Characterizations of UV Aging and Atmospheric Corrosion on Epoxy Coated 7A04 Aluminum Alloy

2011 ◽  
Vol 686 ◽  
pp. 784-791
Author(s):  
Chao Fang Dong ◽  
Kui Xiao ◽  
Hai Sheng ◽  
Y.H. An ◽  
Xiao Gang Li
Keyword(s):  
Aluminum Alloy ◽  
Uv Irradiation ◽  
Atmospheric Corrosion ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Alloy System ◽  
Epoxy Coating ◽  
Test Time ◽  
Uv Aging ◽  
Resistance Decrease

The aim of this work is to investigate characterizations of corrosion on 7A04 aluminum alloy with epoxy coating under simulated marine atmosphere with/without ultraviolet irradiation. The environment containing Cl-and sunlight illumination was simulated by salt spray test and UV irradiation/condensation treatment. The corrosion behavior was studied by electrochemical impedance spectroscopy, and level of coating damage was evaluated through gloss measurement. Scanning electron microscope was chosen to observe surface properties of epoxy coating/7A04 aluminum alloy system. The results show that the electrochemical characters are closely related to the aging degree of epoxy coating, which could influence the penetrating process of oxygen and corrosive medium. The coating resistance decrease, while the coating capacitance and the pore rate increase as prolonging of the test time. Along with gloss loss of epoxy coating, pores appear on the surface and the blisters break, which may act as bulk defects of epoxy coating. The coating degradation and substrate corrosion were accelerated by the cooperation of UV irradiation and salt spray. UV aging significant accelerated the deterioration of coating with larger and deeper pores compared to that of non-UV irradiation coating.

scholarly journals Preparation and Properties of Self-Healing and Self-Lubricating Epoxy Coatings with Polyurethane Microcapsules Containing Bifunctional Linseed Oil

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1578 ◽  
Author(s):  
Haijuan Yang ◽  
Qiufeng Mo ◽  
Weizhou Li ◽  
Fengmei Gu
Keyword(s):  
Interfacial Polymerization ◽  
Electrochemical Impedance ◽  
Linseed Oil ◽  
Salt Spray ◽  
Average Diameter ◽  
Organic Coating ◽  
Epoxy Coating ◽  
The Self ◽  
Self Healing ◽  
Pure Epoxy

An organic coating is commonly used to protect metal from corrosion, but it is prone to failure due to microcracks generated by internal stress and external mechanical action. The self-healing and self-lubricating achieved in the coating is novel, which allows an extension of life by providing resistance to damage and repair after damage. In this study, a new approach to microencapsulating bifunctional linseed oil with polyurethane shell by interfacial polymerization. Moreover, the self-healing and self-lubricating coatings with different concentrations of microcapsules were developed. The well-dispersed microcapsules showed a regular spherical morphology with an average diameter of ~64.9 μm and a core content of 74.0 wt.%. The results of the salt spray test demonstrated that coatings containing microcapsules still possess anticorrosion, which is improved with the increase of microcapsules content, after being scratched. The results of electrochemical impedance spectroscopy showed a |Z|f=0.01Hz value of 104 Ω·cm2 for pure epoxy coating after being immersed for 3 days, whereas the coating with 20 wt.% microcapsules was the highest, 1010 Ω·cm2. The results of friction wear showed that the tribological performance of the coating was enhanced greatly as microcapsule concentration reached 10 wt.% or more, which showed a 86.8% or more reduction in the friction coefficient compared to the pure epoxy coating. These results indicated that the coatings containing microcapsules exhibited excellent self-healing and self-lubricating properties, which are positively correlated with microcapsules content.

scholarly journals ESTUDIO DE LA RESISTENCIA A LA CORROSION DEL ALUMINIO 6063 ANODIZADO

2017 ◽  
Vol 22 (2) ◽  
pp. 17
Author(s):  
Karín Paucar Cuba ◽  
Hugo Rojas Flores ◽  
Abel Vergara Sotomayor
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Sulfuric Acid ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Aluminum Surface ◽  
Equivalent Circuits ◽  
Acid Salt ◽  
Mass Losses ◽  
Palabras Clave

El estudio de la resistencia a la corrosión del anodizado de una aleación de aluminio (AA6063) en ácido sulfúrico a diferentes tiempos de anodizado: 30, 45 y 60 min. se realizó usando la espectroscopia de impedancia electroquímica (EIE) y el ensayo de niebla salina ácida. (ASTM B287). Los datos obtenidos por EIE y su correlación con los circuitos equivalentes más apropiados permitieron determinar los parámetros asociados a la capa porosa y a la capa barrera del óxido protector formado sobre la superficie del aluminio en estudio. La exposición de las muestras anodizadas durante 250h a una niebla salina ácida permitió observar variaciones en su masa. De los resultados obtenidos por EIE y las pérdidas de masa de las muestras anodizadas se estableció que la película de anodizado de 45 minutos mostró una mayor resistencia a la corrosión en comparación con la obtenida a 60 y 30 min., respectivamente. Palabras clave.- Aluminio, Anodizado, Impedancia electroquímica, Niebla salina ácida. ABSTRACTThe study of the corrosion resistance of anodized on aluminum alloy (AA6063) in sulfuric acid to different times: 30, 45 and 60 min. was performed using electrochemical impedance spectroscopy (EIS) and the acid salt spray test (ASTM B287). The EIS’data and its correlation with the most appropriate equivalent circuits allowed to determine the parameters associated with the porous layer and the oxide layer protective barrier formed on the aluminum surface under study. Exposure of the samples anodized for a 250h salt spray acid allowed to observe changes in their mass. From the results obtained by EIS and the mass losses of the anodized samples was established that the anodized film of 45 minutes showed higher corrosion resistance compared to that obtained at 60 and 30 min, respectively. Keywords.- Aluminum, Anodized, Electrochemical impedance, Acid salt spray.

A Comparative Study of Neat Epoxy Coating and NanoZrO2/Epoxy Coating for Corrosion Protection on Carbon Steel

2014 ◽  
Vol 599-601 ◽  
pp. 3-6
Author(s):  
Xia Zhao ◽  
Shuan Liu ◽  
Bao Rong Hou
Keyword(s):  
Carbon Steel ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Epoxy Coating ◽  
Steel Plates ◽  
Neat Epoxy ◽  
Corrosive Media ◽  
Tafel Polarization ◽  
Q235 Carbon Steel

nanoZrO2 was modified by styrene coupling grafting method and then used as an additive to improve the protective performance of epoxy coating. Two kinds of coatings, neat epoxy coating and nanoZrO2/epoxy coating, were prepared and applied on Q235 carbon steel plates. The plates were submitted to salt spray chamber and seawater immersion for 1000 hours to evaluate the corrosion protection performance for these two kinds of coatings. Tafel polarization curves and electrochemical impedance spectroscopy (EIS) were determined to analyze the corrosion behavior of coating/metal system. Scanning electron microscopy (SEM) and photographs were carried out for morphology analysis of two kinds of coatings under different conditions. Results showed a superior stability and efficient corrosion protection by nanoZrO2 /epoxy coating. The modified nanoZrO2 could inhibit the penetration of corrosive media and then improve the corrosion protection of the epoxy coating on carbon steel.

scholarly journals Pore resistance limitations from EIS data for the evaluation of organic DTM coatings based on a self-crosslinking acrylic resin

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
M. Vanegas ◽  
J.J Medina ◽  
L.F. Vesga ◽  
W. Bejarano
Keyword(s):  
Atmospheric Corrosion ◽  
Visual Inspection ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Acrylic Resin ◽  
Point Of View ◽  
Neutral Salt ◽  
Crosslinking Process ◽  
Acrylic Resins ◽  
Coated Surfaces

Self-crosslinking Water-based acrylic resins are currently widely used in the formulation of paints for the protection of materials exposed to atmospheric corrosion. These resins, given their "self-crosslinking" designation, initiate their crosslinking process once they are applied on a previously prepared surface. It is expected that with time they will increase their protection, due to their continuing self-crosslinking mechanism. In this work, metallic plates coated with these resins were evaluated under simulated salt neutral spray (ASTM B117). The coating degradation processes were monitored by Electrochemical Impedance Spectroscopy (EIS) and visual inspection, according to ASTM D610 and ASTM D714, aiming to identify and quantify the appearance of blistering and corrosion products. The results revealed rapid drops in pore resistance (Rpo) for systems exposed to neutral salt spray (NSS), saline-acidic or acidified conditions, which coincided with the formation of blisters. On the contrary, the systems in the wet chamber showed an increase in the Rpo, which evidences from an electrical point of view a greater opposition to the passage of current. Notwithstanding, still the appearance of blisters on the coated surfaces was observed.

Corrosion Protection of Aluminum Alloy 2024-T3 by Vanadate Conversion Coatings

CORROSION ◽  
2004 ◽  
Vol 60 (3) ◽  
pp. 284-296 ◽  
Author(s):  
H. Guan ◽  
R. G. Buchheit
Keyword(s):  
Aluminum Alloy ◽  
Corrosion Protection ◽  
Inductively Coupled Plasma ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Conversion Coating ◽  
Self Healing ◽  
Pitting Potential ◽  
X Ray ◽  
Aluminum Alloy 2024

Abstract In this paper, the formation, chemistry, morphology, and corrosion protection of a new type of inorganic conversion coating is described. This coating, referred to as a vanadate conversion coating (VCC), forms on aluminum alloy substrates in a matter of minutes during simple immersion in aqueous vanadate-based solutions at ambient temperatures. VCCs are yellow in color and conformal across the surface of aluminum alloy 2024-T3 (AA2024-T3 [UNS A92024]) substrates. Auger electron sputter depth profiles and x-ray absorption near-edge spectroscopy show that VCCs formed by a 3-min immersion are 300 nm to 500 nm thick and consist of a mixture of vanadium oxides and other components in the coating bath. In anodic polarization experiments conducted in aerated chloride solutions, VCCs increase the pitting potential and decrease the rate of oxygen reduction. When characterized by electrochemical impedance spectroscopy, VCCs demonstrate a low-frequency impedance between 1 MΩ-cm2 and 2 MΩ-cm2 after 24 h exposure to aerated 0.5 M sodium chloride (NaCl) solutions. In salt spray testing conducted according to ASTM B117, VCCs suppress formation of large pits for more than 168 h. VCCs also appear to be self-healing. Analysis of solution in contact with VCCs by inductively coupled plasma emission spectroscopy indicates that vanadate is released into solution upon exposure. Vanadium deposits were identified by x-ray microchemical analysis on a bare alloy substrate held in close proximity to a vanadate conversion-coated surface, and corrosion resistance of this bare surface was observed to increase during exposure. An important component of VCC formation appears to involve inorganic polymerization of V5+, which leads to the buildup of a film that passivates the surface and inhibits corrosion.

Electrochemical Charaterization of Steel Concrete under Multi-Factors Influence

2010 ◽  
Vol 177 ◽  
pp. 578-583
Author(s):  
Yu Jun Liu ◽  
Quan Jiang ◽  
Chun Zhi Zhao ◽  
Pei Yue Zhao
Keyword(s):  
Passive Film ◽  
Marine Environment ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Electrochemical Activation ◽  
Flexural Stress ◽  
Accelerated Corrosion ◽  
Result Show ◽  
Resistance Decrease ◽  
Chlorine Ion

The corrosion of steel concrete under the multi-factor of hygrothermal marine environment and flexural stress-salt spray accelerated corrosion environment was studied by potentodynamic polarization method and electrochemical impedance spectroscopy. Under the hygrothermal marine environment (Wan-ning), with the prolonging of period, passive film on the steel was depolarized, and when the period was two years, the steel started corrosion. The result show that flexural stress could accelerate chlorine ion permeation rate on the concrete, and make passive film depolarize more early. With the passive film’s depolarization, the interfacial reaction of steel/concrete develops from electrochemical activation to mass transport limitation, and the reaction resistance decrease.

Hybrid sol-gel coating incorporated with TiO2 nanosheets and anti-corrosive effects on AA2024-T3

2019 ◽  
Vol 66 (2) ◽  
pp. 215-221 ◽  
Author(s):  
Dongdong Peng ◽  
Kang Huang ◽  
Yuntao He ◽  
Zhan Zhang ◽  
Yi Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Aluminum Alloy ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Sol Gel ◽  
Corrosion Current ◽  
Corrosion Resistant ◽  
Content Type ◽  
Tio2 Nanosheets ◽  
Loading Amount

Purpose This paper aims to improve the anti-corrosive properties of aluminum alloy AA2024-T3 by coating of hybrid sol-gel coating incorporated with TiO2 nanosheets and to investigate the effect of nanosheets’ size on the improvement of corrosion-resistant performance. Design/methodology/approach A series of hybrid sol-gel films incorporated with varying amounts of TiO2 nanosheets were developed to enhance the corrosion protection performance of the bare metal. Scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to investigate the structure and morphology of the coatings obtained. In addition, the corrosion-resistant properties of the coatings were evaluated using salt spray test and electrochemical impedance spectroscopy. Findings The corrosion current was as low as 9.55 × 10-4 µA/cm2 and optimal positive corrosion potential reached −0.6 V when the size and loading amount of TiO2 nanosheet were optimized, resulting in a remarkable improvement in anti-corrosive properties. Originality/value This work first investigates the effect of incorporation of TiO2 nanoparticles on hybrid sol-gel coating on the improvement of anti-corrosive performance of aluminum alloy AA2024-T3.

scholarly journals Effect of Plasma Surface Pretreatment on Ce3+-Doped GPTMS-ZrO2 Self-Healing Coatings on Aluminum Alloy

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
N. Kumar ◽  
A. Jyothirmayi ◽  
R. Subasri
Keyword(s):  
Aluminum Alloy ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Condensation Reaction ◽  
Salt Spray ◽  
Neutral Salt ◽  
Self Healing ◽  
Surface Pretreatment ◽  
Plasma Surface ◽  
Coating Deposition

A hybrid sol synthesized from an acid-catalyzed hydrolysis and condensation reaction of 3-glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide was used as a matrix nanocomposite sol. To this sol, 0.01 M Ce3+ was added as an inhibitor to provide a self-healing coating system. The effect of an atmospheric air plasma surface pretreatment of aluminum alloy substrates prior to coating deposition of Ce3+-doped/undoped GPTMS-ZrO2 sol was studied with respect to corrosion protection. Coatings were generated by a dip coating technique employing a withdrawal speed of 5 mm/s and thermally cured at 130° C for 1 h. The coated Al surfaces were characterized using potentiodynamic polarization studies and electrochemical impedance spectroscopy. They were also subjected to accelerated corrosion testing using neutral salt spray test with 5% NaCl solution after creating an artificial scratch for more than 200 hours to assess the self-healing ability of coatings. It was observed that cerium (III) doping was effective for corrosion protection during long-term exposure to the electrolyte solution, and a plasma surface pretreatment of substrates prior to coating deposition of Ce3+-doped coatings improved the adhesion of coatings that provides enhanced corrosion protection along with self-healing ability exhibited in case of damages/scratches caused in the coating.

scholarly journals Improved anticorrosive property of waterborne epoxy coating by ultrasonic blending with small amounts of polyaniline

2021 ◽  
Author(s):  
Huan-Yan Xu ◽  
Lu Zhang ◽  
Yun-Fei Wang ◽  
Xu Han
Keyword(s):  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Salt Spray ◽  
Low Frequency ◽  
Adhesive Force ◽  
Epoxy Coating ◽  
National Standard ◽  
Electrochemical Impedance Spectra ◽  
Tafel Polarization ◽  
Waterborne Epoxy

Abstract In order to improve the anticorrosive performance of waterborne epoxy (WEP) coating, small amounts of polyaniline (PANI) were blended under ultrasonic irradiation to obtain PANI/WEP composite coatings with high dispersibility of PANI particles. The PANI/WEP composite coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). Their adhesive force level and hardness grade were tested based on the Chinese National Standard GB/T9286-1998 and GB/T6739-1996, respectively. These results indicated that, compared to the pristine WEP coating, the addition of PANI with suitable content could completely fill the micropores or microcracks and remarkably improve the hardness grade of composite coatings. The electrochemical impedance spectra (EIS) and Tafel polarization curves revealed that the addition of PANI not only could increase the impedance arc, but also could increase the impedance modulus at low frequency. Then, the salt spray tests were employed to observe the anticorrosive performance of PANI/WEP composite coatings. Finally, the enhanced anticorrosive mechanism of WEP coating by the addition of small amounts of PANI was proposed and discussed. The addition of PANI with suitable content could play an important role of physical and chemical barriers to improve the anticorrosive performance of waterborne epoxy coating.

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