Corrosion Behaviors of the Eutectic Structure in Zn-Al-Mg Alloy Coated Steel in Chloride Containing Aqueous Environment

To clearly understand the effect of the eutectic structure in the Zn-Al-Mg alloy coating on the corrosion behaviors in chloride containing aqueous environments, a bulk Zn-MgZn2 sample was fabricated by diffusion bonding process, and a variety of experiments, such as electrochemical polarization and galvanic corrosion measurements, salt spray tests, and cyclic corrosion tests, were carried out. This study revealed that the corrosion potential values of MgZn2 and Zn samples exposed to a 5 wt.% of NaCl solution were approximately -1.5 and -1 VSCE, respectively, and the MgZn2 showed a higher corrosion current density than Zn at the early stage of corrosion. The continued dissolution of MgZn2 phase from the eutectic structure in the coating layer provides not only sacrificial protection, but also environmental conditions for the co-formation of two types of corrosion products (simonkoleite (Zn5(OH)8Cl2·H2O) and hydrotalcite (ZnAl2(OH)6Cl2·H2O)) which have an inhibiting effect on the outer surface. The formation areas and kinetics of the two products on the coating surface were different, and they were greatly dependent upon the types of eutectic structures in the coating layer. Based on the results, a modified anti-corrosion mechanism of Zn-Al-Mg alloy coated steel sheet in chloride containing aqueous environment was proposed.

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Pitting corrosion and crevice corrosion behaviors of titanium alloy overlapped with aluminized PVC film in neutral salt spray

Corrosion Reviews ◽

10.1515/corrrev-2020-0070 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Longfei Xie ◽

Wenlong Zhou ◽

Shiwen Zou ◽

Xuesong Fu

Keyword(s):

Crevice Corrosion ◽

Graphical Model ◽

Electrochemical Impedance ◽

Galvanic Corrosion ◽

Salt Spray ◽

Corrosion Mechanism ◽

Neutral Salt ◽

X Ray ◽

Pvc Film ◽

Corrosion Behaviors

Abstract This paper presents a research on the corrosion behavior of Ti-15-3 alloy overlapped with aluminized PVC film in salt spray. It was found that severe corrosion occurred on aluminized PVC film in the coupled regions because of crevice corrosion and/or galvanic corrosion whereas Ti-15-3 alloy in the coupled regions experienced minor corrosion. Scanning electron microscope and Energy-dispersive X-ray spectroscopy analyses demonstrated the corrosion products adhered to the surface of Ti-15-3 alloy within the crevice. To evaluate the effect of aluminized PVC film on the crevice corrosion of Ti-15-3 alloy in salt spray condition, it is necessary to compare with the corrosion resistance of Ti-15-3 overlapped with polytetrafluoroethylene (PTFE) in different neutral salt spray. Further, the tests were performed by electrochemical impedance spectroscopy and potentiodynamic polarization. Combining the graphical model, an in-depth understanding of the crevice and galvanic corrosion mechanism of Ti-15-3 alloy overlapped with aluminized PVC film has been revealed.

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The Corrosion Mechanism of Zn-5%Al-0.3%Mg Coating

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.1284 ◽

2011 ◽

Vol 189-193 ◽

pp. 1284-1287

Author(s):

Bo Gao ◽

Shi Wei Li ◽

Yi Hao ◽

Gan Feng Tu ◽

Liang Hu ◽

...

Keyword(s):

Corrosion Resistance ◽

Salt Spray ◽

Alloy Coating ◽

Mg Alloy ◽

Corrosion Mechanism ◽

Neutral Salt ◽

Test Results ◽

Crystal Boundary ◽

Cold Rolled ◽

Al Coating

A new hot dip Zn-5%Al-0.3%Mg alloy coating was performed on cold rolled common steel. The hot-dip process was executed by self-made hot dip galvanising simulator (China patent, No.201010160353). The corrosion resistance of alloy-coated steels was detected by neutral salt spray test . SEM and EDS test results demonstrate that Mg is mainly distributed in the crystal boundary. XRD test results shows corrosion product of Zn-5%Al-0.3%Mg alloy coating is mainly Zn5(OH)8Cl2•H2O. The characteristic of Zn5 (OH)8Cl2•H2O is dense and insoluble, so it is protective. In order to study the anticorrosion mechanism, all the tests of the Zn-5%Al-0.3%Mg alloy were carried out with Zn-5%Al coating together.

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Corrosion Initiation Behavior of Thermal Control Oxidation Film of LA103Z Alloy

Frontiers in Materials ◽

10.3389/fmats.2021.717663 ◽

2021 ◽

Vol 8 ◽

Author(s):

Chen Wen ◽

Jingying Bai ◽

Kuo Zhao ◽

Qingxin Cui ◽

Baocheng Jiao ◽

...

Keyword(s):

Early Stage ◽

Thermal Control ◽

Sample Surface ◽

Treatment Method ◽

Chemical Oxidation ◽

Corrosion Mechanism ◽

Electrochemical Characteristics ◽

Corrosion Initiation ◽

Corrosion Behaviors ◽

Last Stage

The magnesium lithium thermal control oxidation is a commonly used conductive anti-corrosion treatment method for aerospace. The corrosion behaviors of thermal control oxidation films for LA103Z alloys were studied in 3.5% NaCl solution. The corrosion characteristics with different immersion time were characterized by using scanning electron microscopy, energy spectroscopy, and electrochemical methods. The results showed that the corrosion of Mg-Li alloy with chemical oxidation film starts from pitting corrosion, gradually expands in depth in the early stage, forms corrosion holes, and then gradually develops into river-like morphology. In the last stage, the increasing corrosion products slow down the corrosion rate and gradually covers the entire sample surface. The corrosion product mainly consists of MgO, LiF, and MgCl2. Combined with the electrochemical characteristics, the corrosion mechanism was investigated.

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Mitigation of Galvanic Corrosion in Bolted Joint of AZ31B and Carbon Fiber-Reinforced Composite Using Polymer Insulation

Materials ◽

10.3390/ma14071670 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1670

Author(s):

Jiheon Jun ◽

Yong Lim ◽

Yuan Li ◽

Charles Warren ◽

Zhili Feng

Keyword(s):

Carbon Fiber ◽

Galvanic Corrosion ◽

Salt Spray ◽

Bolted Joints ◽

Fiber Reinforced ◽

Cross Sectional ◽

Fiber Reinforced Composite ◽

Reinforced Composite ◽

Corrosion Behaviors ◽

Carbon Fiber Reinforced

The use of polymer insulation to mitigate galvanic corrosion was examined for bolted joints of AZ31B Mg alloy and carbon fiber-reinforced composite. To assess the corrosion behaviors of bolted joints with and without polymer insulation, solution immersion and salt spray exposure (ASTM B117) tests were conducted, and the corrosion depths and volumes were determined for the joint specimens after the tests. The polymer-insulated bolted joints exhibited much lower corrosion depths and volumes, highlighting the effective mitigation of galvanic corrosion. The reductions of joint strength in the post-corrosion joint specimens were relatively small (up to ~10%) in the polymer-insulated group but greater (up to 90%) in the group with no insulation. Cross-sectional characterization of post-corrosion joints with polymer insulation revealed local pits developed on AZ31B under galvanic influence, indicating that limited galvanic attack (that did not decrease the joining integrity significantly) could still occur during a long salt spray exposure (~1264 h) owing to the permeation of an aqueous corrosive medium.

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Corrosion Behaviour of Lead-Free and Sn-Pb Solders in 3.5wt% NaCl

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.686.250 ◽

2013 ◽

Vol 686 ◽

pp. 250-260 ◽

Cited By ~ 3

Author(s):

Asma Kamarul Asri ◽

Esah Hamzah

Keyword(s):

Sodium Chloride ◽

Corrosion Behaviour ◽

Galvanic Corrosion ◽

Salt Spray ◽

Lead Free ◽

Corrosion Mechanism ◽

Corrosion Tests ◽

Lead Free Solders ◽

Better Than

The current need to produce lead-free solders in the electronic industries makes it necessary for the replacing solders to have properties which are comparable if not better than the conventional Sn-Pb solders. Thus this research was conducted to compare the corrosion behaviour of lead-free solders with composition Sn-4.0Ag-0.5Cu (SAC405), and Sn-3.0Ag-0.5Cu (SAC305) with conventional Sn-37Pb solders. Corrosion tests were conducted using salt spray tests with 3.5% sodium chloride (NaCl) solutions. The samples were characterized after corrosion tests by using SEM, EDS and XRD. The results showed that the elements present in the solders contributed to galvanic corrosion mechanism that affected the overall corrosion behaviour of the solders.

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A PROPOSAL FOR MODIFIED GALVANIC CORROSION MODEL: INVESTIGATING EFFECTS OF MICRO-ARC OXIDATION ON Al ALLOY

Surface Review and Letters ◽

10.1142/s0218625x18501470 ◽

2019 ◽

Vol 26 (02) ◽

pp. 1850147

Author(s):

YUANHANG YANG ◽

YANHONG GU ◽

JIAN LIANG ◽

WEN YUE

Keyword(s):

Open Circuit Potential ◽

Galvanic Corrosion ◽

Open Circuit ◽

Al Alloy ◽

Corrosion Mechanism ◽

Corrosion Performance ◽

Before And After ◽

Micro Arc Oxidation ◽

Corrosion Behaviors ◽

Micro Structures

Corrosion is generally an undesirable phenomenon in most engineering applications. The effects of micro-arc oxidation (MAO) coating on Al alloy on the galvanic corrosion performance have been studied. The surface micro-structures were characterized using scanning electron microscope (SEM) and metallographic microscope before and after corrosion. Electrochemical studies on the corrosion behaviors have been reported by using open circuit potential (OCP) and potentiodynamic polarization (PDP) measurements in a slurry solution. All measurements were consistent with each other and showed that the MAO coating can significantly reduce the corrosion rate of Al alloy. A model for elucidating corrosion mechanism and corrosion process of the MAO coating on Al alloy is proposed.

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Comparison On The Immersion Corrosion and Electrochemical Performance of WC-Al2O3 Composites and WC-Co Hard Metal in NaCl Solution

10.21203/rs.3.rs-376939/v1 ◽

2021 ◽

Author(s):

Bin Han ◽

Weiwei Dong ◽

Bowen Fan ◽

Shigen Zhu

Keyword(s):

Hard Alloy ◽

Galvanic Corrosion ◽

Hard Metal ◽

Electrochemical Technique ◽

Corrosion Mechanism ◽

Nacl Solution ◽

Passivation Film ◽

Immersion Corrosion ◽

Corrosion Behaviors ◽

Hot Pressing Sintering

Abstract WC-15wt.%Al2O3 composites was prepared via hot pressing sintering technology. The corrosion behaviors of WC-Al2O3 composites and traditional WC-Co hard alloy in NaCl solution were studied by immersion corrosion and electrochemical technique. The impedance value of WC-Al2O3 composite increased more rapidly than WC-Co hard metal during the 24 hours, which indicated that WC-Al2O3 composites has more compact passivation film than WC-Co hard metal. The results confirmed that the corrosion performance of WC-Al2O3 composites was higher than WC-Co cemented carbide in NaCl solution. The corrosion mechanism of WC-Al2O3 composites and WC-Co hard alloy in NaCl solution were also revealed by SEM, EDS, XPS and Raman. The corrosion products of WC-Al2O3 composites mainly contain WO3, while for WC-Co hard alloy are Co (OH)2, Co3O4 and WO3. The different corrosion mechanism of the two materials is attributed to the Al2O3 phase instead of the Co binder, which avoids the galvanic corrosion between WC phase and Co binder.

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