scholarly journals An Experimental Study of Sintered (Ni-Cr-xAl2O3) Composites

10.30544/210 ◽  
2016 ◽  
Vol 22 (3) ◽  
pp. 165-178
Author(s):  
Alaa Abdulhasan Atiyah
Keyword(s):  
Protective Layer ◽  
Softening Temperature ◽  
Corrosion Current ◽  
Open Circuit ◽  
Corrosion Properties ◽  
Positive Direction ◽  
The Matrix ◽  
Base Composite ◽  
Alumina Composite ◽  
Metallic Composites

This paper deals with the (Ni-Cr- xAl2O3) metallic composites (MCCs). Restraining of of thermal expansion at adequate mechanical and corrosion properties is the main objective of this work. Composites are fabricated with four weight percentages of (x = 1, 2, 5 and 10% Al2O3). Compacting and sintering has accomplished at (636 MPa) and 1250oC for 7 hrs. All sintered compacts were examined for phases and microstructure featuring. Results have indicated, the incorporation of Al2O3 with the matrix is due to the efficient sintering conditions, that diminishing the grain growth and increasing the softening temperature from 850°C to become 1350°C. Volume expansion appeared in the base sintered composites (NiCr-xAl2O3) due to pores evolution according to SEM observation. As, the Al2O3 has increased, the microhardness and corrosion resistance have improved. DSC results show a clear one exothermic and one endothermic reaction were occurred during the heating cycle. Corrosion behavior of fabricated composites was estimated by polarization curves using Potentiostat at scan rate 3 mV.sec-1. Potential-time measurements showed the formation of protective layer on surface composites compared with Ni-Cr base composite through an obtaining of the nobler open circuit potentials for composites. Corrosion parameters were estimated by the Tafel extrapolation method, these parameters indicated that the corrosion potential shifted toward a positive direction in addition to get lower corrosion current density especially for Ni-Cr/5%Alumina composite.

Structural Characterization and Corrosion Properties of BTESPT Silane Films on Surface of 2024-T6 Aluminium Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 1111-1116 ◽  
Author(s):  
Ming An Chen ◽  
Xuan Xie ◽  
Guo Fu Xu ◽  
Hui Zhong Li ◽  
Xin Ming Zhang
Keyword(s):  
Structural Characterization ◽  
Water Solution ◽  
Corrosion Current ◽  
Immersion Test ◽  
Alloy Sheet ◽  
Al Alloy ◽  
Entire Surface ◽  
Corrosion Properties ◽  
The Matrix

2024-T6 Al alloy sheet s were modified by bis-[triethoxysilylpropyl] tetrasulfide (BTESPT) silane film to improve the corrosion resistance. Fourier-Transform Reflection Absorption (FTIR-RA) spectroscopy was used for structural characterization of BTESPT silane film formed on surface of the sheet. Potentiodynamic polarization and immersion test in 3.5% NaCl solution were used for evaluating the corrosion performances of the silane film. The results showed that the film formed after curing at 120 °C for 40 min was cross-linked through Si-O-Si and that it was covered on the entire surface of the sheet. The content of elements S and Si on the Al2CuMg particles is a little higher that of on the matrix. The strong peak at 1032 cm-1 indicated that the film was linked to the sheet by Si-O-Al. Compared to the untreated case, the corrosion current density of the sheet treated with the silane film was reduced by close to 2 orders. Treatment of BTESPT silane can provide about 670 h protection of corrosion for the sheet in 3.5% NaCl water solution.

scholarly journals Mechanical and Corrosion Properties of Mg-Based Alloys with Gd Addition

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1775 ◽  
Author(s):  
Aneta Kania ◽  
Ryszard Nowosielski ◽  
Agnieszka Gawlas-Mucha ◽  
Rafał Babilas
Keyword(s):  
Open Circuit Potential ◽  
Corrosion Potential ◽  
Orthopedic Implants ◽  
Corrosion Current ◽  
Medical Application ◽  
Open Circuit ◽  
Dendritic Microstructure ◽  
Corrosion Properties ◽  
Electrochemical Parameters ◽  
Mechanical And Corrosion Properties

Magnesium alloys with rare earth metals are very attractive materials for medical application because of satisfactory mechanical properties. Nevertheless, low corrosion resistance is an obstacle in the use of Mg alloys as resorbable orthopedic implants. The paper presents results of mechanical and corrosion properties of MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. Based on the microscopic observations it was stated that the studied alloys show a dendritic microstructure with interdendritic solute rich regions. The phase analysis reveals an occurrence of α-Mg and Mg2Ca, Ca2Mg6Zn3 phases that are thermodynamic predictions, and stated Mg26Zn59Gd7 phases in MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. The Mg26Zn59Gd7 phases are visible as lamellar precipitations along interdendritic regions. It was confirmed that an increase of Gd content from 1 to 3 wt. % improves ultimate tensile (Rm; from 74 to 89 MPa) and compressive strength (Rc; from 184 to 221 MPa). Moreover, the studied alloys are active in Ringer’s solution. They are characterized by an increase of corrosion potential (Ecorr) of about 150 mV in comparison with values of open circuit potential (EOCP). The best electrochemical parameters (e.g., corrosion current density, icorr, polarization resistance, Rp, and Ecorr) were obtained for the MgCa3Zn1Gd2 alloy.

INFLUENCE OF SURFACTANTS ON THE CORROSION PROPERTIES OF CHROMIUM-FREE ELECTROLESS NICKEL DEPOSIT ON MAGNESIUM ALLOY

2012 ◽  
Vol 19 (03) ◽  
pp. 1250025 ◽  
Author(s):  
JOTHI SUDAGAR ◽  
RUAN DEWEN ◽  
YAQIN LIANG ◽  
RASU ELANSEZHIAN ◽  
JIANSHE LIAN
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Electroless Nickel ◽  
Corrosion Current ◽  
Immersion Test ◽  
Electrochemical Polarization ◽  
Nickel Deposit ◽  
Corrosion Properties ◽  
Positive Direction ◽  
Polarization Test

Influence of surfactants on the corrosion properties of chromium-free electroless nickel deposit were investigated on AZ91D magnesium alloy. The corrosion tests were carried out by immersion test (1 M HCl) and electrochemical polarization test (3.5 wt% NaCl ). The surfactants in the electroless nickel bath increases the corrosion resistance properties of the deposit on the magnesium alloy. In addition, smoothness and amorphous plus nano-crystalline phase were increased and accounted for the significant corrosion resistance. As a consequence, the corrosion potential moved towards the positive direction and the corrosion current density decreased. The immersion tests also provided the same trend as that of electrochemical polarization test. On the whole, the study concluded that corrosion resistance was enhanced by including a surfactant in the electroless deposits on magnesium alloy.

scholarly journals Polyaniline/Palm Oil Blend for Anticorrosion of Mild Steel in Saline Environment

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Mohd Rashid ◽  
Suhail Sabir ◽  
Afidah A. Rahim ◽  
Umesh Waware
Keyword(s):  
Mild Steel ◽  
Palm Oil ◽  
Potentiodynamic Polarization ◽  
Protective Layer ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Open Circuit ◽  
Oxidation Potential ◽  
Physical Interaction ◽  
Transfer Resistance

The corrosion protective performance of polyaniline/palm oil (PAni-PO) blend coated on mild steel in 3% NaCl aqueous solutions has been evaluated by electrochemical methods, namely, open circuit potential (ocp), potentiodynamic polarization, and EIS spectroscopy. The surface of mild steel was covered by a dark green protective layer due to the physical interaction between the coating and steel. The permanent shifts of ocp and potentiodynamic polarization towards higher positive value of oxidation potential by about 800 mV and by a decrease in corrosion current density by sixfold in magnitude and an increase of 10 orders of magnitude in charge transfer resistance are due to protective coating.

YSZ-Reinforced Mg-Based Amorphous Composites: Processing, Characterisation & Corrosion

2014 ◽  
Vol 939 ◽  
pp. 122-129 ◽  
Author(s):  
Yong Sheng Wang ◽  
Ming Jen Tan ◽  
Beng Wah Chua ◽  
Emin Bayraktar
Keyword(s):  
Amorphous Matrix ◽  
Physiological Saline ◽  
Corrosion Current ◽  
Ion Release ◽  
Corrosion Properties ◽  
Electrochemical Testing ◽  
The Matrix ◽  
Physiological Saline Solution ◽  
Corrosion Behaviors ◽  
Composites Processing

MgZnCa amorphous matrix-based composites whereby reinforcing the matrix with suitable reinforcements to achieve enhanced mechanical, biomedical and anti-corrosion properties have been studied here. Here, MgZnCa-based composites have been developed with different amounts (0-25%wt) of yttria-stabilized zirconia (YSZ) reinforcement phase. The aim is to understand the corrosion behaviors of YSZ-reinforced MgZnCa-based composites in physiological saline solution. It is found that the incorporation of YSZ into amorphous MgZnCa matrix can cause crystallization of the amorphous matrix. The higher the YSZ introduced, the higher the degree of crystallization, and a fully crystalline matrix is obtained at a YSZ concentration of 25%. Electrochemical testing and ion release measurements, revealed that the composite with 8%YSZ possesses the smallest corrosion current density and the least ion release rate. Surface morphology analysis indicates a much stronger anti-corrosion ability of 8%YSZ-reinforced MgZnCa composite.

scholarly journals Stress Corrosion Behavior of AM50Gd Magnesium Alloy in Different Environments

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 616 ◽  
Author(s):  
Miao Yang ◽  
Xiaobo Liu ◽  
Zhiyi Zhang ◽  
Yulai Song
Keyword(s):  
Magnesium Alloy ◽  
Hydrogen Embrittlement ◽  
Stress Corrosion ◽  
Anodic Dissolution ◽  
Corrosion Behavior ◽  
Pure Water ◽  
Corrosion Current ◽  
Open Circuit ◽  
Distilled Water ◽  
Corrosion Properties

A new type of high strength corrosion-resistant magnesium alloy was prepared by adding 1% rare earth Gd to AM50 and then treated with hot extrusion method. The stress corrosion properties of the new materials in air, pure water, 0.5 mol/L NaCl, and 0.5 mol/L Na2SO4 solution were studied by the slow strain rate tensile (SSRT) test, in situ open circuit potential test, Tafel curve test, stereomicroscope, SEM, and EDS. The results showed the following. The stress corrosion sensitivity of the material in different environments was Na2SO4 > NaCl > distilled water > air. According to the Tafel curves measured at 0 and 100 MPa, the corrosion voltage decreased little and the corrosion current density increased rapidly under 100 Pa. This was because the film of the corrosion product ruptured to form a large cathode and a small anode, which resulted in a large instantaneous corrosion current. The mechanism of hydrogen embrittlement and anodic dissolution together affected the stress corrosion behavior of the alloy. In distilled water, hydrogen embrittlement played a major role, while in NaCl and Na2SO4 solution, hydrogen embrittlement and anodic dissolution were both affected. The direct reason of the stress corrosion crack (SCC) samples’ failure was the cracks expanding rapidly at the bottom of pit, which was caused by corrosion.

Study on the Impact of Welding on the Corrosion Properties of AA 6061 T6

2014 ◽  
Vol 575 ◽  
pp. 210-213
Author(s):  
Elsadig Mahdi ◽  
E. Eltai
Keyword(s):  
Pitting Corrosion ◽  
Heat Affected Zone ◽  
Open Circuit Potential ◽  
Welding Process ◽  
Corrosion Current ◽  
Open Circuit ◽  
Nacl Solution ◽  
Corrosion Properties ◽  
The Impact ◽  
Alloy 6061

Aluminium alloy 6061 T6 circular specimens were joined using TIG welding method. AlMg5 was used as filler. The corrosion behavior of welded and un-welded AA 6061 T6 was investigated using potentiodynamic and open circuit potential (OCP) measurements. Specimens were immersed in 3.5 (wt %) NaCl solution. Different zones with different corrosion properties were created as a result of the welding process. Results reveals that sever pitting corrosion has taken place on the heat affected zone (HAZ); the corrosion current of HAZ was increased. The measured potential of HAZ was more negative and largely fluctuated comparing to base metal (BM).

The Chemical Deposition of Polypyrrole at a Copper Surface Varying Concentrations of Salicylic Acid in the Reactive Medium

2020 ◽  
Vol 1012 ◽  
pp. 447-452
Author(s):  
Andrea Santos Liu ◽  
Evelise Machado Ferri da Silva ◽  
Liu Yao Cho
Keyword(s):  
Salicylic Acid ◽  
Corrosion Potential ◽  
Chemical Deposition ◽  
Protective Layer ◽  
Corrosion Current ◽  
Copper Surface ◽  
Ethanol Solution ◽  
Positive Direction ◽  
Reactive Medium ◽  
Positive Displacement

The in situ chemical deposition of polypyrrole (Ppy) in presence of different concentrations of salicylic acid (SA) directly at copper 99.9% surface in ethanol solution using hydrogen peroxide as catalyst was studied. In all the concentrations, 50.0, 25.0, 12.5 and 6.25 mmol L-1 the polymerization was possible. The layer formed on the copper surface showed to be adherent and homogeneous. Its morphology presented as compact microspheres. The polarization curves showed a positive displacement in the corrosion potential of copper with undoped Ppy when compared to the polished copper surface. Copper surfaces containing doped Ppy-SA also showed an increase to the positive direction in the corrosion potential and the corrosion current density decreases more sharply in the presence of SA as dopant. These results indicated that Ppy+SA can act as a protective layer on copper surface and improve the corrosion protection. The protection efficiency of the coating was Cu surface < Cu+Ppy < Cu+Ppy+SA 50.0 < Cu+Ppy+SA 25.0 < Cu+Ppy+SA 12.5 < Cu+Ppy+SA 6.25 mmol L-1.

scholarly journals Assessment of corrosion resistance of cast cobalt- and nickel-chromium dental alloys in acidic environments

2017 ◽  
Vol 16 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Sven Mercieca ◽  
Malcolm Caligari Conti ◽  
Joseph Buhagiar ◽  
Josette Camilleri
Keyword(s):  
Corrosion Resistance ◽  
Inductively Coupled Plasma ◽  
Artificial Saliva ◽  
Base Material ◽  
Corrosion Current ◽  
Open Circuit ◽  
Cobalt Chromium ◽  
Corrosion Properties ◽  
Inductively Coupled ◽  
Nickel Chromium

Background: The aim of this study was to compare the degradation resistance of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys used as a base material for partial dentures in contact with saliva. Methods: Wiron® 99 and Wironit Extra-Hard® were selected as representative casting alloys for Ni-Cr and Co-Cr alloys, respectively. The alloys were tested in contact with deionized water, artificial saliva and acidified artificial saliva. Material characterization was performed by X-ray diffractometry (XRD) and microhardness and nanohardness testing. The corrosion properties of the materials were then analyzed using open circuit potential analysis and potentiodynamic analysis. Alloy leaching in solution was assessed by inductively coupled plasma mass spectrometry techniques. Results: Co-Cr alloy was more stable than the Ni-Cr alloy in all solutions tested. Leaching of nickel and corrosion attack was higher in Ni-Cr alloy in artificial saliva compared with the acidified saliva. The corrosion resistance of the Co-Cr alloy was seen to be superior to that of the Ni-Cr alloy, with the former exhibiting a lower corrosion current in all test solutions. Microstructural topographical changes were observed for Ni-Cr alloy in contact with artificial saliva. The Ni-Cr alloy exhibited microstructural changes and lower corrosion resistance in artificial saliva. The acidic changes did not enhance the alloy degradation. Conclusions: Ni-Cr alloys are unstable in solution and leach nickel. Co-Cr alloys should be preferred for clinical use.

Effects of Ti-1023 Anodized Coating on Corrosion Behavior of Ti-1023/30CrMnSiA and Ti-1023/LY12 Galvanic Couples

2007 ◽  
Vol 546-549 ◽  
pp. 1821-1826
Author(s):  
Jian Hua Liu ◽  
Jun Xiu Shi ◽  
Song Mei Li ◽  
Jun Lan Yi
Keyword(s):  
Corrosion Potential ◽  
Galvanic Corrosion ◽  
Corrosion Current ◽  
Optical Microscope ◽  
Open Circuit ◽  
Corrosion Properties ◽  
Corrosion Morphology ◽  
Average Value ◽  
Galvanic Couples ◽  
Corrosion Mechanisms

Galvanic properties were evaluated on bare and anodized Ti-1023 titanium alloy which coupled to Ni-electroplated, Zn-electroplated, Cd-electroplated 30CrMnSiA and anodized LY12, respectively. Corrosion properties including open circuit potential (Eoc) of each material, galvanic corrosion potential (Eg), and corrosion current (Ig) of the couples were monitored in conjunction with a Model 263A potentiostat system. Corrosion current density (Īg) and average value of corrosion potential (Ēg) were calculated from Ig-time and Eg-time curves, respectively. Corrosion morphology was observed on a optical microscope (OM) and corrosion mechanisms were analyzed and discussed. The corrosion resistance of Ti-1023/LY12 couple was significantly improved by Ti-1023 anodized coating. However, the coating accelerated the dissolve of the three electroplated coatings in the other galvanic couples, resulting in a heavy corrosion attack on 30CrMnSiA steel.

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