Formation Of Corrosion Products Research Articles

Structure and corrosion properties of multilayer metal/nitride/oxide ceramic coatings formed on austenitic-martensitic steel by magnetron deposition

The design of protective coatings preventing the degradation and failure of austenitic steels in humid climate is a relevant issue. In this work, a conventional magnetron sputtering method was utilized in order to fabricate a four-layer Ni/Al-Si-N/Ni/Al-Si-O coating onto austenitic-martensitic steel. At the first stage of deposition, a three-layer coating was formed in an Ar+N2 atmosphere using a mosaic target (Ni or Al-Si), while the second stage included the deposition of the outer ceramic Al-Si-O layer in an Ar+O2 gas mixture. The studies of the structure, hardness, adhesion strength and electrochemical behavior (in 3.5 wt. % NaCl) of the «coating/steel» system were performed by means of X-ray Diffraction, electron microscopy, mechanical (indentation and scratch) tests and electrochemical impedance spectroscopy. The ceramic Al-Si-O layer exhibits an amorphous structure. The adjacent nickel layers have submicrocrystalline columnar grains. The ceramic Al-Si-N layer possesses a nanocrystalline columnar structure based on AlN + Si3N4 phases. Hardness behavior of the multilayer coating varies nonmonotonically due to a contribution of the soft amorphous phase in the upper surface layer and high-strength nanocrystalline phases in the underlying sublayers. It has been revealed that as-deposited multilayer coating decreases a corrosion rate of the substrate. The layered structure of the coating hinders the transport and diffusion of chloride ions to the substrate and decreases the corrosion rate of the substrate. However, a transport of chloride ions into the inner layers of the coating may occur through the microstructural defects preserved in the amorphous Al-Si-O layer. The scheme describing an initiation of corrosion damage and formation of corrosion products under critical corrosion conditions was proposed.

Self-Healing Phenomenon at the Cut Edge of Zn-Al-Mg Alloy Coated Steel in Chloride Environments

This study explores the self-healing phenomenon at the cut edges of Zn-Al-Mg alloy coated steel in chloride environments, a critical consideration for materials exposed to marine conditions. Zn-Al-Mg coatings offer superior resistance to cut-edge corrosion. This research aims to unravel the self-healing properties observed in these coatings. Through cyclic corrosion tests (CCTs), we compared the corrosion resistance of Zn-Al-Mg coated steel with traditional zinc alloy coatings. Our findings show a notable reduction in corrosion with ZMA4 coatings after 120 CCT cycles. This is due to the formation of corrosion products, namely layered double hydroxides (LDHs) and Mg(OH)2. X-ray diffraction and X-ray photoelectron spectroscopy analyses were employed to confirm the presence of these products and elucidate their roles in the self-healing process. This study highlights the potential of Zn-Al-Mg coatings for enhancing the durability of steel structures in corrosive environments, suggesting a paradigm shift in corrosion protection strategies for marine applications. The development of coatings that exhibit self-healing capabilities in chloride-rich environments could significantly mitigate the challenges posed by cut-edge corrosion, promising extended service life and reduced maintenance costs.

Influence of hydrogen sulphide on the corrosion and hydrogenation of 07Cr16Ni6 steel

The effect of hydrogen sulphide concentration on the corrosion behaviour of 07Cr16Ni6 austenitic-martensitic stainless steel in a 5% NaCl + 0.5% CH3COOH solution was studied to determine the role of H2S in the corrosion product formation and corrosion mechanism. Unstable passivation of steel is detected in a solution containing <100 mg/dm3 H2S. Steel corrodes in an electrochemically active state at >100 mg/dm3 H2S. When the pitting potential is reached, pitting damage occurs at the grain boundaries. The corrosion rate decreases by ∼five times after exposition for 720 h due to the formation of nickel and iron sulphides on the surface. Corrosion is accompanied by the absorption of 4.2–17.5 ppm hydrogen, 62…70% of which is diffusible and can cause hydrogen embrittlement. The scheme of steel corrosion under the influence of different concentrations of hydrogen sulphide is proposed.

Degradation of thiocyanate by Fe/Cu/C microelectrolysis: Role of pre-magnetization and enhancement mechanism

Thiocyanate (SCN−), a non-volatile inorganic pollutant, is commonly found in various types of industrial wastewater, which is resistant to hydrolysis and has the potential to be toxic to organisms. Premagnetized iron-copper-carbon ternary micro-electrolytic filler (pre-Fe/Cu/C) was prepared to degrade SCN−. Pre-Fe/Cu/C exhibited the most significant enhancement effect on SCN− removal when magnetized for 5 min with an intensity of 100 mT, and the SCN− removal rate was the highest at an initial pH of 3.0 and an aeration rate of 1.6 L/min. The electrochemical corrosion and electron transfer in the pre-Fe/Cu/C system were confirmed through SEM, XPS, FTIR, XRD, and electrochemical tests. This resulted in the formation of more corrosion products and multiple cycles of Fe2+/Fe3+ and Cu0/Cu+/Cu2+. Additionally, density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) were utilized to illustrate the oxygen adsorption properties of the materials and the participation of reactive oxygen species (1O2, ·O2−, and ·OH) in SCN− removal. The degradation products of SCN− were identified as SO42−, HCO3−, NH4+, and N2. This study introduced the use of permanent magnets for the first time to enhance Fe/Cu/C ternary micro-electrolytic fillers, offering a cost-effective, versatile, and stable approach that effectively effectively enhanced the degradation of SCN−.

Effect of ionic liquids on the corrosion behaviour of X80 pipeline steel

The study encompasses the synthesis of an ionic liquid corrosion inhibitor using the ion exchange method. Its impact on the corrosion and hydrogen permeation behaviour of X80 pipeline steel in a CO2 environment is thoroughly investigated. The findings reveal that the corrosion resistance and hydrogen atom diffusion of X80 pipeline steel exhibit an initial decline, followed by an increase with escalating inhibitor concentration. The nadir values are recorded at an inhibitor concentration of 500 mg·L−1, attaining a remarkable maximum inhibition efficiency of 97%. Following the addition of corrosion inhibitors, the formation of corrosion products notably decreases, indicating a positive inhibition effect on both corrosion and hydrogen permeation. Additionally, a correlation is successfully established between hydrogen permeation parameters and inhibitor concentration.

Degradation of RC Columns under Combined Exposure to Axial Loading, Stray Currents, and Chloride Ingress.

Coastal regions, home to a significant portion of the world's population, confront a formidable challenge: the corrosive impact of chloride-rich environments on vital infrastructure. These areas often host essential transportation systems, such as trains and metros, reliant on pre-existing electrical infrastructure. Unfortunately, complete isolation of this infrastructure is rarely feasible, resulting in the emergence of stray currents and electrical potentials that expedite corrosion processes. When coupled with conducive mediums facilitating chemical electrocell formation, the corrosion of reinforced concrete elements accelerates significantly. To combat this issue, international standards have been established, primarily focusing on augmenting the thickness of reinforcement bar covers and restricting stray voltage between rails and the ground. Nevertheless, these measures only provide partial solutions. When subjected to service loads, these elements develop cracks, especially when exposed to stray currents and chlorides, dramatically increasing corrosion rates. Corrosion products, which expand in volume compared to steel, exert internal forces that widen cracks, hastening the deterioration of structural elements. The study deals with the degradation of reinforced concrete columns under the combined action of loads, chloride-rich environments, and electrical voltage-simulating stray currents. In these conditions, degradation and reduction of load-bearing capacity accelerate compared to unloaded conditions, significantly amplifying the corrosion rate. Astonishingly, even in the absence of mechanical loads, stray currents alone induce tensile stresses in elements due to corrosion product formation, leading to longitudinal cracks parallel to the reinforcement bars.

Fabrication and characterization of zirconium oxide coating on tubular steel by metal organic decomposition

In fusion reactor blankets, multifunctional ceramic coatings fabricated on structural materials have been investigated for tritium permeation reduction, electrical insulation, and corrosion protection. However, it has been challenging to manufacture a homogeneous coating on the complicated components in the blanket breeder, such as ducts. In terms of sustainable development, it is crucial to establish a ceramic coating technique on the inner walls of fuel pipes in liquid blanket systems. In this study, we applied the metal organic decomposition method to fabricate zirconium oxide coatings on 316L austenitic stainless steel tubes and characterized their properties as liquid tritium breeding pipes. Homogeneous zirconium oxide coatings with a thickness of 395 ± 12 nm have formed on the inner walls of SS316L tubes. The compatibility of the coated tubes with liquid lithium-lead was examined under static and flowing conditions at 550–600 °C for prolonged exposure of up to 2000 h. Under static conditions, ZrO2 coatings demonstrated exceptional compatibility with the liquid Li-Pb as they protected structural material from corrosion. At a flow rate of 0.16 m/s, the coatings were partly delaminated due to different thermal expansion coefficients of the coating and substrate and acceleration under a dynamic system. The coating thickness increased up to 650 ± 26 nm after exposure for 2000 h, which indicated ZrO2 coatings reacted with Li-Pb to form corrosion products. Besides, ZrO2 coatings achieved the insulating requirements of magnetohydrodynamic insulators as their electrical resistivities were on the order of 104–106 Ω m at the temperature range of 250–550 °C.

Corrosion Behavior of Zn-Al-Mg-Si Coatings in Sulfur Dioxide-Containing Environment

Zn-Al-Mg-Si coatings are an excellent alternative to conventional hot-dip galvanizing coatings. Their high corrosion resistance in corrosive environments containing chlorides and CO2 is well recognized. But sulfur dioxide is also an important stimulator of corrosion in the atmospheric environment. This article presents the results of microstructure (SEM/EDS/XRD) and corrosion behavior tests of Zn-Al-Mg-Si coatings obtained by a double hot-dip method on HSLA steel. The corrosion resistance of the coatings was determined in the sulfur dioxide test with general condensation of moisture (EN ISO 6988). In the corrosion test, Zn-Al-Mg-Si coatings showed twofold smaller weight loss compared to conventional hot-dip zinc coatings. It was found that the corrosion behavior of coatings was influenced by the structural components revealed in the outer layer: Al-rich dendritic and interdendritic areas with Zn/MgZn2 eutectic, MgZn2 intermetallic and Si precipitates and their electrochemical nature. The increase in corrosion resistance was caused by the formation of beneficial corrosion products: layered double hydroxides (LDHs) based on divalent Mg2+ and Zn2+ cations, trivalent Al3+ cations and SO42− anions, and zinc hydroxysulfate—Zn4SO4(OH)6∙5H2O. The presence of Si precipitates could cause pitting corrosion of coatings.

Research on the construction of gradient nanostructure and anti-tribocorrosion behavior of aluminum alloy surface

Gradient nanostructure in aluminum alloy, constructed via a two-dimensional ultrasonic surface burnishing process, displays enhanced tribocorrosion resistance in artificial seawater. Corrosion tests are undertaken to understand the influence of gradient nanostructure on corrosion resistance, and crystal plasticity finite element models are developed to examine wear resistance. Tribocorrosion tests are performed through wear tests in the artificial seawater environment. The results indicate that the processed samples' corrosion rate decreases from 3.12 × 10−2 mm/a to 2.45 × 10−3 mm/a. The wear scar sizes of the processed samples are approximately half the unprocessed samples. The gradient nanostructure obstructs dislocation glide during wear, diminishes the accumulation shear, and promotes high-hardness corrosion product formation, effectively isolating the direct contact between the friction pairs, thus improving the tribocorrosion resistance.

Research on the evolution of corrosion products of 17-4 PH martensitic stainless steel in the tropical marine environment

Deterioration of stainless steel is significantly influenced by the characteristics of corrosion products. Evolution of corrosion products of 17-4 PH martensitic stainless steel (17-4 PH MSS) in the tropical marine environment was systematically studied by field-exposure, combined with morphological observation, compositional characterization and electrochemical testing in this work. The corrosion process of 17-4 PH MSS was divided into three stages: stage I–rapid formation and shedding of corrosion products, stage II–adhesion and transformation of corrosion products and stage Ⅲ–remarkable increase in the protective properties of corrosion products. Corrosion rate of 17-4 PH MSS was maximum in the first stage and then decreased continuously in the second and third stages, which is closely related to the morphology, distribution and composition of the corrosion products. In terms of morphological evolution, corrosion products of 17-4 PH MSS showed the dynamic cycle characteristic of "nucleation-growth-cracking-shedding". In view of compositional transformation, the high content of Cr, Ni, and Cu in stainless steel is involved in the formation of corrosion products, and the production of Cr2O3, Cr(OH)3, FeCr2O4, NiFe2O4, and CuFeO2 after 6 months of exposure was an important shift. Argument from protective properties, increase in coverage percentage and the generation of Cr-containing products are responsible for the enhancement of protective properties of the corrosion products. This work prepares the way for further research on the generation and growth mechanism of pitting under corrosion products and provides technical support for the design, selection, and protection of stainless steel in tropical marine environments.

Characterization of corrosion products formed on Q235 carbon steel and T2 copper in the Antarctic atmosphere

This study delves into the intricate corrosion behavior of ferrous and non-ferrous alloys in the challenging Antarctic marine atmosphere. Despite the harsh conditions and exceptionally low anthropogenic emissions in Antarctica, materials are still susceptible to severe corrosion. The investigation focuses on two materials: Q235 carbon steel and T2 copper. Both display distinct corrosion cases between their skyward and groundward sides due to the abrasive impact of persistent strong winds carrying ice particles and grit. Electrochemical reactions at the anode and cathode drive surface corrosion processes, involving Cl− and SO42−, ultimately leading to the formation of various corrosion products. The study highlights the role of sulfur-containing aerosols, Methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO42-) in corrosion processes, as well as the interaction between Cl− and copper in forming corrosion products. The findings emphasize the complex interplay of environmental factors like wind, ice cover, and aerosols with materials, leading to diverse corrosion products and surface transformations. Further research is crucial to gain a comprehensive understanding of corrosion challenges in extreme environments like Antarctica and to develop effective mitigation strategies.

Influence of Cr(III) on the formation and transformation of corrosion products of steel in marine environments

A fundamental approach is used to better understand the influence of Cr on the resistance of low alloy steel to marine corrosion. It focuses on the formation and transformation of corrosion products of steel in seawater-like electrolytes. Fe(OH)2 precipitates are then prepared by mixing a solution of NaCl, Na2SO4·10H2O, FeCl2·4H2O or FeCl2·4H2O + CrCl3·6H2O (so that Cr = 8% and Fe = 92%), with a solution of NaOH. The initial concentration ratio of reactants, Q=frac{2[{{{rm{Fe}}}}^{2+}]+3[{{{rm{Cr}}}}^{3+}]}{[{{{rm{OH}}}}^{-}]}, is set at Q = 0.88, 1, and 1.136. In a first approach, the obtained aqueous suspension is stirred, at a controlled temperature of 25 ± 0.5 °C, to be oxidized by air. The resulting oxidation product is characterized by XRD and Raman spectroscopy. In a second approach, the Fe(OH)2 precipitates are aged one week in suspension in anoxic conditions, filtered, mixed as a wet paste with glycerol and set as a thin compact layer on the sample holder of a X-ray diffraction system. The oxidation process of Fe(OH)2 is then monitored in situ during the acquisition of the X-ray diffractogram. The obtained results demonstrate that Cr(III) hinders the formation of green rust compounds, hence hindering the formation of γ-FeOOH, i.e., the main oxidation product of green rust compounds. The other oxidation pathways of Fe(OH)2, which lead to Fe3O4 or α-FeOOH, are thus favored. Nevertheless, Cr(III) favors mainly the solid state transformation pathway of Fe(OH)2, thus promoting α-FeOOH via the formation of poorly ordered Fe(III) oxyhydroxides, namely feroxyhyte and ferrihydrite.

Enhanced corrosion resistance of epoxy resin coating via addition of CeO2 and benzotriazole

The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied. In this work, CeO2 and Benzotriazole (BTA) were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel. SEM results indicated that the CeO2 grains were rod-like and ellipsoidal in shape, and the distribution pattern of BTA was analyzed by EDS. The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO2 and BTA co-addition; and electrochemical impedance spectroscopy test (EIS) analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating. And the optimal protective performance was provided by the coating containing 0.3 wt.% CeO2 and 20 wt.% BTA, which attributed to the barrier performance of CeO2 particles and chemical barrier effect of BTA. The formation of corrosion products was analyzed using XRD. In addition, the corrosion resistance mechanism of the coating was also discussed in detail.

Monitoring Atmospheric Corrosion of Carbon Steel Under Controlled Electrolyte Droplet Distributions

Field exposure testing and accelerated corrosion testing are two common approaches applied in the industry to assess the atmospheric corrosion rate of a specific material, both relying on visual inspection and weight change of the specimen. Field exposure testing occurs under natural atmospheric conditions but requires exposure times spanning decades, whereas accelerated corrosion testing shortens the exposure time to weeks; however, the connection between the natural environment and accelerated corrosion chamber conditions remains unresolved. Efforts have been made to correlate accelerated corrosion results with those obtained in field exposure based on weight loss, both qualitatively and quantitatively, primarily empirically and limited to small datasets.This work examines the link between modified field exposure testing and the environment from the electrolyte perspective, under controlled laboratory conditions. In-situ monitoring and analysis of corrosion rate, electrolyte condition, and environment are demonstrated to be feasible, and the effect of NaCl concentration and droplet distribution on the atmospheric corrosion rate of carbon steel has been addressed.This work proposes a setup wherein multiple droplet-based conditions are created, and corrosion kinetics are actively monitored using the electrical resistance method. The sample surface is simultaneously monitored with an optical microscope, through which both droplet distribution evolution and corrosion product formation can be visualized.

Material Selection for Fundamental Investigation of High Temperature Processes in Lithium-Ion Cathode Production

Rapid upscaling of current and near-future lithium-ion battery (LIB) technologies is one of the main remaining challenges for road transport electrification. Among cathode materials high-Ni layered lithium transition metal oxides, Li(NixCoyMn1-x-y)O2 (LNMC, x ≥ 0.7), show large potential for application in next-generation LIB’s because of their high energy density, low cost, and superior electrochemical properties 1–3.To optimize current cathode production technologies, and to select the most optimal future technologies, a thorough understanding of the synthesis fundamentals of lithium-ion cathode calcination processes is a prerequisite. In this context, in-situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have emerged as powerful tools for investigating the high-temperature reaction mechanism of the synthesis of these materials 4,5. However, most research does not address some challenges that come with studying complex high temperature synthesis reactions at the inherit small scale of these in-situ techniques. One issue, is that detailed information on the materials used for supporting the samples is seldomly mentioned, making it difficult to distinguish possible side reactions from the main reactions occurring during high temperature characterization. In only a limited number of studies on the high temperature interaction between ternary lithium-ion battery cathode materials and common substrate materials, evidence of direct contact-corrosion of refractory materials due to lithium compounds has been observed 6. To obtain meaningful insights from these in-situ techniques on the synthesis mechanism of LIB cathode materials that are transferable to mass production processes, these unwanted side reactions must be avoided as much as possible.The purpose of the current study is to select the optimal support material for high temperature in-situ characterization of LIB calcination processes. Several LNMC blends, containing a Li compound and a NMC precursor, were calcined in different crucible materials under a 100% O2 flow at 900 °C for 10-12 hours. The selected crucibles for this investigation include common oxide refractories: Al2O3, SiO2 (fiber and quartz) and MgO, as well as Au, as a frequently used inert material for lab scale experiments. Chemical composition of the precursor blend and calcined products are compared by inductively coupled plasma optical emission spectroscopy ICP-OES. Additionally, weight increase of each crucible material is tracked over multiple calcination cycles, and the formed corrosion products are characterized with SEM-EDS and XRD. The ICP-OES measurements show that the final Li:TM ratio of the calcined LNMC material is heavily influenced by the used crucible material, indicating that selecting an appropriate support material is crucial to avoid side reactions and thus ensure that small scale in situ characterization methods such as in-situ XRD and TGA provide relevant data. Nitta, N., Wu, F., Lee, J.T. & Yushin, G. Mater. Today 18, 252–264 (2015).Schipper, F. et al. J. Electrochem. Soc. 164, A6220–A6228 (2017).Julien, C.M. & Mauger, A. Energies 13, 6363 (2020).Wang, D. et al. Adv. Mater. 29, 1606715 (2017).Gao, M. et al. Ionics 27, 3729–3737 (2021).Zhai, P. et al. J. Eur. Ceram. Soc. 38, 2145–2151 (2018).

Ionic Liquid Initiated Corrosion Products on Steel

Ionic liquids (ILs ) are achieving great interest as electrically addressable lubricants. The demands of lubrication of inaccessible systems, such as wind turbines, coupled with the lubrication paradigm shift engendered by electric vehicles makes IL lubricant additives extremely attractive. The interaction of ILs with steel surfaces and initiation of corrosion need to be urgently addressed, since ILs are in principle organic salts, and water is ubiquitous , even at ppm levels. In this study we have applied a set of surface sensitive advanced techniques, such as Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Confocal Raman Microscopy, Nano-IR and FTIR microscopy as well as scattering GISAXS, to investigate the formed corrosion products in tribo films containing designer ionic liquids at steel surfaces. The trihexyl-(tetradecyl)phosphonium-bis(oxalato)borate [P6,6,6,14][BOB] ionic liquid and a specially deposited AISI 52100 steel were used in this study. The IL breakdown and various surface-formed corrosion products were imaged and analyzed. The formation of iron oxides and various borate and phosphate-containing products, and their interrelation, is observed and mechanistically discussed.

Electrochemical corrosion and high temperature hot corrosion behavior of NbTaTiV and CrNbTaTiV high entropy alloy

NbTaTiV and CrNbTaTiV were fabricated by arc melting and effect of Cr element on electrochemical and high temperature hot corrosion behavior were compared. Electrochemical corrosion investigations revealed that Laves phase at grain boundaries of CrNbTaTiV would underwent galvanic corrosion, resulting in a marginal reduction in corrosion resistance. The results of high temperature hot corrosion showed that within Na2SO4 + 25 wt% NaCl molten salt environment, the oxide film formed by Cr element effectively improved the surface stability, reduced the formation of unprotected loose corrosion products and the generation of low melting point chlorides with strong volatility, which improved the resistance of molten salt corrosion.

Application of cathodic protection method on steel structures using sacrificial anode and sodium polyacrylate-sodium carboxymethyl cellulose (PANa–CMC) hydrogel electrolyte

An ionically conductive sodium polyacrylate-sodium carboxymethyl cellulose (PANa–CMC) hydrogel electrolyte was developed for the sacrificial anode cathodic protection (SACP) of carbon steel in high-humidity environments. The incorporation of varying ratios of CMC into hydrogel formulation enhanced the water retention capacity, adhesion strength, and electrochemical performance, making it suitable for SACP applications. Particularly, PANa-5% CMC hydrogels demonstrated a current density of approximately 3 μA/cm², inhibited passive corrosion product formation, and sequestered metal ions from anodes, thus minimizing contamination. These findings highlight the substantial potential of PANa–CMC hydrogels as electrolytes, expanding the application of the SACP method to atmospheric environments.

Comparative study of the effects of galvanic corrosion on the strength and the failure of aluminium and stainless steel bolted joints

This paper investigates the effects of bimetallic insert on corrosion, material degradation, loading capacity, stress distribution, strain distribution and failure of aluminium-stainless steel lap shear bolted assemblies. The single bolt lap shear assemblies of aluminium and stainless steel plates were performed in two settings in one of them a bimetallic insert was used. Considering that the aluminium plays the role of sacrificial anode in the aluminium-stainless steel galvanic couple, a single bolt lap shear assembly joining two aluminium plates is also considered as a reference. The experimental measurements were determined by tensile-shear testing method for three different conditions: dry condition and two corrosion states corresponding to 6 weeks and 16 weeks of accelerated corrosion tests. To support understanding of the effects of preload and friction changes due to the formation of corrosion products, finite element simulations were performed with varying preloads and friction coefficients. The study demonstrated significant effects of corrosion on loading capacity, bolt rotation and failure mode. The tensile-shear forces measured for the aluminium-aluminium assembly and aluminium-stainless steel assembly after 6 weeks of accelerated corrosion tests increased compared to the tensile-shear forces measured in dry condition. The increase in tensile-shear forces was related to the formation of corrosion products, affecting the preload and the frictional behaviour of the contacting surfaces. In agreement with experimental observations, finite element simulations demonstrated an increase in the tensile-shear force with the increase of frictional forces. The application of bimetallic inserts considerably reduces the effect of corrosion on the measured tensile-shear force of corroded assembly compared to non-corroded assembly. However, it affects the force-displacement response and failure mode compared to the response of aluminium-stainless steel assembly without bimetallic insert due to its effects on the bolt rotation and stress distribution. This needs to be considered in the design of dissimilar material bolted assembly.

Initial dissolution of Mg-containing phase and corrosion product formation in cut-edge corrosion of Zn-11%Al-3%Mg-0.2%Si coated steel

Simulated cut-edge specimens of Zn-11%Al-3%Mg-0.2%Si coated steel were fabricated, and their corrosion behaviors were assessed using salt spray test (SST). The Mg-containing phases in the coating near the simulated cut-edge dissolved during early corrosion, leading to the formation of protective corrosion products on the steel surface. The corrosion products suppressed the oxygen reduction reaction on the steel. Additionally, the anodic dissolution rate of the coating layer decreased after the SST. Consequently, the cut-edge corrosion rate of the Zn-Al-Mg coating after the deposition of the corrosion products decreased compared with that of a conventional Zn coating.