scholarly journals Effect of Temperature on Corrosion Resistance of Layered Double Hydroxides Conversion Coatings on Magnesium Alloys Based on a Closed-Cycle System

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1658
Author(s):  
Xiaochen Zhang ◽  
Zhijuan Yin ◽  
Bateer Buhe ◽  
Jiajie Wang ◽  
Lin Mao ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Chemical Composition ◽  
Photoelectron Spectroscopy ◽  
Conversion Coating ◽  
Effect Of Temperature ◽  
Conversion Coatings ◽  
Closed Cycle ◽  
Cycle System ◽  
Double Hydroxide ◽  
Double Hydroxides

The effect of temperature on the corrosion resistance of layered double hydroxide (LDH) conversion coatings on AZ91D magnesium alloy, based on a closed-cycle system, was investigated. Scanning electron microscopy (SEM), photoelectron spectroscopy (XPS), and X-ray diffractometry (GAXRD) were used to study the surface morphology, chemical composition, and phase composition of the conversion coating. The corrosion resistance of the LDH conversion coating was determined through electropotentiometric polarisation curve and hydrogen evolution and immersion tests. The results showed that the conversion coating has the highest density and a more uniform, complete, and effective corrosion resistance at 50 °C. The chemical composition of the LDH conversion coating mainly comprises C, O, Mg, and Al, and the main phase is Mg6Al2(OH)16CO3·4H2O.

Preparation and characterization of a cerium conversion film on magnesium alloy

2015 ◽  
Vol 62 (4) ◽  
pp. 253-258 ◽  
Author(s):  
Jie Sun ◽  
Gang Wang
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Photoelectron Spectroscopy ◽  
Corrosion Current ◽  
Treatment Temperature ◽  
Conversion Coating ◽  
Conversion Coatings ◽  
Content Type ◽  
X Ray ◽  
Passivation Film

Purpose – The purpose of this paper was to prepare the cerium-based conversion coating on AZ91D magnesium alloy, and its compositions, micro-morphology, corrosion resistance and the chemical valence state of the film elements were investigated. Design/methodology/approach – The methodology comprised preparation of coatings at different temperatures, which then were characterized using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, an electrochemistry workstation and by means of X-ray photoelectron spectroscopy. Findings – The conversion coating had a micro-cracked morphology. The conversion coatings were composed of MgO (or Mg-OH), CeO2 and Ce2O3. The best corrosion resistance of the cerium passivation film appeared when the treatment temperature was about 35°C. Originality/value – The corrosion current densities of conversion coatings were lower by one to two orders of magnitude than the corrosion current density of the blank sample. The rare earth passivation coating prepared under the best condition could reduce the corrosion current to 3.548 × 10−6 A/cm2.

ETHANOL SENSOR OF CdO/Al2O3/CeO2 OBTAINED FROM Ce-DOPED LAYERED DOUBLE HYDROXIDES WITH HIGH RESPONSE AND SELECTIVITY

2013 ◽  
Vol 06 (03) ◽  
pp. 1350035 ◽  
Author(s):  
DONGMEI XU ◽  
MEIYU GUAN ◽  
QINGHONG XU ◽  
YING GUO ◽  
YAO WANG
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gas Sensing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Composite Oxides ◽  
Structure Morphology ◽  
Ft Ir ◽  
Ethanol Sensing ◽  
Double Hydroxide ◽  
Double Hydroxides

In this paper, Ce -doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce -doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

Properties of Conversion Coating of Magnesium Alloys by a Phosphate-Permanganate Solution

2005 ◽  
Vol 488-489 ◽  
pp. 665-668 ◽  
Author(s):  
Shu Sen Wu ◽  
Ming Zhao ◽  
Ji Rong Luo ◽  
You Wu Mao
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloys ◽  
Adhesion Force ◽  
Conversion Coating ◽  
Resistance Test ◽  
Az91d Alloy ◽  
Conversion Coatings ◽  
Good Adhesion ◽  
Better Than

A chromium-free conversion coating for AZ91D magnesium alloys has been obtained by using a phosphate-permanganate solution. Examinations have been carried out on the conversion coating for morphology, composition, adhesion force and corrosion resistance. Results show that the conversion coatings are relatively uniform and continuous, with thickness from 7µm to 10µm. They exhibit good adhesion to matrix and have some non-penetrate tiny holes on the surface. The main elements of the conversion coating of AZ91D alloy are Mg、O、P、K、Al、Mn. Results of corrosion resistance test indicate that the corrosion resistance of the conversion coating by phosphate-permanganate solution is in match to that of the conversion coating formed in a chromate solution, but for the corrosion resistance after painting, the former is better than the later.

scholarly journals Composition and Performance of Nanostructured Zirconium Titanium Conversion Coating on Aluminum-Magnesium Alloys

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sheng-xue Yu ◽  
Rui-jun Zhang ◽  
Yong-fu Tang ◽  
Yan-ling Ma ◽  
Wen-chao Du
Keyword(s):  
Corrosion Resistance ◽  
Salt Solution ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Impedance Spectrum ◽  
Conversion Coating ◽  
Mg Alloy ◽  
Electrochemical Impedance Spectrum ◽  
X Ray ◽  
Titanium Salt

Nanostructured conversion coating of Al-Mg alloy was obtained via the surface treatment with zirconium titanium salt solution at 25°C for 10 min. The zirconium titanium salt solution is composed of tannic acid 1.00 g·L−1, K2ZrF60.75 g·L−1, NaF 1.25 g·L−1, MgSO41.0 g/L, and tetra-n-butyl titanate (TBT) 0.08 g·L−1. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrum (FT-IR) were used to characterize the composition and structure of the obtained conversion coating. The morphology of the conversion coating was obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results exhibit that the zirconium titanium salt conversion coating of Al-Mg alloy contains Ti, Zr, Al, F, O, Mg, C, Na, and so on. The conversion coating with nm level thickness is smooth, uniform, and compact. Corrosion resistance of conversion coating was evaluated in the 3.5 wt.% NaCl electrolyte through polarization curves and electrochemical impedance spectrum (EIS). Self-corrosion current density on the nanostructured conversion coating of Al-Mg alloy is9.7×10-8A·cm-2, which is only 2% of that on the untreated aluminum-magnesium alloy. This result indicates that the corrosion resistance of the conversion coating is improved markedly after chemical conversion treatment.

Evaluation of the Growth Mechanism of Ti-Containing Conversion Coatings Using XPS

2015 ◽  
Vol 227 ◽  
pp. 159-162 ◽  
Author(s):  
Wlodzimierz Tylus ◽  
Juliusz Winiarski ◽  
Bogdan Szczygieł
Keyword(s):  
Chemical Composition ◽  
Deposition Time ◽  
Fold Increase ◽  
Weak Acid ◽  
Conversion Coating ◽  
Mechanical Resistance ◽  
Time Interval ◽  
Conversion Coatings ◽  
Electrogalvanized Steel ◽  
Mechanical Properties And Corrosion

Ti-containing coatings as chromate replacement were prepared on electrogalvanized steel. Zinc coatings were deposited from a weak acid chloride bath. Cr-free conversion coatings were deposited from bath composed of: TiCl3, H2SiF6, H2O2 and oxalic acid. XPS was used to evaluate chemical composition of the coatings as a function of deposition time. Deposited coating were of conversion type. Regardless of the achieved conversion coating thickness, Zn from the substrate was always present. In the coatings were identified: Zn2SiO4 / Zn4Si2O7(OH)2, ZnTiO3, ZnO, Zn (OH)2, Zn0, SiOx and Ti-O-Si in varying proportions. The chemical composition of the outer surface of the coating depended on deposition time, e.g. in a time interval 0-300 s 30 fold increase of the Si:Ti ratio and 20 fold of the Si:Zn ratio were observed. Estimated thickness of conversion coating was 3, 14, 35, and 100 nm for the time deposition of 1, 40, 80 and 300 s respectively. It is the proposed model for distinguishing Zn (0) phase from Zn (2+) quantitatively, based on the Zn L3M45M45 spectrum. The composition of the ZnTiSi conversion coating determined its mechanical properties and corrosion resistance. Standard tests carried out showed that the coatings obtained at the time of 20-40 s had the best corrosion performance and mechanical resistance

scholarly journals Corrosion Resistance of Electrochemically Synthesized Modified Zaccagnaite LDH-Type Films on Steel Substrates

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7389
Author(s):  
Michael Kahl ◽  
Teresa D. Golden
Keyword(s):  
Corrosion Resistance ◽  
Layered Double Hydroxide ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
X Ray Diffraction ◽  
X Ray ◽  
Double Hydroxide ◽  
Double Hydroxides ◽  
Steel Substrates ◽  
Deposited Films

Modified zaccagnaite layered double hydroxide (LDH) type films were synthesized on steel substrates by pulsed electrochemical deposition from aqueous solutions. The resulting films were characterized by X-ray diffraction, scanning electron microscopy/X-ray dispersive spectroscopy, and Fourier transform infrared spectroscopy. Structural characterization indicated a pure layered double hydroxide phase; however, elemental analysis revealed that the surface of the films contained Zn:Al ratios outside the typical ranges of layered double hydroxides. Layer thickness for the deposited films ranged from approximately 0.4 to 3.0 μm. The corrosion resistance of the film was determined using potentiodynamic polarization experiments in 3.5 wt.% NaCl solution. The corrosion current density for the coatings was reduced by 82% and the corrosion potential was shifted 126 mV more positive when 5 layers of modified LDH coatings were deposited onto the steel substrates. A mechanism was proposed for the corroding reactions at the coating.

Study on Technological Process of Cerium-Based Conversion Coating on Aluminum

2009 ◽  
Vol 79-82 ◽  
pp. 879-882
Author(s):  
Ji Hui Xu ◽  
Xin Wang ◽  
Jing Wang ◽  
Qiu Ju Zheng
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Corrosion Resistance ◽  
Technological Process ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Measurement ◽  
Conversion Coating ◽  
X Ray ◽  
Scanning Electron ◽  
Industrial Aluminum

The Cerium-based conversion coating is formed on the industrial aluminum(1060) by using chemical immersion. The microstructures of the conversion coating have been examined by scanning electron microscopy(SEM). The electrochemical measurement result shows that the corrosion resistance of aluminum is significantly improved after the conversion coating was formed. The result of X-ray photoelectron spectroscopy (XPS) shows that the cerium conversion coating mainly consisted of oxide of aluminum, CeO2 and TiO2. The formation mechanism of the Cerium-based conversion coating is investigated.

EIS Study of Molybdate Conversion Coatings Formed on AZ91D Magnesium Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 279-285
Author(s):  
Li Ping Wu ◽  
Zhong Dong Yang
Keyword(s):  
Corrosion Resistance ◽  
Charge Transfer ◽  
Magnesium Alloy ◽  
Charge Transfer Resistance ◽  
Conversion Coating ◽  
Conversion Coatings ◽  
Bath Composition ◽  
Optimum Conditions ◽  
Transfer Resistance ◽  
Az91d Magnesium Alloy

An environmentally friendly molybdate conversion coating based surface treatment was developed for AZ91D magnesium alloy. The EIS technique was employed to study the effects of the conversion bath composition and temperature on the corrosion protection performance of molybdate conversion coatings on AZ91D magnesium alloys. The optimum conditions under which obtained conversion coatings showed the best corrosion resistance were determined. The Nyquist results showed that the value of charge transfer resistance increased by 22.5 times for the sample treated in the optimized molybdate conversion bath.

Zirconate Conversion Coatings on Al Alloy by Electrochemical Method

2012 ◽  
Vol 460 ◽  
pp. 86-89
Author(s):  
Qi Zhou ◽  
Hong Yan Liu ◽  
Xiu Lian Cheng ◽  
Guang Sen Zhang
Keyword(s):  
Corrosion Resistance ◽  
Paint Film ◽  
Chemical Conversion ◽  
First Grade ◽  
Conversion Coating ◽  
Complexing Agents ◽  
Complexing Agent ◽  
Al Alloy ◽  
Conversion Coatings ◽  
Electrochemical Conversion

Chromium-free conversion coatings were generated to replace chromate chemical process by electrolysis treatment LY12 aluminum alloy in zirconate solution. Film thickness, dropping test, the adhesion between aluminum and paint film were tested for single-factor experiments and orthogonal to seek better electrolysis process. The paint adhesion is the first grade for electrochemical conversion solution containing complexing agents, or it is the second grade without complexing agents. When DNS complexing agent is 2 ~ 5g/L, film corrosion resistance rises with the increasing content of complexing agent. If voltage is too low, corrosion resistance of conversion coating is poor; voltage is too high, the films form powders. Better formulations for zirconate conversion coating are: 5g/L DNS complexing agent, 10V voltage, treatment temperature is 40°C. Electrochemical conversion coating is thinner than chemical conversion, but the corrosion resistance is better because the electrochemical conversion coatings are smoother and compacter than the chemical conversion coating. The paint films on electrochemical conversion coating are smoother than the chemical one. Two kinds of conversion coatings have very good adhesion with paint film up to the first level. Electrochemical conversion coatings thickness is 2.5 μm, bubble time of NaOH-glycerine solution on them is up to 92s.

scholarly journals Synthesis, Characterization and Photocatalytic Performance of Calcined ZnCr-Layered Double Hydroxides

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3051
Author(s):  
Somia Djelloul Bencherif ◽  
Juan Jesús Gallardo ◽  
Iván Carrillo-Berdugo ◽  
Abdellah Bahmani ◽  
Javier Navas
Keyword(s):  
Photocatalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Textural Properties ◽  
Operational Parameters ◽  
X Ray ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Crystal Violet Dye ◽  
Double Hydroxide ◽  
Double Hydroxides

The development of new materials for performing photocatalytic processes to remove contaminants is an interesting and important research line due to the ever-increasing number of contaminants on our planet. In this sense, we developed a layered double hydroxide material based on Zn and Cr, which was transformed into the corresponding oxide by heat treatment at 500 °C. Both materials were widely characterized for their elemental composition, and structural, morphological, optical and textural properties using several experimental techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy and physisorption techniques. In addition, the photocatalytic activity of both materials was analysed. The calcined one showed interesting photocatalytic activity in photodegradation tests using crystal violet dye. The operational parameters for the photocatalytic process using the calcined material were optimised, considering the pH, the initial concentration of the dye, the catalyst load, and the regeneration of the catalyst. The catalyst showed good photocatalytic activity, reaching a degradation of 100% in the optimised conditions and showing good performance after five photodegradation cycles.

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