Neutral Salt Spray Corrosion Research Articles

Hot-dip galvanizing process and coating corrosion behavior of fe-mn-al-c steel

The temperature of the zinc bath and the immersion duration are critical factors that significantly impact the surface quality and adhesion of batch hot-dip galvanizing coatings. This study focuses on the influence of different zinc bath temperatures (460, 490, and 520 °C) and immersion duration (1, 3, 5, and 10 min) on the hot-dip galvanized coatings of Fe-Mn-Al-C lightweight steel, which were characterized using scanning electron microscopy and energy dispersive X-ray analysis. The results demonstrate that with the increasing zinc bath temperature and immersion duration, the coating thickness and bond strength initially increase and then decrease. The inhibition layer in the coating gradually fractures and thickens with the rising temperature, leading to changes in the alloy phases within the coating. The optimal batch hot-dip galvanizing condition for the experimental steel is immersing at 490 °C for 3 min. Furthermore, we conducted a neutral salt spray corrosion test on the specimens under the optimal batch hot-dip galvanizing condition to study their corrosion behavior and mechanism and evaluate the impact of batch hot-dip galvanizing on the corrosion resistance of Fe-Mn-Al-C steel.

Corrosion Behavior of 30 ppi TAD3D/5A05Al Composite in Neutral Salt Spray Corrosion

This study created ceramic preforms with a 3D network structure (TAD3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD3D. The corrosion behavior and resistance of TAD3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl2O4, Al(OH)3, and Al2O3. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion.

Excellent corrosion resistance and good wear resistance of amorphous AlTiO coating prepared by arc ion plating

An amorphous AlTiO coating was prepared using arc ion plating. Its wear resistance and corrosion resistance were compared with those of AlTiN coating. The results indicated that the amorphous AlTiO coating had a dense structure, with H/E ratio and friction coefficient of 0.06 and 0.70, respectively, which were approaching to the values for the AlTiN coating. The friction and wear tests demonstrated that both AlTiN coating and AlTiO coating had good wear resistance. Electrochemical experiments demonstrated that the AlTiO coating exhibited excellent corrosion resistance, with a corrosion current density (Icorr) only 1.97% of that of the AlTiN coating. After neutral salt spray corrosion test with a duration of 500 h, the AlTiN coating was completely corroded, while only two corrosion spots were observed on the AlTiO coating.

A method for preparing alloy coating on the aluminum alloy substrate via laser cladding technology to prevent the galvanic corrosion of TC4/5083 couple

The Cu-Ni-Cr alloy coating was prepared on 5083 aluminum alloy substrate using laser cladding technology. The microstructure of the coating and its galvanic corrosion resistance in contact with TC4 alloy were studied. The results indicate that the Cu-Ni-Cr alloy coating primarily consists of Al-rich dendrite phase and Cu-rich matrix phase. The shear strength of the Cu-Ni-Cr alloy coating is 154.68 MPa, which is greater than that of the aluminum alloy substrate. The galvanic current density of the TC4/Cu-Ni-Cr couple is 0.05 μA·cm−2. The neutral salt spray corrosion test results demonstrate that the Cu-Ni-Cr alloy coating exhibits excellent resistance to galvanic corrosion. The coating can attenuate the galvanic corrosion effect when it is in contact with the TC4 titanium alloy, offering new solutions to address the galvanic corrosion challenges between titanium alloy and aluminum alloy in marine environments.

Properties of Padding Welds Made of CuAl2 Multiwire and CuAl7 Wire in TIG Process.

This paper presents the influence of the Hot Isostatic Pressing (HIP) process on the structure, mechanical properties and corrosion resistance of padding welds made using the TIG method from aluminium bronzes-CuAl7 and CuAl2 (a composite bundled wire). The tested CuAl7 material was a commercial welding wire, while the CuAl2 composite was an experimental one (a prototype of the material produced in multiwire technology). The wire contains a bundle of component materials-in this case, copper in the form of a tube and aluminium in the form of rods. The padding welds were manufactured for both the CuAl7 wire and the CuAl2 multiwire. The prepared samples were subjected to the Hot Isostatic Pressing (HIP) process, chemical composition tests were performed, and then the samples were subjected to observations using light microscopy, Vickers hardness testing, electrical conductivity tests, and apparent density determination using Archimedes' Principle. Tribological tests (the 'pin on disc' method) and neutral salt spray corrosion tests were conducted. The padding weld made of CuAl2 multifiber material subjected to the HIP process is characterized by an improvement in density of 0.01 g/cm3; a homogenization of the hardness results across the sample was also observed. The average hardness of the sample after the HIP process decreased by about 15HV, however, the standard deviation also decreased by about 8HV. The electrical conductivity of the CuAl2 welded sample increased from 16.35 MS/m to 17.49 MS/m for the CuAl2 sample after the HIP process. As a result of this process, a visible increase in electrical conductivity was observed in the case of the wall made of the CuAl2 multiwire-an increase of 1.14 MS/m.

An experimental study on the corrosion behaviors and mechanical properties of Q345qD steel in neutral salt spray environment considering stress state

This paper investigates the corrosion behavior and mechanical property degradation of Q345qD steel in the marine atmosphere through force-holding neutral salt spray corrosion experiments. A digital microscope is utilized to obtain the surface morphology of corroded specimens. Mass losses and equivalent corrosion depths for different corrosion times and stress levels are quantitatively determined. Statistical laws of pitting corrosion are formulated based on digital microscope observations. Typical mechanical properties of corroded steel are also obtained through tensile tests. Results show that stress accelerates the pitting process but has little impact on the mass losses of general corrosion. The relationship between equivalent corrosion depth and corrosion time can be well described by a linear function. Corrosion can decrease the apparent strengths of Q345qD steel and trigger a transition from ductile fracture to brittle fracture. To ensure the safety and durability of engineering structures, a maximum mass loss ratio of 10% is suggested.

Study on magnetic pulse crimping process for joining large-diameter aluminum alloy tube/magnesium alloy shaft

A structure for joining 6061T6 aluminum alloy tube and AZ31B magnesium alloy shaft via the magnetic pulse crimping process was proposed. The forming process, mechanical properties, failure modes, and corrosion behaviors of the joint were studied. The results showed that the enormous Lorentz force drove the wall of aluminum alloy tube to move towards the groove of magnesium alloy shaft at high velocity, thus realized mechanical locking and formed joint. Through torsion tests, it was found that the mechanical properties of the joint with different process parameters varied. There were two failure modes for joint: torsional separation and torsional crack. Specifically, discharge time, groove angle, and discharge energy for torsional crack were, respectively, 1, 90°, and 28 kJ and 3, 90°, and 25 kJ. The maximum torque was up to 961.99 N·m under discharged twice, 90° groove angle, and 25-kJ discharge energy. Through neutral salt spray corrosion tests, it was found that the maximum torque only decreased by 28.03% after corrosion for 192 h. It indicated that the corrosion resistance of joint was good relatively.

An empirical model based on peeling strength for estimating corrosion failure of Cu/Al clad plates in the atmospheric environment

In this paper, an empirical model based on peeling strength (PS) for estimating corrosion failure of Cu/Al clad plates was established through indoor-accelerated neutral salt spray corrosion experiments. SVET results show that Al performed a negative potential difference while Cu performed positive. The corrosion rate of Al was considered as that of the Cu/Al clad plate due to corrosion only occurred on Al. The largest current density occurred on Al at the interface of Cu/Al clad plates, corresponding to the largest corrosion rate. The bonded area between Cu and Al decreased as the corrosion time increased, thus PS reduced. The failure model was related to the concentration of Cl-, corrosion time and PS, which was validated accuracy through experiments. According to GB/T 32468–2015 for Cu/Al clad plates, clad plates were identified failure when PS＜12 N/mm.

Temperature Effect on the Corrosion Behavior of Copper inhibited by3,4'-bi-1,2,4-Triazole in neutral salt-spray (NaCl 3%) Medium


 Abstract
 The temperature effect on the corrosion behavior of copper that was inhibited by 3,4'-bi-1,2,4-Triazole in NaCl 3% Medium was investigated using potentiodynamic polarization techniques. Inhibition effect was found to increase with decreasing the temperature. Polarization curves showed that 3,4'-bi-1,2,4-Triazole (bTA) act as mixed type inhibitors in 3% NaCl Medium. The obtained results showed that the 3,4'-bi-1,2,4-Triazole could serve as an effective inhibitor of the copper corrosion in 3% NaCl Medium at various temperature up to 55°C. 
 Keywords: copper, neutral salt-spray corrosion; electrochemical corrosion; corrosion behavior; corrosion resistance, 1,2,4-Triazole.

Effects of nitriding on salt spray corrosion resistance of additively manufactured 17-4 PH steels

• Study on effects of nitriding temperatures on NSS corrosion on AM 17-4 PH steel material. • Larger red rust formation was observed on as-built when compared with nitrided samples. • Higher volume of reduced grain size with precipitates was observed in the microstructure of nitrided samples. • Passive protective film with chromium and iron nitrides exhibited the best corrosion resistance at 580 o C. This work addresses the effects of varying nitriding temperatures of 530, 560 and 580 °C for 2 hours on corrosion resistance of additively manufactured (AM) 17-4 PH steels, using neutral salt spray (NSS) method for 104 hours. The morphological analysis indicated the presence of columnar grains along the built direction of additive manufacturing process. The refined grain size and the amount of the precipitates increased with an increasing nitriding temperature. The results of the analysis showed that a minimum weight loss was observed at 580 o C, due to the formation of passive oxide layer and nitrogen rich precipitates on the surface. The X-ray diffraction (XRD) showed the presence of these compounds: Cr 2 N, (Fe, Cr) 4 N, (Fe, Cr) 2-3 N, Fe 2 O 3 , FeOOH, and Cr 2 O 3 on the nitrided sample after the salt spray test.

Preparation and Properties of Three-dimensional Graphene-based Multifunctional Thermal Control Coating

According to the requirements of spacecraft light alloy materials for thermal control, anti-static and corrosion protection, based on the synthesized three-dimensional graphene functional filler, a multifunctional thermal control coating with high emissivity, anti-static and anti-corrosion properties was prepared on magnesium alloy materials. By testing the coating properties, the hemispherical emissivity was 0.91,volume resistivity was 104Ωm and neutral salt spray corrosion resistance was more than 800 hours.

Preparation and Properties of Three-dimensional Graphene-based Multifunctional Thermal Control Coating

According to the requirements of spacecraft light alloy materials for thermal control, anti-static and corrosion protection, based on the synthesized three-dimensional graphene functional filler, a multifunctional thermal control coating with high emissivity, anti-static and anti-corrosion properties was prepared on magnesium alloy materials. By testing the coating properties, the hemispherical emissivity was 0.91,volume resistivity was 104Ωm and neutral salt spray corrosion resistance was more than 800 hours.

Effect of rare earth on inclusion evolution and corrosion resistance of HRB400E steel

AbstractThe effect of rare earth elements Ce and La on the evolution behavior of inclusions in HRB400E steel was studied through experimental observations and thermodynamic calculations. Neutral salt spray corrosion experiments were also conducted to investigate the effect of Ce–La on the corrosion resistance of steel. The results showed that the typical inclusions in steel without rare earth were MnS and MnO–SiO2. A small amount of Mn–Si–O–S inclusions was also observed. After adding rare earth, the typical inclusions were transformed into isolated (Ce,La)2O2S, (Ce,La)2O3 + MnS, and (Ce,La)2O2S + MnS complex inclusions. The thermodynamic calculations indicated that the rare earth elements in molten steel preferentially reacted with MnO–SiO2 inclusions and dissolved oxygen and sulfur to form (Ce,La)2O3 and (Ce,La)2O2S. Small amounts of [S] and [Mn] adhered to the surface of the nucleated rare earth inclusions to form complex inclusions. After Ce–La treatment, the corrosion rate of the steel decreased from 3.491 to 1.992 mm year−1, and the corrosion resistance was improved. The change in corrosion behavior is due to the modification of the inclusions into rare earth inclusions with good compatibility with the steel matrix.

Influence of the drawing process on corrosion behaviour of hot-dip galvanised wires

The phenomenon of corrosion on wires and springs covered with an anti-corrosive zinc coating was investigated. To assess the corrosion resistance of galvanised wires, tests were carried out in the standard neutral salt spray corrosion test and in the sulphur dioxide test with general moisture condensation. The spring corrosion process depends on the wire drawing technology. The research showed that the higher the drawing speed and angle, the more dynamic the corrosion development.

Comparative Study on the Corrosion Resistance of 6061Al and SiC3D/6061Al Composite in a Chloride Environment.

Interface problems and the destruction of the continuity of the oxide film in the Al matrix usually reduce the corrosion resistance of the material. In this paper, the corrosion resistance of Al matrix composites (AMCs) was improved by introducing the silicon carbide skeletons (SiC3D) obtained with polymer replica technology. SiC3D/6061Al was fabricated by infiltrating molten 6061Al alloy in the oxidized SiC3D using the low-pressure casting method. The corrosion resistance performances of 6061Al and SiC3D/6061Al in NaCl solution were studied by electrochemical, neutral salt spray corrosion (NSS), and salt leaching (SL) tests. Results show corrosion resistance of SiC3D/6061Al is higher than that of 6061Al alloys by open circuit potential (OCP), potentio-dynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. However, NSS and SL tests show the corrosion resistance of SiC3D/6061Al is lower than that of 6061Al alloy. The reason is a corrosion resistant and anti-oxidation network macrostructure with large interface recombination, few concentrated interfaces, and a small specific area that formed in SiC3D/6061Al. SiC3D cannot damage the continuity of the Al2O3 passivating film, and the network macrostructure greatly improves the corrosion resistance performance.

Corrosion Resistance and Formation Mechanism of Anodic Oxidation–Organic Structure Super‐Hydrophobic Self‐Assembled Film

AbstractIn this article, the perfluorooctyltriethoxysilane (POTS) is used as a low surface energy substance to self‐assemble in Al2O3 surface to prepare a corrosion‐resistant composite film by anodization and self‐assembly technology. The morphology, structure, wettability, and chemical composition of the composite film are characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, water contact angle, and X‐ray photoelectron spectroscopy. The corrosion resistance of the composite film is tested through electrochemical test and the neutral salt spray test, and various pollution simulations are performed to test the self‐cleaning performance of the film. The formation mechanism of the film is discussed by quantum chemical calculations. The results show that compared with Al alloy, the AC impedance of the composite film is increased by five orders of magnitude, the corrosion current density is reduced by three orders of magnitude, and the neutral salt spray corrosion test reaches 31 days. Meanwhile, theoretical studies of quantum chemical calculations show that Al2O3/POTS film is adsorbed on the surface of Al alloys through SiOAl chemical bonds. This work puts forward scientific viewpoints and novel design concepts to create effective anti‐corrosion coatings to protect Al alloys, and then expand its potential applications in other fields.

Comparison of the effects of pre-activators on morphology and corrosion resistance of phosphate conversion coating on magnesium alloy

• The effects of three pre-activators (colloidal Ti, oxalic acid, phosphoric acid) on the performance of a PCC was compared. • The pre-activators promote nucleation by peeling off the original oxide film and increasing the specific surface area. • Different pre-activators did not alter the formation mechanism, but significantly changed the growth rate and morphology. • Phosphoric acid was the overall best choice for pre-activating the Mg alloy considering on the PCC performance and cost. In this study, Mg–6.0Zn–3.0Sn–0.5Mn (ZTM630) magnesium alloy was pre-activated by colloidal Ti, oxalic acid, and phosphoric acid, and a phosphate conversion coating (PCC) was prepared on the alloy surface. The morphology and corrosion resistance of the prepared PCCs were investigated. Surface morphology studies showed that the phosphate crystals that formed the coating were the smallest for the sample pre-activated by phosphoric acid. The coating on the colloidal Ti and the phosphoric acid samples had the largest and the smallest thickness and surface roughness, respectively. The reason for the discrepancy was analyzed by comparing the surface morphologies of alloy samples immediately after the pre-activation treatment and various phosphating treatments. X-ray diffraction analysis revealed that all three PCCs contained the same compounds. The corrosion resistance time from the copper sulfate drop test and the electrochemical data from the potentiodynamic polarization curves showed that the coating pre-activated by phosphoric acid had the best corrosion resistance. Finally, the 1500 h neutral salt spray corrosion test confirmed that the phosphating treated magnesium alloy, which was pre-activated by phosphoric acid, exhibited excellent corrosion resistance and behavior.

Study on surface characteristics and stochastic model of corroded steel in neutral salt spray environment

To study the surface morphology characteristic of corroded steel in a neutral salt spray environment, an artificial accelerated corrosion tests were carried out and eight batches of specimens with different corrosion ages were obtained. The corroded steel surface morphologies were collected by a non-contact 3D profiler, and the characteristic parameters were extracted by a special analysis program. The results showed that the corrosion depth of steel surfaces generally follows a normal distribution, while the pit depth and aspect ratio follow a lognormal distribution. As the degree of corrosion increases, the average value and standard deviation of corrosion depth, and logarithm mean value of the pit depth increase, while the logarithm mean value of the pit aspect ratio decreases. In addition, the pit density fluctuates in the range of 20–30 and the conical pits on the steel surface account for the largest proportion in the neutral salt spray corrosion environment. Based on the statistical results and parameter change laws, the stochastic field model of corrosion depth and the random distribution model of corrosion pit were established, and the corroded surfaces were reconstructed in the neutral salt spray corrosion environment.

Microstructure and Corrosion Behavior of Cold-Sprayed Zn-Al Composite Coating

A Zn–Al composite coating was successfully deposited on Q235 steel by cold spray technology for the corrosion protection in the marine atmosphere. The microstructure and corrosion behavior of the prepared coating was studied byScanning Electron Microscope (SEM), X-ray Diffraction (XRD), salt spray test and electrochemical experiments. A 2400-h neutral salt spray corrosion test (with a corrosion medium of 3.5% sodium chloride solution) showed that the prepared cold-sprayed Zn-Al composite coating has excellent anti-corrosion properties. Based on the microstructure evolution and corrosion products analysis, droplets’ flow-driven ‘synergistic corrosion effect’ was proposed to explain the co-corrosion behavior of Zn and Al particles in the composite coating.

Effects of Cr content on corrosion behaviour and corrosion products of spring steels

Neutral salt spray corrosion experiments of spring steels with different Cr contents were carried out for different corrosion periods. The optical microscope was used to observe the macroscopic corrosion morphology of the steel surface. The corrosion pit morphology of steel surface was observed by laser scanning confocal microscopy and scanning electron microscopy, and three-dimensional simulation was carried out. At the same time, the corrosion products (rust layer) were qualitatively and quantitatively analysed by X-ray diffraction. As the results show, Cr is beneficial to improving corrosion resistance of the experimental steel matrix, and the higher the content of Cr, the stronger the corrosion resistance will be. With increase in Cr content in steel, the development of corrosion process will be more effectively suppressed. With the increase in Cr content, the denser the corrosion products, the stronger the bond with the metal matrix is. The corrosion products have obvious stratification; the outer layer is mainly composed of γ-FeOOH, which is relatively loose and not firmly integrated with the matrix, while the inner layer contains α-FeOOH and Fe3O4, which are relatively dense and closely integrated with the matrix. The types of corrosion are constantly changing during different phases of corrosion.