CORROSION PROTECTION OF AZ91D Mg ALLOY COATING WITH MICRO-ARC OXIDATION FILM EVALUATED BY IMMERSION AND ELECTROCHEMICAL TESTS

2005 ◽  
Vol 12 (02) ◽  
pp. 279-287 ◽  
Author(s):  
X. P. ZHANG ◽  
G. CHEN
Keyword(s):  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Alloy Coating ◽  
Charge Transfer Resistance ◽  
Mg Alloy ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Electrochemical Tests ◽  
Micro Arc Oxidation ◽  
Eis Measurements

This paper describes the preliminary results of corrosion protection of AZ91D Mg alloy coated with a micro-arc oxidation (MAO) coating. The corrosion behavior of coated substrates was evaluated by means of immersion and electrochemical tests in 5 wt.% NaCl solution. The immersions tests include weight loss measurement after full or partial immersion with the whole coat and full immersion with the damaged coat. The electrochemical tests include polarization curves and electrochemical impedance spectroscopy (EIS) measurements. The results of immersion and electrochemical tests show that micro-arc oxidation (MAO) surface treatment can significantly improve the corrosion resistance of the AZ91D Mg alloy in 5% NaCl solution, and the corrosion protection effect of the MAO coating is not sensitive to pores or cracks in the coating. The charge transfer resistance R ct , increases from about 1.669Ωcm2 for the uncoated alloy to about 1113Ωcm2 after being coated with MAO coat.

IMMERSION AND ELECTROCHEMICAL TESTS STUDY ON CORROSION RESISTANCE OF CHROME-FREE CHEMICAL CONVERSION FILM ON AZ91D Mg ALLOY IN 5 wt% NaCl SOLUTION

2005 ◽  
Vol 12 (03) ◽  
pp. 417-424
Author(s):  
X. P. ZHANG ◽  
G. CHEN
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Chemical Conversion ◽  
Alloy Coating ◽  
Charge Transfer Resistance ◽  
Mg Alloy ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Electrochemical Tests

Immersion and electrochemical tests have been applied to study corrosion protection of AZ91D Mg alloy coating with chrome-free chemical conversion (CCC) coat in 5wt% NaCl solution. The immersions tests include weight-loss measurements after full or partial immersion with whole coating and full immersion with damaged coating. The electrochemical tests include electrochemical impedance spectroscopy (EIS) and polarization curves measurement. The results of immersion and electrochemical tests show that chrome-free chemical conversion (CCC) surface treatment can significantly improve the corrosion resistance of AZ91D Mg alloy in 5% NaCl solution, and that the corrosion protection effect of CCC coating is not sensitive to pores or cracks. The equivalent circuit models are fitted from Nyquist plots for the uncoated specimens and the CCC-coated specimens. The charge transfer resistance, R ct , increases from about 1.669 Ω cm2 for the uncoated alloy to about 210 Ω cm2 after the alloy is coated with CCC coating.

scholarly journals Electrochemical Corrosion Behavior of Ni-Fe-Co-P Alloy Coating Containing Nano-CeO2 Particles in NaCl Solution

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2614 ◽  
Author(s):  
Xiuqing Fu ◽  
Wenke Ma ◽  
Shuanglu Duan ◽  
Qingqing Wang ◽  
Jinran Lin
Keyword(s):  
Composite Coating ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Electrochemical Corrosion ◽  
Alloy Coating ◽  
Charge Transfer Resistance ◽  
Corrosion Mechanism ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Electrochemical Corrosion Behavior

In order to study the effect of nano-CeO2 particles doping on the electrochemical corrosion behavior of pure Ni-Fe-Co-P alloy coating, Ni-Fe-Co-P-CeO2 composite coating is prepared on the surface of 45 steel by scanning electrodeposition. The morphology, composition, and phase structure of the composite coating are analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The corrosion behavior of the coatings with different concentrations of nano-CeO2 particles in 50 g/L NaCl solution is studied by Tafel polarization curve and electrochemical impedance spectroscopy. The corrosion mechanism is discussed. The experimental results show that the obtained Ni-Fe-Co-P-CeO2 composite coating is amorphous, and the addition of nano-CeO2 particles increases the mass fraction of P. With the increase of the concentration of nano-CeO2 particles in the plating solution, the surface flatness of the coating increases. The surface of Ni-Fe-Co-P-1 g/L CeO2 composite coating is uniform and dense, and its self-corrosion potential is the most positive; the corrosion current and corrosion rate are the smallest, and the charge transfer resistance is the largest, showing the best corrosion resistance.

Corrosive wear and electrochemical corrosion behaviors of laser thermal sprayed CoCrAlYTaSi coatings in 3.5 Wt.% NaCl solution

2019 ◽  
Vol 66 (5) ◽  
pp. 537-543 ◽  
Author(s):  
Zhou Weitong ◽  
Kong Dejun
Keyword(s):  
Abrasive Wear ◽  
Chemical Elements ◽  
Electrochemical Corrosion ◽  
Alloy Coating ◽  
Corrosive Wear ◽  
Charge Transfer Resistance ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Content Type ◽  
Wear Rates

Purpose This paper aims to enhance the corrosive wear and electrochemical corrosion of Ti–6Al–4V alloy. Design/methodology/approach A CoCrAlYTaSi alloy coating was fabricated on Ti–6Al–4V alloy using a laser thermal spraying (LTS). The surface and cross-section morphologies, chemical elements, phases and bonding strength of the obtained coating were analyzed using a scanning electron microscope, energy dispersive spectroscope, X-ray diffraction and scratch test, respectively, The corrosive wear and electrochemical corrosion of CoCrAlYTaSi coating in 3.5 Wt.% NaCl solution were investigated using a wear tester and electrochemical workstation, respectively. Findings The average coefficient of frictions (COFs) of CoCrAlYTaSi coating under the wear loads of 2, 4 and 6 N are 1.31, 1.02 and 0.88, respectively; and the corresponding wear rates are 0.66 × 10−4, 1.10 × 10−4 and 1.30 × 10−4 mm3·N–1·m–1, respectively. The wear mechanism under the wear load of 2 N is abrasive wear, while those under the wear loads of 4 and 6 N are adhesive wear and abrasive wear. The charge transfer resistance of CoCrAlYTaSi coating is 5.368 × 105 Ω·cm2, higher than 2.193 × 105 of the substrate. Originality/value In this study, a CoCrAlYTaSi coating was firstly fabricated on Ti–6Al–4V alloy using a LTS. Its corrosive wear and electrochemical corrosion in 3.5 Wt.% NaCl solution were investigated, which played a protective role of corrosive wear on Ti–6Al–4V alloy.

scholarly journals The Effect of Achyranthes aspera Extracts on Mild Steel Corrosion in Industrial Water Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Chikkur B. Pradeep Kumar ◽  
Kikkeri N. Mohana
Keyword(s):  
Mild Steel ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Steel Corrosion ◽  
Charge Transfer Resistance ◽  
Water Medium ◽  
Industrial Water ◽  
Transfer Resistance ◽  
Achyranthes Aspera ◽  
Eis Measurements

Achyranthes aspera (AA) extracts were studied as corrosion inhibitor for mild steel (MS) in industrial water medium using mass loss and electrochemical techniques. The results of the study revealed that AA extracts inhibit MS corrosion through adsorption process following Langmuir adsorption isotherm model. The protection efficiency increased with increase in inhibitor concentration and decreased with temperature. The electrochemical impedance spectroscopy (EIS) measurements showed that the charge transfer resistance increases with increase in the concentration of AA extracts. The polarization curves obtained indicate that AA extracts act as mixed type of inhibitor. Scanning electron microscopy (SEM) was used to analyze the surface adsorbed film.

Microstructure and Electrode Characteristics of Ti-V-Cu-Cr-Ni Metal Hydride Electrode Alloy

2012 ◽  
Vol 512-515 ◽  
pp. 1933-1936
Author(s):  
Yu Qing Qiao ◽  
Min Shou Zhao ◽  
Li Min Wang
Keyword(s):  
Metal Hydride ◽  
Electrochemical Impedance ◽  
Secondary Phase ◽  
Charge Transfer Resistance ◽  
Solid Solution Phase ◽  
Transfer Resistance ◽  
Metal Hydride Electrode ◽  
Eis Measurements ◽  
Increasing Temperature ◽  
Electrode Characteristics

Microstructure and electrode characteristics of Ti-V-Cu-Cr-Ni metal hydride electrode alloy have been investigated by XRD, FESEM-EDS and EIS measurements. The result shows that the alloy is mainly composed of V-based solid solution phase with body-centered-cubic structure and TiNi-based secondary phase. The discharge capacity increases with increasing temperature in a wider temperature region from 303 K to 343 K. The result of electrochemical impedance spectrometry indicates that the charge transfer resistance decreases with increasing temperature, while the exchange current density in the bulk of the alloy increase with increasing temperature.

Evaluation of corrosion inhibition and adsorption behavior of Thymuszygis subsp. gracilis volatile compounds on mild steel surface in 1 m HCl

2020 ◽  
Vol 38 (2) ◽  
pp. 137-149
Author(s):  
Mohamed Ouknin ◽  
Abderrahmane Romane ◽  
Jean-Pierre Ponthiaux ◽  
Jean Costa ◽  
Lhou Majidi
Keyword(s):  
Mild Steel ◽  
Electrochemical Impedance ◽  
Aggressive Medium ◽  
Three Dimensional ◽  
Steel Corrosion ◽  
Charge Transfer Resistance ◽  
Infrared Analysis ◽  
Transfer Resistance ◽  
3D Profilometry ◽  
Eis Measurements

AbstractThe inhibition effect of Thymus zygis subsp. gracilis (TZ) on mild steel corrosion in 1 m hydrochloric acid has been investigated by weight loss measurements, surface analysis [scanning electron microscopy (SEM)-energy-dispersive X-ray (EDX), three-dimensional (3D) profilometry, and Fourier transform infrared analysis], potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Gravimetric results indicate that TZ exhibits good inhibition efficiency of 80.40% attained at 3 g/l. Polarization measurements show that the studied inhibitor is a mixed type. EIS measurements revealed that the charge transfer resistance increases with increasing concentration of TZ, which suggests a Langmuir adsorption isotherm model. Based on SEM-EDX and 3D profilometry, it appears that the surface is remarkably improved in the presence of TZ oil compared to that exposed to the acid medium without TZ oil. From the obtained results, it can be concluded that this oil is a new natural substance that can be used against material corrosion in aggressive medium.

scholarly journals Synthesis of MoIn2S4@CNTs Composite Counter Electrode for Dye-Sensitized Solar Cells

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Gentian Yue ◽  
Renzhi Cheng ◽  
Xueman Gao ◽  
Leqing Fan ◽  
Yangfan Mao ◽  
...  
Keyword(s):  
Counter Electrode ◽  
Electrochemical Impedance ◽  
Dye Sensitized Solar Cells ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Electrochemical Tests ◽  
One Step ◽  
Low Charge ◽  
Adsorption Desorption ◽  
Sensitized Solar Cells

Abstract A ternary and composite MoIn2S4@CNTs counter electrode (CE) with a hedgehog ball structure was synthesized by using a facile one-step hydrothermal method. The composite MoIn2S4@CNTs film possesses large specific surface area through N2 adsorption-desorption isotherms test, which is advantageous to adsorb more electrolyte and provide larger active contact area for the electrode. In addition, the composite MoIn2S4@CNTs CE exhibits low charge transfer resistance and fine electrocatalytic ability made from a series of electrochemical tests including cyclic voltammetry, electrochemical impedance, and Tafel curves. Under optimal conditions, the DSSC based on the MoIn2S4@CNTs-2 composite CE achieves an impressive power conversion efficiency as high as 8.38%, which remarkably exceeds that of the DSSCs with the MoIn2S4 CE (7.44%) and the Pt electrode (8.01%). The current work provides a simplified preparation process for the DSSCs.

Corrosion Analysis of Reinforcing Steels in Mortar for Nuclear Facilities

2009 ◽  
Author(s):  
Toshiyasu Nishimura
Keyword(s):  
Electrochemical Impedance ◽  
Initial Period ◽  
Charge Transfer Resistance ◽  
Ion Concentration ◽  
Reinforcing Steel ◽  
Nuclear Facilities ◽  
Good Correspondence ◽  
Transfer Resistance ◽  
Eis Measurements ◽  
Cover Thickness

It is important to estimate the corrosion of reinforcing steel in mortar facilities, because the nuclear plants are located near the sea side. In the case of environmental factors in mortar, the Cl ion concentration and pH were monitored by inserting microelectrodes into artificial pores in the mortar. At the same time, the corrosion behavior of the reinforcing steel was investigated by EIS (electrochemical impedance spectroscopy). In the EIS measurements of the reinforcing steel, diffusion behavior was confirmed in the initial period, but diffusion could no longer be observed after 35 day. In comparison with a 10mm cover thickness, a 20mm cover thickness showed a higher impedance behavior. The Cl ion concentration in the mortar was obtained using Ag/AgCl microelectrodes, showing that this behavior is generally controlled by diffusion. When the diffusion equation was used in this work, the diffusion coefficient (Dc) showed a high value of Dc = 2×10−4 mm2/sec. Similarly, the pH in the mortar was obtained using W/WOx microelectrodes. With a 20mm cover thickness, pH was limited to approximately pH11, but with a 10mm cover thickness, pH continued to decrease to around pH9.5. The latter phenomenon was considered to be the result of neutralization by penetration of the immersion solution from the surface. Based on the results of monitoring with the microelectrodes, solutions simulating those in the pores in mortar were prepared and used in EIS measurements. The charge transfer resistance Rct in the simulated solutions showed good correspondence with the impedance in the low frequency region (2mHz) in the actual mortar. This is attributed to the fact that the corrosion of reinforcing steel was controlled by the solution conditions (mainly Cl concentration and pH) in the pores in mortar. If these solution conditions (Cl concentration, pH) exceed threshold values, it was found that the passivation film is destroyed, resulting in high corrosion.

scholarly journals Corrosion Behavior of Alloyed Cast Iron in Ethylene Glycol-Based Engine Coolants at Elevated Temperature

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 357
Author(s):  
Gaurav Argade ◽  
Anusha Chilukuri ◽  
Justin Perry ◽  
Monica Viers ◽  
Jacob Steenhoek ◽  
...  
Keyword(s):  
Cast Iron ◽  
Elevated Temperature ◽  
Electrochemical Impedance ◽  
Engine Performance ◽  
Sharp Decrease ◽  
Charge Transfer Resistance ◽  
Organic Additives ◽  
Transfer Resistance ◽  
Electrochemical Tests ◽  
Engine Coolant

For enhanced engine performance, corrosivity of the engine coolants would play a significant role. In this work, corrosion investigation was performed on cast iron material in pre-mixed engine coolant environment to understand the threshold limits of contaminants. The pre-mixed coolant contained combination of organic additives viz. sebacate (SA), 2-ethylhexonate (2-EH), and tolyltriazole (TTA) with varying concentrations of chloride contaminant. Constant immersion of cast iron samples in engine coolant with different chloride levels at 90 °C was followed by room temperature electrochemical tests. The potentiodynamic polarization tests showed no instability until 100 ppm chloride additions exposed up to 28 days. At lower frequencies in electrochemical impedance spectroscopy (EIS) spectra, inhibition layer characteristics changed from highly capacitive to highly resistive and concurrently a sharp decrease in charge transfer resistance was observed with time for samples exposed to >100 ppm chloride levels. In the longer duration corrosion tests, higher pit depths with increased number density of attacks were observed for cast iron samples exposed to engine coolants containing >100 ppm chloride. For elevated temperature exposures a threshold limit of <200 ppm chloride was established for cast iron samples.

Effect of Cl- Content, pH Value and CO2 on Electrochemical Corrosion Features of Cr15 Super Martensitic Stainless Steel

2013 ◽  
Vol 738 ◽  
pp. 92-96
Author(s):  
Jin Ming Long ◽  
Quan Bin Liu ◽  
Kun Yu Zhao ◽  
Qi Long Yong ◽  
Jie Su
Keyword(s):  
Stainless Steel ◽  
Martensitic Stainless Steel ◽  
Electrochemical Impedance ◽  
Ph Value ◽  
Charge Transfer Resistance ◽  
Uniform Corrosion ◽  
Nacl Solution ◽  
Transfer Resistance ◽  
Pitting Potential ◽  
Super Martensitic Stainless Steel

The corrosion behavior of a Cr15 super martensitic stainless steel (Cr15 SMSS) was investigated in NaCl solutions by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Effects of Cl-content, pH value and saturated CO2on corrosion were sdudied. It was found that the parameters of maintaining passivity current density (ip), the critical pitting potential (Eb) and charge transfer resistance (Rt) of Cr15 SMSS varied widely under different conditions. The corrosion resistance of Cr15 SMSS decrease with increasing Cl-concentration and lowering pH value. BothipandEbincrease for Cr15 SMSS in CO2-saturated NaCl solution, which verified that the CO2in NaCl solution can result in lower pitting sensitivity and higher uniform corrosion rate to Cr15 SMSS.

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