Coated Aluminum Alloy Research Articles

Nondestructive differential eddy current testing for corrosion detection on coated aluminium alloys

Purpose The objective of this study is to use non-destructive testing of corrosion on coated aluminium alloys using differential eddy current detection (DECD), with the aim of elucidating the relationship between the characteristics of corrosion defects and the detection signal. Design/methodology/approach Pitting corrosion defects of varying geometrical dimensions were fabricated on the surface of aluminium alloy plates, and their impedance signals were detected using DECD to investigate the influence of defect diameter, depth, corrosion products and coating thickness on the detection signals. Furthermore, finite element analysis was used to ascertain the eddy current distributions and detection signals under different parameters. Findings The size of the defect is positively correlated with the strength of the detection signal, with the defect affecting the latter by modifying the distribution and magnitude of the eddy current. An increase in the diameter and depth of corrosion defects will enhance the eddy current detection (ECD) signal. The presence of corrosion products in the corrosion defects has no significant effect on the eddy current signal. The presence of a coating results in a decrease in the ECD signal, with the magnitude of this decrease increasing with the thickness of the coating. Originality/value The objective is to provide experimental and theoretical references for the design of eddy current non-destructive testing equipment and eddy current testing applications.

Robust ZIF-8 based superhydrophobic coating with anti-icing, anti-corrosion, and substrate universality

The design of superhydrophobic materials based on zeolite imidazolate frameworks (ZIF) has attracted considerable attention due to their exceptional chemical stability, high specific surface area, and environmental friendliness. However, research in the fields of anti-corrosion and anti-icing remains in its infancy, and the mechanical stability of reported ZIF-based superhydrophobic surfaces is generally poor. In this study, we synthesized ZIF-8@PDA materials in an aqueous system and followed with stearic acid (STA) modification to achieve low surface energy, resulting in ZIF-8@PDA@STA. Subsequently, we applied a spray-coating method to sequentially construct WPU and ZIF-8@PDA@STA layer on aluminum alloy substrates, achieving a ZIF-8@PDA@STA/WPU superhydrophobic coating with exceptional mechanical stability. This coating retained its superhydrophobicity even after 5600 cm of abrasion distance. Furthermore, results from surface wettability, electrochemical and anti-icing tests demonstrated that the coated aluminum alloy exhibited excellent interfacial non-wetting, self-cleaning, anti-fouling, and significantly enhanced corrosion resistance and delayed icing properties. Additionally, the facile preparation of this coating on various substrates facilitates the large-scale application of such materials. The construction of this multifunctional ZIF-8 based superhydrophobic coating is expected to greatly expand the application of ZIF materials across diverse fields.

Protective properties of chromate-free conversion coatings for copper-containing aluminum alloys in tropical climates

Protective properties of chromate-free conversion coatings for copper-containing aluminum alloys in tropical climates

Study of the Synergistic Influence of Plasma Electrolytic Oxidation and Wet Post-Treatment on the Surface of AA7075.

In this study, we enhanced the corrosion and microbial resistance of aluminum 7075 alloys by applying a thin layer of alumina through plasma electrolytic oxidation (PEO) in an alkali-silicate electrolyte. In addition, the influence of film sealing on coated aluminum alloy 7075 was studied in detail, specifically in oil and water at 100 °C after treatment. The surface and cross-sectional morphology, element composition, and phase composition of the PEO coatings were characterized by using scanning electron microscopy (SEM) assisted with energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD), respectively. The corrosion resistance of the coating on AA7075 PEO was evaluated before and after post-treatment using hot water and hump oil at 100 °C. This assessment was conducted by using various electrochemical techniques, including open-circuit potential (OCP), linear polarization resistance (LPR), potentiodynamic polarization scan (PD), electrochemical impedance spectroscopy (EIS), and cyclic potentiodynamic scan (CPS). The results showed that the corrosion resistance of the AA7075 alloy was significantly improved after the PEO coating. The AA7075 + SF, among all of the examined alloys, exhibited superior corrosion properties, due to its fat sealing. This is probably due to the formation of a mixed fatty acid layer from oil on the surface of the AA7075 PEO, which synthesizes a hydrophobic layer. Interestingly, the samples treated with PEO showed a great resistance to microbial growth.

Microstructure and Corrosion Study on Friction Surfaced Aluminum Alloy Coatings over Mild Steel

In this study, the low-carbon steel (AISI 1018 mild steel) substrate is coated with the aluminum alloys AA6082-T6, Al-20Zn, and Al-2Si-15SiC to improve its corrosion resistance by the friction surfacing (FS) technique. To produce a high-quality coating, friction surfacing process variables including spin speed, speed of travel, and the rate of feed are crucial. This experiment examines twelve friction-surfaced plates with different parameter combinations. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) examinations were carried out in order to comprehend the microstructure and chemical composition of the coating deposits and the area in contact between the coated surface and the substrate. Microstructure investigation reveals that the intermetallic combination of Fe-Al at the coating interface region is an effect of the elemental diffusion of Fe to aluminum at the contact interface. Then a uniform and fine-grained coating deposit is observed as a result of the continuous recrystallization of the consumable rod under frictional stress and heat generation. According to the outcomes of the microhardness test, the coated surface is roughly 15–16% harder than the consumable rod. The coating bond strength was measured using a ram tensile test, and it ranged from 102 MPa to 135 MPa. Finally, evaluation of corrosion behavior through immersion testing and pitting corrosion testing reveals that the coatings made of Al-20Zn and Al-2Si-15SiC exhibit good corrosive resistance in an alkaline environment.

Innovative multifunctional nanocomposite coated aluminum alloy for improved mechanical, flame retardant, and corrosion resistance in automobile industries

ABSTRACT Nanocomposites with impermeable two-dimensional materials show promise for metal corrosion protection. A coating matrix incorporating (3-aminopropyl)trimethoxysilane (AMS) functionalized molybdenum nitride (Mo2N) enhances the barrier effect due to its chemical and thermal stability. Further improvement is achieved by adding functionalized Mo2N into graphitic carbon nitride (GCN) within a polyurethane (PU) matrix, enhancing corrosion protection and fire retardancy. Electrochemical techniques evaluated the efficacy of aluminium coated with PU and varying concentrations of functionalized Mo2N/GCN. The resulting PU composite exhibited superior flame retardant capabilities, reducing peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Electrochemical impedance spectroscopy (EIS) showed enhanced coating resistance (5.55 × 101 1 Ω.cm2) even after 500 hours of exposure. Additionally, the composite displayed exceptional water repellency with a water contact angle (WCA) of 156° and commendable mechanical properties, including an adhesive strength of 19.2 MPa within the PU substrate. This multifunctional PU composite, incorporating functionalized Mo2N/GCN, presents a promising option for automotive coatings, offering corrosion protection, flame retardancy, water repellency, and mechanical robustness, thus enhancing durability and performance in harsh conditions.

Chelating agent stimulated LDH post-treatment of PEO coated AA2024

Layered double hydroxides (LDHs) are well known and broadly investigated on bare aluminum alloys, but not on PEO treated aluminum where source of aluminum ions is restricted. The additions of the chelating agents were tested in this work to stimulate the LDH formation on PEO (plasma electrolytic oxidation) coated aluminum alloy AA2024. 1,3-diamino-2-hydroxipropane-N,N,N’,N’-tetraacetic acid (DHPTA) was identified as the most effective one among tested additives. Its performance in terms of LDH growth stimulation was investigated. The DHPTA additive provides an increase of the pH of the LDH synthesis compared to previously known methods to achieve hydration of aluminum oxide from PEO as the initial stage of PEO etching, as well as the formation of soluble complex compounds of Zn-DHPTA, necessary for the formation of ZnAl LDH. The process of LDH formation was also followed by intercalation of DHPTA ions into LDH galleries. It was shown that LDH was formed both on the surface and insight the pores of parental PEO coating. Moreover, it imparted lubricating properties to the hybrid coating. Finally, PEO-LDH coating demonstrated higher corrosion resistance and long-term stability comparing to the PEO coated aluminum alloy.

Influence of heating temperature and time on mechanical-degradation, microstructures and corrosion performances of Teflon/granite coated aluminum alloys used for non-stick cookware

This study explores the functional characteristics (erosion, corrosion, mechanical damage, and microstructural features) of non-stick cookware made from aluminum alloys. Typically coated with polytetrafluoroethylene (PTFE-Teflon) or ceramic for non-stick properties, we conducted a systematic investigation using corrosion, abrasion, and mechanical tests on six types of cookware from different manufacturers (Manuf-1-6). The cookware was heated at various temperatures [Room temperature (RT), 100, 175, 250, & 350 °C] and times (45 & 120 min). Tests included Taber wear, Adhesive Pull-off, hot & RT corrosion, and surface roughness measurements. Characterization involved optical microscopy, scanning electron microscope (SEM) with electron backscattered diffraction (EBSD), and x-ray diffraction (XRD). Ceramic-coated cookware from Manuf-4 demonstrated superior mechanical strength, wear, and corrosion resistance due to refined microstructures. Manuf-1's PTFE-coated cookware also performed well. Optimal results were observed when heating below 250 °C for up to 45 min. Prolonged heating and temperatures beyond 250 °C adversely affected internal structures of all cookware. Thus, it is advisable to use Al-based non-stick cookware below 250 °C for a maximum of 45 min.

Investigation on microstructure and wear resistance of WC coated aluminum alloy using machine hammer peening

Due to the characteristic of low density and high strength, Aluminum alloy have been applied in various industries. However, poor surface properties, such as wear resistance, are the main reason for limiting its application. In this study, machine hammer peening (MHP) was used for embedding tungsten carbide (WC) particles in near-surface zone of aluminum alloy and the microstructure and wear resistance were investigated. The results show that WC particles can be embedded into aluminum alloy using MHP and WC coatings were generated with large and medium WC particles. The values of surface roughness were increased with increasing of WC particles sizes and XRD analysis indicated that no new compound was found during coating process. The significant increasing of wear resistance of WC coating has been obtained. MHP is a novel technique for obtaining WC coating and improving the tribological performance of aluminum alloy. Furthermore, it offers new possibilities to embedding hard particles in substrates of various materials.

Effect of hydrogen embrittlement on the tribo-mechanical properties of TiN coated aluminium alloys

ABSTRACT In this research, the effects on tribological properties of titanium nitride (TiN) coating by hydrogen embrittlement were investigated. TiN was deposited to about 2.5 μm on aluminium alloy by arc ion plating (AIP). Hydrogen embrittlement was conducted for 3 and 6 h to investigate the dependence of wear properties of the TiN coating on hydrogen embrittlement time. As the hydrogen embrittlement time increased, the surface hardness and the adhesive force with the substrate decreased due to the peeling of the coating. In a ball on disk wear experiment, the hydrogen embrittlement specimens showed an increase in coefficient of friction due to the debris generated by the peeling of the TiN coating. In the 3 h hydrogen embrittlement specimen, the wear track was locally damaged. However, the 6 h hydrogen embrittlement specimen showed that the aluminium base material was exposed while the wear track was damaged as a whole.

Infrared-responsive shape memory self-healing and fluorescent damage-indication anti-corrosion coatings for aluminum alloys

Infrared-responsive shape memory self-healing and fluorescent damage-indication anti-corrosion coatings for aluminum alloys

Extremely improved the corrosion resistance and anti-wear behavior of aluminum alloy in 3.5% NaCl solution via amorphous CrAlN coating protection

The low hardness and limited anti-wear of aluminum alloys pose obstacles to their stability and service life, especially in corrosive environments. Here, the amorphous CrAlN coating was first deposited on aluminum alloy by DC magnetron sputtering. The CrAlN coating with 30.2% nitrogen content was dense and prevented the intrusion of oxidation and corrosive fluids, thus greatly improving the anti-corrosion of the coating. The wear rate of the coated aluminum alloy in 3.5% NaCl solution decreased by three orders of magnitude. This work paves the way for constructing amorphous protective coatings on light alloys.

Shoulder-Restricted Friction Deposition for Aluminum Alloy Coatings on Titanium Alloys

In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to roughen the titanium substrate, the process verification of Al deposition onto TC4 was realized. The material utilization was close to 100%, and a deposition layer with a thickness of 0.8 mm and a strong bonded interface was obtained. The peel strength of the triple-layer deposited joints was 121 MPa.

Quantitative study of the effect of high-performance zinc alloy coating technology on the life of mechanical components

Abstract Corrosion of mechanical components has been of wide interest in recent decades. Corrosion is caused by physicochemical action between a metal and its environment, which can result in changes in the metal’s properties and functional damage in mechanical components. The main corrosion manifestations of zinc alloy coatings in marine environments are discussed in this paper, which first explores the application of high-performance aluminum alloy coatings in industry. Subsequently, the ZAS35 alloy used for this paper was experimentally prepared, and orthogonal tests were utilized to determine the optimum matching values of process parameters for zinc alloy coatings to generate materials. The hardness and wear resistance of ZAS35 were evaluated against other zinc alloys. An iterative learning control algorithm was employed to determine the thickness of the zinc alloy coating. The optimal control of the steady-state process of coating thickness can be achieved by using the NARX dynamic neural network model as a predictive identification model for zinc alloy coating thickness. Finally, data were collected using an optical microscope to quantitatively analyze the effect of zinc alloy plating on mechanical life. When the thickness of zinc alloy is 1.7 μm, the probability of life is [947.56,978.36]×103h interval t=0.999, which is improved by 409~684.11×103h compared with the plating thickness of 1.10μm . After adding aluminum elements to zinc plating, the corrosion potential of the plating decreases from −800mV to −1000mV, and the zinc-aluminum alloy prevents electrochemical corrosion of the plated layer with cathodic corrosion inhibition.

Al-20Si/Cu-8P high‑silicon aluminum alloy coating enhanced by laser remelting and refinement: Microstructure, mechanical properties and wear resistance

An Al-20Si/Cu-8P high‑silicon aluminum alloy coating was prepared on A356 aluminum alloy by plasma spraying and was remelted by laser technology subsequently. Whereupon, the microstructure, mechanical properties and wear resistance of the coating before and after remelting were comparatively studied, aiming to investigated the combined enhancement effect of remelting and refining on high‑silicon aluminum alloy coatings. The results showed that the laser remelting basically eliminated the defects in the sprayed coating, and produced a metallurgical bonding interface between the coating and the substrate. The microstructure of the coatings before and after remelting was both composed of primary silicon and eutectic structure (α-Al + Si). Nevertheless, the Cu8P dissolved more fully and dispersed more evenly in the remelted coating, which was conducive to fully utilizing its refinement effect on primary silicon. Thus, the primary silicon in the remelted coating was obviously reduced in size compared with that in the sprayed coating, and its distribution was more even. Accordingly, the hardness, elastic modulus and fracture toughness of the remelted coating were greatly enhanced compared with the sprayed coating. Under dry friction condition, the wear resistance of the two coatings was significantly superior to that of the substrate. Compared with the sprayed coating, the friction coefficient of the remelted coating was slightly smaller, and the wear volume was reduced by 33.1 %. Therefore, the microstructure of Al-20Si/Cu-8P high‑silicon aluminum alloy coating was significantly improved and its properties was obviously enhanced by laser remelting and refinement.

Effect of coating thickness on microstructural and mechanical properties of titanium coated aluminum alloy deposited by vacuum arc melting method

This study aims to investigate the effects of titanium coatings on aluminum alloy’s tribological and fatigue properties. In this investigation, aluminum alloy samples were coated with 1 μm, 3 μm, and 5 μm using the vacuum arc melting method. The morphological and mechanical features of the samples were characterized with SEM, microhardness, contact nanoprofilometer, and calotest methods. The increase in coating thickness resulted in improved adhesion properties and achieved better surface hardness. Further, hard sub-surface layers on the aluminum alloy substrate increased fatigue resistance. The superior mechanical properties, such as microhardness, lower surface roughness, and good bonding at the interface, are critical factors in increasing the fatigue and wear resistance of the aluminum alloy. No traces of defects, such as microcracks and porosity, were found on the coated samples. The microhardness of the coated sample increased by 3.69 times that of the AK5M2 aluminum alloy. The fatigue lifetime of the 5 μm coated samples was increased by 21%. The wear resistance of titanium-coated samples showed better wear resistance against the steel counter body than other coated and uncoated samples.

Study on the Influence of Surface Treatment Process on the Corrosion Resistance of Aluminum Alloy Profile Coating.

This work focuses on different surface treatment processes of the 6061 aluminum alloy profile coatings in the construction industry, mainly including the sand powder film coating, the flat powder coating, the hard anodized film, and the ordinary heat-sealing oxidized coating. The corrosion resistance of the coated aluminum alloy in a 3.5 wt.% NaCl solution (pH 6.5-7.5) and the influence of different surface treatment processes on the corrosion resistance of different samples were studied by scanning electron microscope (SEM) and electrochemical workstation. The result shows that with the increase in corrosion time, the corrosion inhibition performance of the four coated aluminum alloy materials decreased significantly, and the order of decline is: sand powder film coating > hard anodized film > flat powder coating > ordinary heat-sealing oxidized coating. When corroded in a 3.5 wt.% NaCl solution for 2 h, the corrosion inhibition performances of the flat powder coating and ordinary heat-sealing oxidized coating are poor, while the inhibition performances of the sand powder film coating and hard anodized film are good, and the inhibition performance follows the following sequence: the sand powder film coating > hard anodized film> the flat powder coating > ordinary heat-sealing oxidized coating. When corroded in a 3.5 wt.% NaCl solution for 200 h, the corrosion inhibition performances of the sand powder film coating and the flat powder coating are poor, while the inhibition performances of hard anodized film and ordinary heat-sealing oxidized coating are good, and the inhibition performance follows the following sequence: hard anodized film > ordinary heat-sealing oxidized coating > the sand powder film coating > the flat powder coating.

Interplay between Anodizing Parameters and Corrosion Resistance of Aluminum-Silicon Alloys

Aluminum alloys are widely used in the automotive, aerospace and construction fields due to their excellent physico-mechanical properties. Nevertheless, the corrosion resistance of bare Al alloys is often insufficient to meet the requirements of several industrial applications and protection strategies are needed. Among these, anodizing is particularly effective since it can lead to the formation of a compact and thick dielectric oxide layer with barrier and corrosion protection capabilities.However, anodizing of highly alloyed Aluminum alloys (e.g. those with an alloy element concentration higher than 5%wt) can be particularly challenging due to the presence of intermetallic precipitates within the Al matrix which generates micro-galvanic coupling events with an associated thickness inhomogeneity of the obtained anodic layer [1].In this context, the work investigates ten new current waveforms for anodizing of Aluminum Silicon alloys (AlSix). Particular attention is devoted to the interplay among waveform parameters (e.g. duty cycle, peak and rest step intensities), oxide layer morphology and corrosion resistance. In particular, metallography, voltammetry and contact angle methods are used in order to correlate different figures of merit with the anodic layer morphological features.It is concluded that a careful optimization of the current waveform parameters can modulate the: a) corrosion current; b) corrosion potential; c) breakdown potential; and d) polarization resistance; of coated specimens. In conclusion, the most effective waveforms are identified and coated Aluminum alloy specimens with a remarkable corrosion resistance are obtained.[1] M Bandiera, A Bonfanti, M Bestetti, F Bertasi, SAE International Journal of Advances and Current Practices in Mobility 3 (2), 973-979.

Microstructure and surface hardness of ceramic composite coated aluminium alloy

A ceramic composite coating of Cr2O3 + TiC was developed on the surface of Al-6061 alloy plates. The HVOF coating process depends on the parameters such as substrate temperature, powder gas carrier flow rate, pressure, feed rate, standoff distance, and angle between the torch and substrate. The evaluation of surface hardness and microstructure ceramic composite coatings are discussed in this paper. Surface hardness was tested using the Nano-Indentation Tester. The microstructural characterization was conducted using Scanning Electron Microscope (SEM). The hardness test was conducted with a maximum load of 60 mN. The results indicated a vast improvement in the surface hardness of both the coated specimens. The tests performed indicated that Cr2O3 + 10%TiC coatings had a higher average hardness and modulus of elasticity measured at 4.33 GPa, and 108 GPa respectively. Whereas TiC + 10%Cr2O3 indicated a lower hardness and modulus of elasticity measured at 1.62 GPa and 79 GPa respectively. Thus, the tests showed that the Cr2O3 + 10%TiC coatings were harder. The microstructural characterization was conducted using the SEM for both cross sectional view and top view. The microstructural images indicated that the TiC + 10%Cr2O3 coated samples had a better surface finish, as compared to the Cr2O3 + 10%TiC coated samples.

Effect of heat treatment on the microstructure and mechanical properties of 7075 aluminum alloy cold-spray coatings

Cold Spray (CS) exhibit unique features due to the low temperatures involved. However, the CS coating are harder than the corresponding powders and bulk alloys, which results in a low toughness and then greatly limits the application of CS. To overcome this shortage, preheat treatment of powder and post-heat treatment of CS coating are applied to improve the performance of cold-sprayed 7075 aluminum alloy coatings in this work. With increasing temperatures of post-heat treatment, the tensile strength of the coatings increased from 228 MPa to 309 MPa with elongation of 2.46%. Microstructure analysis of the heat-treated coatings revealed that the improvement in mechanical properties was primarily due to an increase in the secondary phase. Accordingly, 7075 aluminum alloy powder was preheat treated at 200 °C and then used for cold spraying, which resulted in improved mechanical properties in the resultant coatings exhibiting a tensile strength of 302 MPa and an elongation of 3.87%. These findings provide valuable insights into the practical application of cold-spraying technology in the aviation field.