Optimal Corrosion Resistance Research Articles

Effect of Alternating Current on Passive Film and Corrosion Behavior of Pipeline Steel with Different Microstructures in Carbonate/Bicarbonate Solution

The relationship between microstructure and alternating current (AC) corrosion behavior of X80 pipeline steel was systematically studied in CO32−/HCO3− solution using corrosion tests and surface analysis technology. The results show that AC prevents the formation of passive film and decreases its stability. AC generates a different damage effect to the passive film on steels with various microstructures. The passive film of normalized microstructure steel has a relatively high stability, followed by the hot-rolled steel, and that of the annealed sample is the most unstable. The influence of AC on passive film of steels with various microstructures causes a difference in the corrosion resistance. The corrosion form of steels with different microstructures applied with AC displays the obvious characteristic of localized corrosion. The normalized microstructure has the optimum corrosion resistance, followed by the hot-rolled steel, and the annealed steel possesses the worst corrosion resistance. The difference in the AC corrosion behavior of X80 steels may be related to the microstructure.

Synthesis of Ni–Fe and Ni–Fe/ZrO2 composite coating and evaluation of its structural and corrosion resistance

Ni–Fe/ZrO2 nanocomposite coating was fabricated by pulse electrodeposition in the presence of suspending ZrO2 nanoparticles. Ni–Fe alloy coating were also prepared for comparison. The effects of electrodeposition parameters, Fe2+ ions and ZrO2 concentration on the nanocomposite coating were examined with various methods. All coatings exhibit dense, compact and crack-free structures. The morphology slightly altered at different conditions. Fe content is more sensitive to the deposition parameters and greatly affects the chemical composition and phase structure of Ni–Fe matrix. Current density affects the composition rather than the texture of Ni–Fe matrix. The texture, composition and properties of Ni–Fe/ZrO2 composite coating were influenced by pulse frequency, duty cycle and ZrO2 concentration. The Ra of Ni–Fe/ZrO2 nanocomposites are about 6.2–37.1 nm, depending on the process parameters. The preferred orientation is (200) texture and the process parameters influenced the RTC value. The higher content of ZrO2 results in the rougher surface. 12.5 g L−1 FeSO4·7H2O and 4 A dm−2 was the suitable parameters for the optimal composition and corrosion resistance of Ni–Fe alloys. The optimal composition of Ni–Fe/ZrO2 deposits was 74.7 ± 0.4 at.% Ni, 16.8 ± 0.5 at.% Fe and 8.5 ± 0.2 at.% ZrO2.

Effects of the CNT Content and Plating Solution pH After Purification on the Performance of Ni–P/CNT Composite Coating

After CNTs were purified, Ni–P/CNT composite coating was prepared at different CNT contents and plating solution pH values by univariate experimental method. Besides, the surface appearance, hardness, corrosion resistance and wear resisting property of the coating were tested and analyzed by X-ray diffractometer, scanning electronic microscope, microhardness tester, electrochemical workstation, tribometer and other means. The results suggest that fibers on the surface of purified CNTs are clear and well dispersed. During dummy plating, purified CNTs were more likely to deposit on Ni–P coating. A proper amount of CNTs could reasonably improve the structure of Ni–P/CNT composite coating; different pH values would lead to different specific gravities of alloying elements and CNT deposition, and a reasonable pH value would help the coating reach the optimal hardness, wearability and corrosion resistance. In general, Ni–P/CNT composite coating has the best comprehensive performance when the CNT content is 40 mg/L and pH value is 6.

Corrosion resistance of dodecanethiol-modified magnesium hydroxide coating on AZ31 magnesium alloy

A hydrophobic surface coating on AZ31 magnesium alloy was fabricated by combining hydrothermal treatment and subsequent chemical modification with 1-dodecanethiol (DT). The structure and morphology of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The roughness of samples was examined by atomic force microscope (AFM). The corrosion resistance of the hydrophobic coatings was investigated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results revealed that the hydrophobic coatings effectively improved the corrosion resistance of the AZ31 alloy. The hydrophobic surface obtained in presence of 10 mmol L−1 DT showed a maximum static water contact angle of 105.5° and optimum corrosion resistance. There exists a “threshold” DT concentration for achieving hydrophobic coating on AZ31. Addition of an excess of DT decreased the water contact angle and corrosion resistance of coating. In the discussion part of this paper, a comparison was made with previous works. Finally, a corrosion mechanism of the coating was proposed and discussed.

Corrosion resistance of a silane/ceria modified Mg-Al-layered double hydroxide on AA5005 aluminum alloy

The present work aimed at assessing the electrochemical behavior and the corrosion inhibition performance of Mg-Al-layered double hydroxide (LDH) coatings modified with methyltrimethoxysilane (MTMS) and cerium nitrate on AA5005 aluminum alloy. The chemical compositions and surface morphologies of the coatings were investigated by XRD, FT-IR and FE-SEM, while their corrosion resistance was evaluated by electrochemical and immersion tests. An optimum corrosion resistance of the composite coatings was obtained by adding 10−2 mol·L−1 cerium nitrate. An excess addition of cerium nitrate resulted in a loose structure and poor corrosion resistance of the coating. The corrosion mechanism of the composite coatings was proposed and discussed.

Study on Corrosion Resistance and Bio-Tribological Behavior of Porous Structure Based on the SLM Manufactured Medical Ti6Al4V

Titanium and its alloy, especially Ti6Al4V is one of the most widely used metal due to its excellent properties. Selective laser melting, which is known as additive manufacturing is considered as a suitable method to manufacture Ti6Al4V parts. To print a more analogous Ti6Al4V artificial bone, laser power was changed by taking volume porosity, corrosion resistance and wear resistance into consideration. The testing results showed that sample printed using 200 W showed a relative optimal corrosion resistance and volume porosity in all these five samples (the value of corrosion voltage is − 0.352 V), while it showed the best bio-tribological behavior, and its wear volume is as low as 5.90 μm3. Summarize the 5 sets of experimental samples, the Ti6Al4V part printed using 180–200 W were the most prominent in the test, its overall performance was, indeed, best fit to print artificial Ti6Al4V bone, because it is similar to bone, there are a large number of microporous structures. Corrosion mechanism At the oxide film/metal interface, the metal undergoes an ionization reaction to form M2+, the O2 molecule forms an atomic state of oxygen by physical adsorption on the metal surface, and then chemically adsorbs to form O−, and is bonded to the oxide crystal lattice in an O2− state to form a new oxide which hinders further oxidation. The presence of voids also reduces the corrosion resistance of the substrate material due to the increased corrosion area, and corrosive ions are more likely to penetrate into corrosive materials. Wear mechanism Ploughing wear and oxidation erode can be seen on the surface while ploughing wear was the most significant mechanism. From the EDS results, it can be found that the abrasive dust was mainly composed of TiO2. This phenomenon was due to the fact that Ti is a kind of active metal and it is easily oxidized. That is the reason why oxidation erode can also be found on the surface and it further explained the equivalent circuit given in corrosion behavior section.

Facile synthesis and electrochemical properties of a novel Ni-B/TiC composite coating via ultrasonic-assisted electrodeposition.

A novel Ni-B/TiC composite coating was synthesized by ultrasonic-assisted direct current electrodeposition. Ultrasonic technology was adopted to prevent the agglomeration of nanoparticle, improve the structure and corrosion resistance, using an ultrasonic bath at frequency 40 KHz and acoustic power 300 W. The influences of current density and deposition time on its structure and electrochemical behaviors were studied. Under ultrasonic dispersion, the composite coatings are smooth, compact with protrusion structure sparsely distributed on it. The average roughness (Sa) was about 13.6-26.1 nm. The crystallite size is 10-21 nm. The preferred orientation is Ni (1 1 1) texture. EIS results indicated that the corrosion resistance was greatly improved by ultrasonic-assisted method. The corrosion mechanism is consistent with one-time constant EEC model of Rs(CPEdlRct). With the increase of immersion time, the Rct of the composite coating often first increased and then decreased. Under ultrasonic, current density 2 A dm-2 and deposition time 20 min were the appropriate parameters for the optimal corrosion resistance and excellent long-term electrochemical stability in 3.5 wt% NaCl corrosive solution. This coating shows good application prospect for corrosion protection in aggressive environment.

Influence of Preaging Treatment on Bake-Hardening Response and Electrochemical Corrosion Behavior of High Strength Al-Zn-Mg-Cu-Zr Alloy

The influence of preaging (PA) treatments on the bake hardening (BH) response of a AlZnMgCuZr aluminum alloy which served as automotive body structures were studied in this paper. A novel two-step PA treatment was particularly designed and further employed. The mechanical properties of the alloy were tested in detail. The microstructure was characterized by optical microscope (OM), transmission electron microscopy (TEM) and 3D measuring laser microscope (3D–MLM). Meanwhile, the corrosion behavior was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results indicated that the PA treatment was beneficial for the improvement of BH response after baking at 180 °C immediately after the solution treatment and the micro-hardness reached the peak value (194 HV) after 10 h holding, which had a percentage improvement of 110.87% compared to the hardness under the solution condition. The PA treatments decreased natural aging (NA) adverse effects, while it had the lowest NA effect and optimal BH response under 120 °C/20 min. Such a novel two-step PA treatment was revealed further to decrease the NA effect and increase the BH response compared to the optimal PA treatment, in particular, the BH value could reach 168 MPa and was 21.7% higher than that of optimal PA + NA treatment. The optimal corrosion resistance has been shown up by the combined characterizations of potentiodynamic polarization curves, EIS Nyquist plots, and 3D–MLM images.

Effect of Temperature on Corrosion behavior of Copper Silver Phosphorus Brazing Alloys in Chloride Containing Solution

The groups of phosphorus-containing brazing alloys are the most favored filler metals used for joining copper and copper-base alloys. These brazing alloys are expected to have the optimum corrosion resistance during the application. However, failures arise at the braze joint generally caused and initiated by the corrosion of the brazing alloys when used at higher temperature than the room temperature. Since most studies of the phosphorus containing brazing alloys were performed at room temperature, this work has been extended to investigate the effect of various temperature on the corrosion behavior. Electrochemical measurements were carried out to observed the temperature effect with the temperature variation of 25, 40, 55 and 70 °C in 3.5% NaCl electrolyte. As the results, the copper-silver-phosphorus brazing alloy was undergone a selective dissolution by the attack of Cl-to the copper element. The temperature dependence of the alloy showed in agreement with the relationship of 2.3RT/F that have similar manner on pure copper tafel region. The schematic diagrams of the corrosion process were then proposed. This work could be helpful to understand in the field practically because the application temperature is usually higher than that of room temperature in general.

Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings

The air-plasma-sprayed ceria and yttria-stabilized zirconia (CYSZ) coating was modified by selective laser remelting and Al deposition to enhance hot corrosion resistance. The dotted coating was obtained after selective laser remelting. Magnetron sputtering was used to deposit an Al film on the dotted coating, and a vacuum heat treatment was subsequently performed to produce a dense α-Al2O3 overlay. Hot corrosion behavior of the following three types of coatings was investigated: plasma-sprayed, dotted, and dotted coatings combined with Al deposition (DA). Hot corrosion behaviors were evaluated in a mixture of 55 wt % V2O5 and 45 wt % Na2SO4 molten salts at 1000 °C for 30 h. The hot corrosion reaction between molten salts and zirconia stabilizers (Y2O3 and CeO2) led to the generation of monoclinic zirconia, YVO4, and CeVO4 plate-shaped crystals, and the mineralization of CeO2. The results indicated that the hot corrosion resistance of the DA coating was the best, and the dotted coating had superior hot corrosion resistance in comparison with the plasma-sprayed coating. The minimal surface roughness and dense dotted units improved the hot corrosion resistance of the dotted coating. The dense α-Al2O3 overlay with chemical inertness effectively inhibited the infiltration of molten salts, which led to the optimal hot corrosion resistance of the DA coating.

Corrosion resistance of Mg(OH)2/Mg–Al-layered double hydroxide coatings on magnesium alloy AZ31: influence of hydrolysis degree of silane

Mg(OH)2/Mg–Al-layered double hydroxide (LDH) coatings were modified with methyltrimethoxysilane (MTMS) on magnesium alloys. Effect of hydrolysis degree of silane solution on coating formation was investigated. Chemical compositions and surface morphologies of the coatings were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electronic microscopy (FESEM). Results indicated that the composite coatings consisted of polymethyltrimethoxysilane (PMTMS), LDH and Mg(OH)2. Electrochemical and hydrogen evolution measurements revealed that the composite coatings possessed good corrosion resistance, especially the ones prepared in a high hydrolysis degree of silane. The optimum corrosion resistance of the composite coating was LDH/PMTMS-3 coating, which had the lowest value of corrosion current density (5.537 × 10−9 A·cm−2) and a dense surface. Plausible mechanism for coating formation and corrosion process of MTMS-modified Mg(OH)2/Mg–Al-LDH coatings were discussed.

Enhanced corrosion resistance of waterborne polyurethane containing sulfonated graphene/zinc phosphate composites

Compared with solvent-based resins, waterborne resins still have defects such as insufficient anti-corrosion efficiency. In this paper, the sulfonated graphene/zinc phosphate composites were prepared as an anti-corrosion filler and doped into waterborne polyurethane resin. The morphology of composites is different from pure zinc phosphate. The optimal corrosion resistance can be obtained by adding 0.5 wt% sulfonated graphene/zinc phosphate fillers characterized by Potentiodynamic polarization curves and EIS analysis The corrosion current density (icorr) was 0.4252 μA/cm2 and the charged transfer resistance (Rct) was up to 10.937 × 103 Ω cm2, which show a good potential as anti-corrosive fillers in waterborne coatings system.

Electrodeposition of Ni W/ZrO2 nanocrystalline film reinforced by CeO2 nanoparticles: Structure, surface properties and corrosion resistance

Abstract To enhance the performance of nickel-tungsten (Ni W) matrix, Ni W/ZrO2 CeO2 nanocrystalline films have been fabricated by electrodeposition in the presence of zirconia (ZrO2) and ceria (CeO2) nanoparticles. The influences of process parameters on microstructural, surface properties and corrosion resistance of the nanocrystalline films were examined. Studies indicated that the fabricated films are dense, homogeneous and without cracks, comprising 23.7–28.7 wt% W, 3.9–4.9 wt% ZrO2 and 0.45–0.68 wt% CeO2. The film prepared at average current density (Iav) of 6 A dm−2, duty cycle (r) of 70% contains the highest content of ZrO2, CeO2 nanoparticles with the finer structure. The average roughness (Ra) is 79.1 nm for film formed at 2 A dm−2. The growth rate of the film is about 0.48–0.53 μm/min at Iav = 4 A dm−2 and r = 50%. The hardness first increases and then decreases with the maximum value at r = 70%, Iav = 6 A dm−2 and deposition time (t) of 40 min, respectively. Energy disperse spectroscopy (EDS) mapping, transmission electron microscope (TEM) and cross-sectional images illustrated that the ZrO2 and CeO2 particles had been homogeneously incorporated in the film. The electrochemical measurements illustrate that the optimal corrosion resistance of Ni W/ZrO2 CeO2 film could be obtained at r = 70%, Iav = 6 A dm−2 and t = 40 min. The incorporation of ZrO2 CeO2 in Ni W film would enhance the anti-corrosion properties and hardness. Ni W/ZrO2 CeO2 film owns superior hardness and excellent anti-corrosion properties, showing a broad application prospect in harsh environment.

Mechanical, magnetic properties and corrosion resistance of hybrid bonded magnet NdFeB - BaFe12O19

The hybrid bonded magnet NdFeB - BaFe12O19 has been made. The composition of BaFe12O19 was varied as 0, 3, 5, 8, and 10 wt%. The preparation process was started by mixing BaFe12O19 powder with NdFeB (MQP-B+), then mixed with exopy resin binder of 8 wt% and subsequently compacted with a pressure of 60 MPa to form a pellet. The pellet samples were heated in 10 mmbar of vacuum dryer at 90°C for 1 hour. Some parameters were measured such as mechanical properties (compressive strength), magnetic properties (magnetic flux density and hysteresis curve) and corrosion resistance. The results show that the hybrid bonded magnet NdFeB with 10 wt% BaFe12O19 exhibits the highest compressive strength of about 268,15 kgf/cm2. While the optimum corrosion resistance of bonded magnet NdFeB - BaFe12O19 is obtained by 5 wt% BaFe12O19 addition. It has a flux magnetic density of 1340 Gauss, remanence Br of 3,827 kG and coercivity Hcj of 8,924 kOe. According to the corrosion test result, it is found that the sample with higher content of Ba-ferrite has a better corrosion resistance compare to the sample with small content of Ba-ferrite.

Preparation and application of ZrC-coated flake graphite for Al2O3-C refractories

In the study, ZrC-coated flake graphite was prepared by molten salt synthesis and added to the Al2O3-C refractory. The effects of the molar ratio of Zr/C and the graphite particle size on ZrC-coated flake graphite were investigated. Moreover, the oxidation resistance of the prepared ZrC-coated flake graphite was evaluated. Finally, the effect of ZrC-coated flake graphite on the properties of the Al2O3-C refractory was investigated. The results indicated that Zr and C reacted completely as the Zr/C molar ratio decreased. Furthermore, with a decrease in the graphite particle size, the reaction between Zr and C was more complete and the size of the peeling layer decreased. When compared with natural flake graphite, ZrC-coated flake graphite exhibited better oxidation resistance. The Al2O3-C refractory with 3 wt% ZrC-coated flake graphite exhibited optimal oxidation resistance and that with 1 wt% ZrC-coated flake graphite exhibited optimal slag corrosion resistance ability.

Electrodeposition of Ni-W/TiN-Y2O3 nanocrystalline coating and investigation of its surface properties and corrosion resistance

The incorporation of TiN and Y2O3 nanoparticles together into Ni-W matrix have been investigated by pulse electrodeposition in present study. The microstructural, surface properties and corrosion resistance of Ni-W/TiN-Y2O3 nanocrystalline coating have been studied. It illustrated that the electrodeposited coatings have dense and nodular structure without defects. Results confirmed that TiN and Y2O3 particles were uniformly embedded in the composites. The embedded particles could improve the hardness and anti-corrosion properties of the obtained coating. The crystallite size calculated based on the preferred orientation (111) plane was of 14–17 nm, illustrating the formation of nanocrystalline structure. The mean Ra value was about 84.6 nm. Electrochemical impedance tests revealed that the preferred combination of operating parameters for optimum corrosion resistance was 70%, 1000 Hz, 40 min and 4 A dm−2. However, the best hardness and anti-wear properties were obtained at parameters of 50%, 500 Hz, 6 Adm−2 and 60 min. The extreme values of hardness and corrosion resistance were not realized simultaneously. The operating parameters should be kept in a certain balance to avoid the formation of inferior properties in any aspects of the coating; then the other performance advantages could be brought into full play. The preferred combination of operating parameters was optimized to be duty cycle of 70%, frequency of 1000 Hz, duration time of 40 min and average current density of 4 Adm−2, which enabled the electrodeposited coating optimum corrosion resistance and high mechanical properties.

Corrosion Behavior of Pipeline Steel with Different Microstructures Under AC Interference in Acid Soil Simulation Solution

Corrosion behavior of X65 pipeline steels with different microstructures under alternating current (AC) interference was investigated in acid soil simulation solution by potentiodynamic polarization curve, potentiostatic polarization curve and immersion test. The results show that superimposed AC causes a sharp increase in corrosion current density of X65 steel. With the increase in iAC, the corrosion current densities of steels with various microstructures increase, especially at high iAC. Hot-rolled steel mainly experiences uniform corrosion, with very slight pit corrosion. Serious corrosion degrees with intensive corrosion pits can be observed on the surfaces of normalized and quenched microstructure steels. The annealed steel exhibits the feature of non-uniform corrosion with some pitting. The steels with various microstructures applied with AC have different corrosion resistance. The normalized steel shows the worst corrosion resistance, then the quenched microstructure, and the hot-rolled steel displays the optimum corrosion resistance. The difference in the microstructure can result in difference in corrosion degree and occurrence position of pitting corrosion of X65 steel. The normalized microstructure composed of polygonal ferrite and a large amount of pearlite and bainite is the most susceptible to AC corrosion.

Effect of concentration of Ce(NO3)3 · 6H2O and temperature on the corrosion resistance of Al2O3/cerium oxide composite films on 1060 Al alloy

In this paper, Al2O3/cerium oxide composite films were prepared on the surface of aluminum by anodic oxidation and chemical solution deposition. The aluminum was firstly anodized in sulfuric acid, then treated with different concentrations of Ce(NO3)3 · 6H2O solution at different temperatures. X‐ray diffraction (XRD), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and electrochemical polarization tests were used to characterize the properties of the composite films. The results indicate that the Al2O3/cerium oxide composite films successfully form on 1060 Al alloy, and the best condition of film‐forming is 2 g/L Ce(NO3)3 · 6H2O and 50 °C. Al2O3/cerium oxide composite film under this condition has a uniform, smooth, and pyknotic surface topography and optimal corrosion resistance. The corrosion density at that time is 1.106 × 10−6 A/cm2 and the corrosion potential is −0.458 V.

Soft magnetic properties and corrosion resistance of Fe-Co-B-M (M[dbnd]Nb, Ta and NbNi) metallic glasses

Fe-based metallic glasses (MGs) with good soft magnetic properties, high thermal stability combined with high corrosion resistance should have greatest potential for wide variety of applications. In this work, the effects of Nb, Ta and NbNi additions on the glass forming ability (GFA), thermal stability, magnetic properties and corrosion resistance of the as-spun Fe-Co-B-based amorphous ribbons have been investigated. The (Fe0.7Co0.3)75B21Nb4 and (Fe0.7Co0.3)75B21Ta4 MG possess the larger supercooled liquid region >40 K, presenting a high GFA. Via appropriate adjustment of the Fe/Co content ratio (4:1), the glass transition temperature and onset crystallization temperature of the (Fe0.8Co0.2)75B21Nb4 MG reach up to 800 and 826 K, respectively, indicating the best thermal stability. All the amorphous ribbons show the soft magnetic properties identified by the coercivity <1.3 Oe. Moreover, the (Fe0.8Co0.2)75B21Nb4 MG exhibits the good soft magnetic properties with a high saturation magnetization (Ms) up to 206 emu/g (1.92 T). Besides a positive role of Nb addition, the enhanced Ms can be attributed to the increased magnetic moment with substitution of Co by Fe, and the easy movement of magnetic domains induced by the decreased atomic packing density. In addition, the tested samples are all spontaneously passivated with a large passive region during electrochemical polarization measurement in the seawater solution. Especially, the (Fe0.7Co0.15Ni0.15)75B21Nb4 MG presents the optimal corrosion resistance with the most positive corrosion potential.

Effect of Ca Content on Properties of Extruded Mg-3Zn-0.5Sr-xCa Alloys for Medical Applications

Mg-3Zn-0.5Sr-xCa(wt.%) (x=0, 0.2, 0.5) alloys were fabricated by casting and hot extrusion. X-ray diffraction (XRD) and optical microscopy observation showed that the microstructure of Mg-3Zn-0.5Sr-xCa alloys was composed of α-Mg matrix and Mg17Sr2 phase precipitated along grain boundaries. The tensile strength of the alloy increased from 255MPa to 305MPa with increasing Ca content from 0 to 0.5wt%, but the elongation to fracture of the alloys was 19.45%, 28.7% and 15.2% respectively, indicating that coarse precipitation increased the risk of crack initiation and propagation along the grain boundaries leading to reduced ductility of Mg alloys. The polarization curves revealed that Mg-3Zn-0.5Sr-0.2Ca has the highest corrosion potential and the lowest corrosion current density indicating the optimum corrosion resistance. In cytotoxicity test, Mg-3Zn-0.5Sr-xCa alloys were harmless to mouse osteoblastic and Mg-3Zn-0.5Sr-0.2Ca alloy exhibited optimal biocompatibility.