py) and 2-amino-5-mercapto-1,3,4-thiadiazole (AMTD) and characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), and thermogravitric analysis (TGA) techniques. The resultant novel nanocomposite coating on Mg alloy in seawater was investigated by Tafel polarization, electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) studies. Electrochemical studies revealed excellent corrosion protection performance and a decreased corrosion current density for the EP-AMTD/TiC (Rc = 4861.25 kΩ.cm2 and icorr = 3.75 μA/cm2) and the EP-Py/TiC nanocomposite coated Mg alloy (Rc = 3182.71 kΩ.cm2 and icorr = 5.65 μA/cm2) in comparison with the plain epoxy coated Mg alloy (Rc = 244.67.25 kΩ.cm2 and icorr = 9.55 μA/cm2) after 60 days of immersion. The results indicated that the functional TiC nanoparticles dispersed uniformly and retarded the propagation of aggressive ions to the coating/alloy interface. SECM observations confirmed the observation of least current at the scratched area of the EP-AMTD/TiC (2.1 I/nA) and the EP-Py/TiC (4.8 I/nA) coated alloy compared to pure epoxy coating (14.9 I/nA) even after 60 d immersion in seawater. SEM observations showed that reactive TiC nanofillers are dispersed uniformly. The changes in surface morphology, phase structure and composition were analyzed using SEM/EDX and XRD techniques. It was found that the intercalation of functional TiC nanoparticles in the epoxy coatings exhibited a smooth microstructure surface producing superior corrosion protection and mechanical properties. The mechanism of corrosion protection has been proposed.

Research Progress in Corrosion Behavior of Nickel Aluminum Bronze Alloys in Seawater

Research Progress in Corrosion Behavior of Nickel Aluminum Bronze Alloys in Seawater

Corrosion of B10 Cu-Ni Alloy in Seawater Polluted by High Concentration of NH4+

Corrosion of B10 Cu-Ni Alloy in Seawater Polluted by High Concentration of NH4+

Corrosion Mechanism of 5083 Aluminum Alloy in Seawater Containing Phosphate

As a material with good corrosion resistance, 5083 aluminum alloy has a great application prospect in marine environment. In this work, the corrosion characteristics of 5083 aluminum alloy in seawater containing phosphate were investigated with Potentiodynamic Polarization, Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy Analysis (EDSA), X-ray Photoelectron Spectroscopy (XPS) and Laser Confocal Microscope. The results indicated that the effects of phosphate in seawater were two-fold. Firstly, phosphate slightly accelerated the corrosion of 5083 in seawater in the early stage of corrosion. HPO42− competed with OH− in the adsorption process on the alloy surface, which weakened the contact between OH− and Al3+ near the interface of the alloy, and inhibited the formation as well as the self-repair of the passive film, thus accelerating the activation dissolution process. Compared with the natural seawater, the charge transfer resistance of 5083 in the seawater containing phosphate decreased faster during the early stage of corrosion, and the corrosion current density icorr was higher in seawater containing phosphate. On the other hand, the addition of phosphate would not affect the cluster distribution of the second phase of 5083 in seawater, but it changed the composition of the corrosion product layer and had an obvious inhibitory effect on the local corrosion of 5083 in seawater. After 16-day exposure, shallower and more sparsely distributed pits could be observed on the derusted surface of 5083 in the seawater containing phosphate, and the pitting coefficient in the seawater containing phosphate was significantly lower than that in natural seawater. The reduction of pitting tendency could be realized mainly through two ways. First, the HPO42− adsorbed on the surface of the passive film in the early stage of corrosion and repeled the corrosive anions such as Cl−. Second, phosphate participated in the construction of the CaHPO4 precipitation film, which acted as a barrier and protection.

Electrochemical evaluation of inhibition efficiency of some nonionic surfactants based on tolyltriazole derivatives on the corrosion of Cu-Zn alloy in seawater

Two nonionic surfactants based on tolyltriazole derivatives namely: 5-methyl-1 Decaethoxide-benzotriazole, TTA (12) and 5-methyl-1 Tetracosaethoxide-benzotriazole, TTA (24) were synthesized and evaluated as corrosion inhibitors for 65Cu-35Zn alloy dissolution in aerated seawater. The corrosion inhibition capability of these nonionic surfactants has been investigated in seawater solution using potentiodynamic polarization, electrochemical impedance spectroscopy, EIS, and scanning electron microscopic SEM/EDX measurements. According to both potentiodynamic polarization and EIS measurements, it has been found that the investigated tolyltriazoles compounds, TTAs, work as efficient inhibitors for 65Cu-35Zn corrosion and the protection aptitude raised by increasing the concentration of inhibitors. EIS measurements indicated that the charge-transfer resistances increase upon increasing the TTAs concentration. It was found that the percentage inhibition efficiency (η%) increases by increasing the inhibitor concentration. Also, the results showed enhancement in inhibition efficiencies with decreasing the molecular size of the surfactant or the degree of ethoxylation at low concentration. At high concentration, the inhibition efficiency of the different inhibitors independent on the degree of ethoxylation. Potentiodynamic polarization curves indicated that the inhibitors under investigation act as mixed type. Finally, the surface characterization of the protective film formed on 65Cu-35Zn surface was examined by using SEM and energy dispersive X-ray, EDX, techniques. Adsorption of TTA, TTA(12), TTA(24) on the surface of Cu-35Zn in seawater, follows the Langmuir adsorption isotherm. The adsorption free energy of inhibitors on 65Cu-35Zn alloy reveals a strong physical adsorption of the inhibitor on the metal surface.

К ВОПРОСУ О ПОДТВЕРЖДЕНИИ ИДЕНТИЧНОСТИ МЕХАНИЗМА КОРРОЗИОННОГО РАЗРУШЕНИЯ АЛЮМИНИЕВЫХ СПЛАВОВ (обзор) Часть 2. Коррозия в морской воде

The paper presents an overview of studies of the corrosion destruction mechanisms of aluminum alloys in seawater. The main factors that have the greatest impact on corrosion are considered: physical and chemical parameters, the depth of the test objects, as well as the role of biofouling. It has been determined that the parameter of the species composition of the fouling organisms is an important factor in the corrosion of metals in seawater and should be taken into account when identifying the mechanism of corrosion destruction during tests under various conditions.

Investigation of Liquid Droplet Impingement Erosion Corrosion based on the Flow Rate of Anodized 5083-H321 Al Alloy in Seawater

Investigation of Liquid Droplet Impingement Erosion Corrosion based on the Flow Rate of Anodized 5083-H321 Al Alloy in Seawater

Stabilization of AZ31 Mg alloy in sea water via dual incorporation of MgO and WO3 during micro-arc oxidation

This study investigated the surface characteristics of WO3-MgO oxide layers formed on AZ31 Mg alloy via micro-arc oxidation (MAO). A series of MAO coatings was performed in an alkaline-aluminate electrolyte containing two different concentrations (2 and 4 g/L) of WO3 nanoparticles, and the results were compared to those without WO3 particles. Microstructural observations revealed that the addition of 2 g/L of WO3 nanoparticles into the electrolyte led to a uniform distribution of nanoparticles throughout the thickness of the oxide layer. In contrast, WO3 nanoparticles tended to agglomerate on the surface upon the inclusion of 4 g/L of WO3 into the electrolyte. The filling of structural defects due to the uniform incorporation of WO3 in the case of 2 g/L WO3 would be responsible for the superior corrosion resistance of the MAO-treated AZ31 Mg alloy substrate.

Effect of Cast Defects on the Corrosion Behavior and Mechanism of UNS C95810 Alloy in Artificial Seawater.

To study the effect of cast defects on the corrosion behavior and mechanism of the UNS C95810 alloy in seawater, an investigation was conducted by weight loss determination, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD) and electrochemical testing of the specimen with and without cast defects on the surface. The results show that the corrosion rate of the alloy with cast defects is higher than that of the alloy without cast defects, but the defects do not change the composition of the resulting corrosion products. The defects increase the complexity of the alloy microstructure and the tendency toward galvanic corrosion, which reduce the corrosion potential from −3.83 to −86.31 mV and increase the corrosion current density from 0.228 to 0.23 μA⋅cm−2.

Wear behavior of TC4 titanium alloy and 2205 stainless steel friction pair in different media

In order to choose the material of high-pressure pump in seawater desalination, the friction pair of TC4 titanium alloy and 2205 duplex stainless steel was studied in detail. Friction and wear tests were carried out under dry friction, pure water, and seawater media. The friction coefficient and wear extent of friction pair were obtained quantitatively, and the surface topography of friction samples was analyzed. The results showed that the abrasion of 2205 stainless steel and TC4 titanium alloy in seawater was less than in pure water and air/dry friction due to the lubrication effect of seawater medium. The abrasion resistance of 2205 stainless steel was better than that of TC4 titanium alloy. Compared with the rotating speed, the load has little effect on the friction coefficient.