scholarly journals Galvanic Corrosion Between Coated Al Alloy Plate and Stainless Steel Fasteners, Part 1: FEM Model Development and Validation

CORROSION ◽  
10.5006/3308 ◽  
2019 ◽  
Vol 75 (12) ◽  
pp. 1461-1473 ◽  
Author(s):  
R.S. Marshall ◽  
R.G. Kelly ◽  
A. Goff ◽  
C. Sprinkle
Keyword(s):  
Aluminum Alloy ◽  
Experimental Test ◽  
Galvanic Corrosion ◽  
Corrosion Damage ◽  
Geometric Constraints ◽  
Al Alloy ◽  
Worst Case ◽  
Alloy Plate ◽  
Fastener Hole ◽  
Galvanic Couples

Aerospace structures often involve dissimilar materials to optimize structural performance and cost. These materials can then lead to the formation of galvanic couples when moisture is present. Specifically, noble metal fasteners (such as SS316) are often used in aluminum alloy load-bearing structures, which can lead to accelerated, localized corrosion attack of the aluminum alloy due to the cathodic current supplied by the SS316 fastener. This localized attack is difficult to predict, and tests are often expensive, so modeling of these galvanic couples could be of great utility. The work reported here focuses on the galvanic coupling between fasteners installed in a panel test assembly, and the resultant corrosion damage down the fastener holes. This arrangement is a common assembly geometry in aerospace applications. A specific sol-gel coating was applied to the fasteners, to determine its effectiveness on mitigating galvanic corrosion; bare fasteners were also tested, to investigate a worst-case scenario. Geometric constraints in the model were made to match those of an experimental test panel, which was exposed to ASTM B117 salt fog for 504 h. The electrochemical boundary conditions were generated in solutions appropriate to the material and environment to which it would be exposed. Anodic charge passed during exposure was calculated from image analyses of the corrosion damage in the experimental test, and the results were compared with the model. The Laplacian-based model provides a very good first approximation for predicting the damage within the fastener hole. Validation was provided by both experimental results generated in this study as well as comparison to results in the literature that used similar, but not identical, conditions.

scholarly journals Corrosion Monitoring Method of Porous Aluminum Alloy Plate Hole Edges Based on Piezoelectric Sensors

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1106 ◽  
Author(s):  
Wei Dai ◽  
Xiangyu Wang ◽  
Meng Zhang ◽  
Weifang Zhang ◽  
Rongqiao Wang
Keyword(s):  
Aluminum Alloy ◽  
Corrosion Damage ◽  
Reconstruction Algorithm ◽  
Piezoelectric Sensors ◽  
Corrosion Monitoring ◽  
Monitoring Method ◽  
Alloy Plate ◽  
Porous Aluminum ◽  
Stress Concentration Region ◽  
Aluminum Alloy Plate

Corrosion damage to the aircraft structure can significantly reduce the safety performance and endanger flight safety. Especially when the corrosion occurs in a stress concentration region, such as hole edges, it can easily threaten the entire structure. In this paper, an on-line imaging qualitative monitoring algorithm based on piezoelectric sensors is proposed for detecting hole edge corrosion damage of porous aluminum alloy structures. The normalized amplitude is used to characterize the correlation between the initial Lamb wave signal and the damage signal, which is as an image reconstruction parameter in the algebraic iterative probability reconstruction algorithm. Moreover, a homogenization algorithm is proposed to process the reconstruction results. The experimental results of single hole and double hole corrosion for porous aluminum alloy plate show that the method can effectively achieve the location and quantification of corrosion damage to one and two holes of the porous structure.

scholarly journals Numerical Investigation on the Effects of Circuit Parameters on the Plastic Deformation of Fastener Holes in Thin Aluminum Alloy via Electromagnetic Expansion Process

2021 ◽  
Author(s):  
Xiaofei Xu ◽  
Huihui Geng ◽  
Qingshan Cao ◽  
Quanliang Cao ◽  
Liang Li ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Deformation Zone ◽  
Plastic Deformation Zone ◽  
Strengthening Effect ◽  
Expansion Process ◽  
Alloy Plate ◽  
Hole Expansion ◽  
Discharge Capacitance ◽  
Fastener Hole

Abstract The size of plastic deformation zone during fastener hole strengthening is a critical indicator of the strengthening effect. In this study, a considerable plastic deformation zone in 1.5 mm aluminum alloy plate with a hole was produced via electromagnetic strengthening. The finite element analysis results showed that the electromagnetic strengthening process could achieve high compressive hoop residual stress around the fastener hole in thin plate without serious axial deformation compared with conventional cold hole expansion process. The simulation results were experimentally validated by the grid method. Furthermore, for the same discharge energy, the size of plastic deformation zone varies with the discharge capacitance, and there was an optimal combination of the discharge capacitance and discharge voltage. What’s more, even the plastic deformation zone was the same at the maxed load, different unloading process during the electromagnetic hole expansion process also had a great influence on the strengthening effect.

Corrosion of Aluminized Steel in Seawater

2004 ◽  
Author(s):  
Hiroki Kimoto
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Flow Rate ◽  
Galvanic Corrosion ◽  
Al Alloy ◽  
Corrosion Rates ◽  
Aluminized Steel ◽  
Alloy Carbon ◽  
Galvanic Couples

The influence of flow rate of seawater on the corrosion rate of hot-dipped aluminized steel in seawater was investigated using the following galvanic couples: aluminum/carbon steel, aluminum/Fe-Al alloy, aluminum/stainless steel, Fe-Al alloy/carbon steel, Fe-Al alloy/stainless steel, and carbon steel/stainless steel. The corrosion rate of aluminum in all the couples was greater than that of aluminum not connected with other metals. The corrosion rates increased in the following order: aluminum/carbon steel > aluminum/stainless steel > aluminum/Fe-Al alloy. Aluminum connected with carbon steel had the greatest corrosion rate: seven times of the rate of aluminum that was not connected with other metals. The galvanic corrosion rate of carbon steel is 1.9 to 2.5 times greater than that of carbon steel that is not connected with other metals.

Corrosion Behavior of Twin-Wire Metal Inert Gas Arc Welds in 7A52 Al Alloy Plate

2011 ◽  
Vol 314-316 ◽  
pp. 918-922
Author(s):  
Xi Wei Zhai ◽  
Fu Rong Chen ◽  
Rui Ling Jia ◽  
Xiao Dong Wang
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Inert Gas ◽  
Al Alloy ◽  
Alloy Plate ◽  
Welding Joint ◽  
Tandem Welding ◽  
7A52 Aluminum Alloy

Abstract. 7A52 aluminum alloy plate was welded using twin-wire metal inert gas arc welding (TANDEM welding). Corrosion behavior of the welded joint was investigated by immersion in 3.5% NaCl solution. Scanning electron microscopy (SEM) and electrochemical inspections, specifically, polarization curves and electrochemical impedance spectroscopy (EIS), were conducted to understand corrosion behavior of the TANDEM welding joint of 7A52 aluminum alloy. It was found that the heat affected zone (HAZ) exhibited higher corrosion susceptibility than the weld beam (WB), fusion zone (FZ) and base metal (BM). The electrochemical results showed that the WB with higher corrosion potential and larger impedance had highest corrosion resistance. Variations in the composition and grain size might have led to the differences in corrosion resistance because the welding process influenced microstructures of the TANDEM welding joint of 7A52 aluminum.

Galvanic Corrosion Behavior and Three Protection Techniques of Magnesium Alloy Coupled to A6N01S-T5 Aluminum Alloy in NaCl Solution

2011 ◽  
Vol 686 ◽  
pp. 146-150
Author(s):  
Ding Fei Zhang ◽  
Yu Ping Liu ◽  
Chang Guo Chen ◽  
Ya Juan Xu
Keyword(s):  
Aluminum Alloy ◽  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Galvanic Corrosion ◽  
Open Circuit ◽  
Al Alloy ◽  
Nacl Solution ◽  
Immersion Method ◽  
Coating Technique ◽  
Mobile Industry

In this work, the galvanic corrosion behavior of AZ31 magnesium alloy in contact with A6N01S-T5 aluminum alloy in NaCl solution was investigated by electrochemical method, the salt immersion method, SEM. And three protection techniques: (a) rubber gasket technique ,(b)organic coating technique and (c) anodizing technique were used to inhibit the galvanic corrosion. The results of open circuit potential and polarization curve method were explained the corrosion behavior of AZ31 and A6N01S-T5.It was found that AZ31 as anode was accelerated corrosion and A6N01S-T5 as cathode was also corrode in salt immersion experiment. With the increasing of immersion time, the corrosion rate of AZ31 and A6N01S-T5 was gradually decreasing. Then, the efficacy of different anti-corrosive technologies was compared. Fluorine coating technique was an effective way to protect Mg alloy and Al alloy. It was possible to guide the anti-corrosion of magnesium alloy in mobile industry.

Development of corrosion flaws for the production of realistic test specimens

2020 ◽  
Vol 64 (1) ◽  
pp. 23-28
Author(s):  
J. Hodač ◽  
Z. Fulín ◽  
P. Mareš ◽  
J. Veselá ◽  
O. Chocholatý
Keyword(s):  
Power Plants ◽  
Galvanic Corrosion ◽  
Water Solution ◽  
Erosive Wear ◽  
Corrosion Damage ◽  
Water Mist ◽  
Carbon Steels ◽  
Bending Stress ◽  
Solution Flow ◽  
Mechanical Bending

AbstractTo produce realistic test specimens with realistic flaws, it is necessary to develop appropriate procedure for corrosion flaw production. Tested specimens are made from steels commonly used in power plants, such as carbon steels, stainless steels and their dissimilar weldments. In this study, corrosion damage from NaCl water solution and NaCl water mist are compared. Specimens were tested with and without mechanical bending stress. The corrosion processes produced plane, pitting and galvanic corrosion. On dissimilar weldments galvanic corrosion was observed and resulted to the deepest corrosion damage. Deepest corrosion flaws were formed on welded samples. The corrosion rate was also affected by the solution flow in a contact with the specimens, which results in a corrosion-erosive wear. Produced flaws are suitable as natural crack initiators or as realistic corrosion flaws in test specimens.

scholarly journals A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 491
Author(s):  
Alina E. Kozhukhova ◽  
Stephanus P. du Preez ◽  
Aleksander A. Malakhov ◽  
Dmitri G. Bessarabov
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Combustion Temperature ◽  
Volume Fraction ◽  
Morphological Characteristics ◽  
Al Alloy ◽  
Impregnation Method ◽  
Case Scenario ◽  
Worst Case ◽  
Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

scholarly journals Effect of Laser Power on Microstructure and Micro-Galvanic Corrosion Behavior of a 6061-T6 Aluminum Alloy Welding Joints

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 3
Author(s):  
Huiling Zhou ◽  
Fanglian Fu ◽  
Zhixin Dai ◽  
Yanxin Qiao ◽  
Jian Chen ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Laser Power ◽  
Galvanic Corrosion ◽  
Gas Metal Arc Welding ◽  
Immersion Test ◽  
Intermetallic Particles ◽  
Metal Arc Welding ◽  
Corrosion Behaviors ◽  
Welding Joints ◽  
Corrosion Pits

The 6061-T6 aluminum alloy welding joints were fabricated using gas metal arc welding (GMAW) of various laser powers, and the effect of laser power on the microstructure evolution of the welding joints was investigated. The corrosion behaviors of 6061-T6 aluminum alloy welding joints were investigated in 3.5 wt% NaCl solution using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the micro-galvanic corrosion initiation from Mg2Si or around the intermetallic particles (Al-Fe-Si) is observed after the immersion test due to the inhomogeneous nature of the microstructure. The preferential dissolution of the Mg2Si and Al-Fe-Si is believed to be the possible cause of pitting corrosion. When the laser power reached 5 kW, the microstructure of the welded joint mainly consisted of Al-Fe-Si rather than the Mg2Si at 2 kW. The relatively higher content of Al-Fe-Si with increasing in laser power would increase the volume of corrosion pits.

Gold Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy and Three-Dimensional Contour Imaging of an Aluminum Alloy

2020 ◽  
pp. 000370282097304
Author(s):  
Amal A. Khedr ◽  
Mahmoud A. Sliem ◽  
Mohamed Abdel-Harith
Keyword(s):  
Gold Nanoparticles ◽  
Aluminum Alloy ◽  
Three Dimensional ◽  
Plasma Temperature ◽  
Spectral Lines ◽  
Laser Induced Breakdown Spectroscopy ◽  
Al Alloy ◽  
Boltzmann Plot ◽  
Breakdown Spectroscopy ◽  
Laser Induced Breakdown

In the present work, nanoparticle-enhanced laser-induced breakdown spectroscopy was used to analyze an aluminum alloy. Although LIBS has numerous advantages, it suffers from low sensitivity and low detection limits compared to other spectrochemical analytical methods. However, using gold nanoparticles helps to overcome such drawbacks and enhances the LIBS sensitivity in analyzing aluminum alloy in the current work. Aluminum was the major element in the analyzed samples (99.9%), while magnesium (Mg) was the minor element (0.1%). The spread of gold nanoparticles onto the Al alloy and using a laser with different pulse energies were exploited to enhance the Al alloy spectral lines. The results showed that Au NPs successfully improved the alloy spectral lines intensity by eight times, which could be useful for detecting many trace elements in higher matrix alloys. Under the assumption of local thermodynamic equilibrium, the Boltzmann plot was used to calculate the plasma temperature. Besides, the electron density was calculated using Mg and H lines at Mg(I) at 285.2 nm and Hα(I) at 656.2 nm, respectively. Three-dimensional contour mapping and color fill images contributed to understanding the behavior of the involved effects.

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