Corrosion resistance of zinc electrodeposited from acidic and alkaline electrolytes using pulse current

2009 ◽  
Vol 63 (5) ◽  
Author(s):  
Matilda Zemanová
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Test ◽  
Pulse Current ◽  
Zinc Coating ◽  
Accelerated Corrosion ◽  
X Ray ◽  
Before And After ◽  
Alkaline Electrolytes ◽  
Zinc Coatings ◽  
Chrome Iii

AbstractCorrosion resistance of zinc coatings was investigated in an accelerated corrosion test in a condensation chamber. Zinc was electrodeposited from alkaline and acidic electrolytes using direct current (DC) or pulse current (PC). The zinc coating was subsequently protected against corrosion with a chrome (III) layer. Morphology and structure of the coatings was investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) before and after the corrosion test. Corrosion resistance of alkaline zinc coatings electrodeposited with DC and PC under test conditions was found to be comparable. The corrosion resistance of zinc coatings deposited from acidic electrolytes by PC was lower in comparison with corrosion resistance of zinc coatings deposited using DC.

scholarly journals CHARACTERISTIC OF XONOTLITE SYNTHESIZED BY HYDROTHERMAL REACTION USING RICE HUSK ASH AND ITS APPLICATION TO ABSORB CHROME (III) SOLUTION

2021 ◽  
Vol 55 (6) ◽  
Author(s):  
Trung Kien Pham ◽  
Tran Ngo Quan
Keyword(s):  
Rice Husk ◽  
Rice Husk Ash ◽  
Hydrothermal Reaction ◽  
Mekong Delta ◽  
Molar Ratio ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Xrf Scanning ◽  
Before And After ◽  
Chrome Iii

In this paper, we report on synthesizing xonotlite, calcium silicate hydrate (CSH), via a hydrothermal reaction using rice husk from the Mekong Delta, Vietnam. The rice husks were burnt at 1000 °C for 3 h. Grey rice husk ash was collected, then mixed with Ca(OH)2 at a Ca/Si molar ratio of 1 : 1. This was followed by a hydrothermal reaction at 180 °C for 24 h and 48 h to obtain the xonotlite mineral. Before and after adsorption, 3-mm xonotlite pellets were thoroughly characterized using X-ray diffractometry (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and ultraviolet-visible (UV-VIS) spectroscopy. This material has potential application in chromium(III) removal during a chrome-plating process. The adsorption efficiency of the 3-mm pellet samples reached more than 76 % after 12 h.

Corrosion Resistance by Sodium Metavanadate for AZ91D Magnesium Alloy

2014 ◽  
Vol 575 ◽  
pp. 170-174 ◽  
Author(s):  
Toha Nor Fadzilah ◽  
S. Norbahiyah ◽  
Mohd Zain Mohamad Zamzuri
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Oxide Film ◽  
Corrosion Test ◽  
Energy Dispersive Spectrometry ◽  
Optical Microscope ◽  
X Ray ◽  
Sodium Metavanadate ◽  
Az91d Magnesium Alloy ◽  
Polarization Technique

An oxide film was prepared on AZ91D magnesium alloy by anodizing in solution containing sodium metavanadate (NaVO3). The corrosion resistance of the substrate was investigated at a fixed current density 10 mA/cm2for 5 mins with different concentration of solution in the range of 0 – 1.0 g/l. The surface morphology, phase structure and corrosion resistance of oxide film were studied by optical microscope, scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) and X-ray diffractometer (XRD), potentiodynamic polarization technique and corrosion test.

Study of the Temperature Effect on the Structure and Thickness of Hot-Dip Zinc Coatings on Fixing Products

2014 ◽  
Vol 698 ◽  
pp. 355-359 ◽  
Author(s):  
Olga Bondareva
Keyword(s):  
Coating Thickness ◽  
Elevated Temperatures ◽  
Zinc Coating ◽  
High Strength ◽  
Bath Temperature ◽  
X Ray ◽  
Minimal Thickness ◽  
Galvanized Coating ◽  
Zinc Coatings ◽  
Scanning Electron

Hot-dip galvanizing of steels is usually performed by immersing the metal in a bath with molten zinc in the temperature range from 450 to 460 °C. In some cases it is necessary to obtain a minimal coating thickness. For example, high-strength bolts and other fixing products require a minimal thickness of the coating because a too thick zinc coating requires additional work on re-threading, which leads to spalling of coatings, a loss of corrosion resistance and, consequently, failure of the entire product. The main aim of this work was to study the influence of elevated temperatures of hot-dip galvanizing on the thickness and microstructure of zinc coatings on bolts and nut preform. The microstructure and elemental composition of the coating were studied by scanning electron microscopy and energy dispersion X-ray microanalysis. It was found that the coating thickness obtained in the range between 475 and 535°C decreases with temperature and reaches a minimum at 535°C. The structure of the coating after high-temperature hot-dip galvanizing was fundamentally different from the structure of the coating made at standard temperatures 450-460°C. This coating formed at 535°C was dense, homogeneous, non-porous and composed of a mixture of the δ and ζ-phases without distinct phase boundaries. That’s why it was recommended to maintain the bath temperature in the range between 533°C and 537°C. It allows us to obtain a hot-dip galvanized coating of a minimal thickness and a good quality on fixing products.

Study of Microstructure and Corrosion Resistance of Zinc Electrodeposits before and after Black Chromating

2017 ◽  
Vol 751 ◽  
pp. 119-124
Author(s):  
Kanokwan Saengkiettiyut ◽  
Pranee Rattanawaleedirojn ◽  
Adisak Thueploy ◽  
Jumpot Wanichsampan ◽  
Yuttanant Boonyongmaneerat
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Alkaline Electrolyte ◽  
Corrosion Properties ◽  
Electrochemical Testing ◽  
Before And After ◽  
Coat Layer ◽  
Zinc Coatings ◽  
Salt Spray Testing

In this work, microstructure and corrosion properties of zinc electroplated steel before and after black chromating was investigated. The test samples were prepared by electrodeposition process, using a commercially-available alkaline electrolyte. Subsequently, the galvanized samples were applied with a black chromate-based passivation layer and a clear top-coat layer. Their microstructures were examined using X-ray diffractometry and scanning electron microscopy. The corrosion resistance of the samples was assessed with the salt spray test, following the ASTM B117, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization in 5 wt.% NaCl solutions. The study showed that zinc electroplated steels exhibit (110) crystallographic orientation. The passivation and top-coat layers did not affect the microstructure of the zinc layer, and covered uniformly on the zinc layer for all sets of samples. The corrosion resistant results obtained from salt spray testing and electrochemical testing revealed that the microstructure of zinc coatings prepared by using different applied current did not influence on their corrosion resistance markedly. While black passivation followed by top coating provided a significant improvement on corrosion resistance of the coatings.

Characterization of Ni-P and Ni-P-Al2O3 Heat Treated Layers

2017 ◽  
Vol 1143 ◽  
pp. 26-31
Author(s):  
Lucica Balint ◽  
Gina Genoveva Istrate
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Composite Coatings ◽  
Treatment Temperature ◽  
Initial State ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated ◽  
Before And After

Research has shown the relationship among hardness, usage and corrosion resistance Ni-P-Al2O3 composite coatings on steel support heat treated. The electroless strips were heat treated at 200°C, 300°C, 400°C, 500°C and 600°C. Further studies on corrosion, hardness and usage revealed changes in properties, compared to the initial state, both on the strips coated with Ni-P and the ones coated with Ni-P-Al2O3 composite. The samples have been studied before and after the heat treatment via Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Analysis (EDX) and X-Ray Diffraction (XRD). The results show that untreated Ni-P layers exhibit strong corrosion resistance, while hardness and usage increase with heat treatment temperature, with a peak at 400 °C. Using suspended particles co-deposition, led to new types of layers, some with excellent hardness and usage properties. Corrosion resistance increase with heat treatment. Coating layers can be adjusted to the desired characteristics, by selecting proper parameters for the expected specific results.

Alloying Element Nickel Influence on Microstructure and Properties of Weathering Steels

2011 ◽  
Vol 295-297 ◽  
pp. 1436-1440 ◽  
Author(s):  
Zhi Yong Liu ◽  
Xin Lai He ◽  
Ji Qing Chen ◽  
Shan Wu Yang ◽  
Bang Wen Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Corrosion Test ◽  
Nickel Content ◽  
Alloying Element ◽  
Accelerated Corrosion ◽  
Corrosion Resistant ◽  
Microstructure And Properties ◽  
Microstructure Observation ◽  
Accelerated Corrosion Test

By testing the mechanical properties, microstructure observation, accelerated corrosion test, the effect of alloying element nickel on microstructure and properties of weathering steels was studied. The results showed that nickel content from 0 to 0.44%（mass percent）have little influence on microstructure and mechanical properties of weathering steels.The corrosion resistance enhanced with increasing nickel content, and nickel content of 0.11% or more had significant enfluence on corrosion resistant performance of weathering steels.

Preparation and Salt Spray Corrosion Resistance of Ni/BN and NiCrAl/BN Coatings

2013 ◽  
Vol 537 ◽  
pp. 67-70
Author(s):  
Feng Zhang ◽  
Chuan Bing Huang ◽  
Wei Liu ◽  
Kui Zhou ◽  
Wen Ting Zhang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Test ◽  
Open Circuit Potential ◽  
Salt Spray ◽  
Open Circuit ◽  
X Ray Diffraction ◽  
Salt Spray Corrosion ◽  
X Ray ◽  
Corrosion Behaviors ◽  
Scanning Electron

Ni/BN and NiCrAl/BN abradable sealing coatings used in turbo engines were prepared by plasma spray technology. The phases and the microstructures of the coatings were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Corrosion behaviors of these coatings were investigated with open-circuit potential (OCP) and salt spray corrosion test. The results showed that the NiCrAl/BN possess better corrosion resistance as compared with Ni/BN.

Effect of Homogenization Treatment on Microstructure and Properties of ZnAl15 Alloy

2014 ◽  
Vol 875-877 ◽  
pp. 1250-1254 ◽  
Author(s):  
Xin Qi Yan ◽  
Yong Chen ◽  
Sheng Xin Liu ◽  
Wei Min Long ◽  
Jun Lan Huang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Test ◽  
Room Temperature ◽  
Discontinuous Precipitation ◽  
Accelerated Corrosion ◽  
Homogenization Treatment ◽  
Lamellar Structures ◽  
Α Phase ◽  
Supersaturated Solid Solutions ◽  
Accelerated Corrosion Test

The microstructure, microhardness and corrosion resistance of as-cast and as-annealed ZnAl15 alloys were investigated by OM, SEM, EDX and DSC techniques. It was found that microstructure of as-cast ZnAl15 alloy was primary dendrites and eutectic matrix. But Primary discontinuous precipitation of αs and βs phase occurred at room temperature. During homogenization treatment, discontinuous precipitation of αs and βs phase occurred completely and accompanied with emitting heat. The final microstructures of decomposed αs and βs phase in primary dendrites were fine and coarse lamellar structures respectively. The final microstructures of decomposed βs, which located at the edges of the αs phases or in eutectic matrix were that α phase distributed in η matrix. The microhardness of both primary dendrites and eutectic matrix in ZnAl15 alloys decreased after homogenization treatment due to the decomposition of supersaturated solid solutions. The result of accelerated corrosion test showed that homogenization treatment has a certain beneficial effect on the corrosion resistance of ZnAl15 alloy.

Preliminary Study of DLC Coatings Aiming to the Corrosion Protection of Ferrous Materials

2010 ◽  
Vol 10 ◽  
pp. 113-120
Author(s):  
G. Vourlias ◽  
N. Pistofidis ◽  
D. Chaliampalias ◽  
Panos Patsalas ◽  
Efstathios K. Polychroniadis
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Protection ◽  
Zinc Coating ◽  
Chemical Vapor ◽  
Harsh Environments ◽  
Dlc Coatings ◽  
Preliminary Study ◽  
Diffraction Patterns ◽  
Zinc Coatings ◽  
Galvanized Coatings

Zinc hot-dip galvanizing is one of the most effective methods for the corrosion protection of ferrous substrates. However, the failure of zinc coatings is possible when exposed to harsh environments for rather long periods. The application of a thin diamond like carbon (DLC) film on the top of the zinc coating might be a promising method for promoting their corrosion resistance. In the present work, a DLC thin film was deposited on zinc galvanized coatings by Plasma Enhanced Chemical Vapor Deposition. The as-formed film was composed of nanostructured and amorphous areas. The electron diffraction patterns acquired from the nanograins correspond to carbon phases with d-spacing ranging from diamond to graphite. Additionally, after 18 days of exposure in a simulated marine atmosphere, the DLC coated samples were proven to be more resistant than the naked galvanized coatings indicating its potential to improve the corrosion resistance of galvanized ferrous materials.

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