scholarly journals Roles of Alloying Elements on the Passivity of W-xCr-yNi Alloys in Aggressive Environments

2014 ◽  
Vol 14 (2) ◽  
pp. 73-80
Author(s):  
PL Kharel ◽  
SP Sah ◽  
J Bhattarai
Keyword(s):  
Solid Solution ◽  
Corrosion Resistance ◽  
Synergistic Effect ◽  
Single Phase ◽  
Alloying Elements ◽  
Anodic Current ◽  
Ni Alloys ◽  
Current Densities ◽  
Sputter Deposited

The role of alloying elements on the passivity of the sputter−deposited amorphous or nanocrystalline W-xCr-yNi alloys in 12 M HCl, 0.5 M NaCl and 1 M NaOH solutions open to air at 30°C was studied by corrosion tests and electrochemical measurements. All the examined sputter-deposited W-(42-75)Cr-(4-15)Ni alloys, which are composed of either amorphous or nanocrystalline single phase solid solution, showed higher corrosion resistance than those of alloying elements (i.e. tungsten, chromium and nickel) in 12 M HCl, 0.5 M NaCl and 1 M NaOH solutions. All the alloys used in this study showed higher corrosion resistance than those of the alloying elements in the aggressive environments. Anodic current densities of the alloys decreased with increasing chromium contents and became lower than that of chromium. Transpassive dissolution of chromium was significantly enhanced by the simultaneous additions of tungsten, chromium and nickel in aggressive environments of 12 M HCl, 0.5 M NaCl and 1 M NaOH. Hence the synergistic effect of chromium addition in enhancing the corrosion resistance of the W-xCr-yNi alloys was clearly observed from the present study.DOI: http://dx.doi.org/10.3126/njst.v14i2.10418   Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 65-72

Corrosion of Fe-Cr and Fe-Cr-Ni Alloys at 700-800°C in CO2-0.3SO2-6O2 Mixed Gas

2020 ◽  
Vol 833 ◽  
pp. 85-89
Author(s):  
Min Jung Kim ◽  
Dong Bok Lee ◽  
Xiao Xiao ◽  
Kyong Hwan Lee
Keyword(s):  
Corrosion Resistance ◽  
Oxide Scale ◽  
Alloying Elements ◽  
Mixed Gas ◽  
Corrosion Rates ◽  
Ni Alloys

ASTM T22 (Fe-2.25Cr-1Mo), 347HFG (Fe-18Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels were reacted with CO2-0.3SO2-6O2 mixed gas. During corrosion at 700-800 °C for 20-100 h, 347HFG (Fe-18Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels had good protective Cr2O3 oxide scale. Corrosion rates increased progressively as the corrosion temperature and time increased. Corrosion resistance increased in the order of T22, 347HFG, and 310H, suggesting that the alloying elements of Cr and Ni beneficially improved the corrosion resistance of steels. Basically, Fe oxidized to Fe2O3, and Cr oxidized to Cr2O3, some of which further reacted with FeO to form FeCr2O4.

scholarly journals The Corrosion Behavior of Sputter-deposited W-Cr-(4-15)Ni Alloys in NaOH Solutions

1970 ◽  
Vol 24 ◽  
pp. 3-11
Author(s):  
Pom Lal Kharel ◽  
Jagadish Bhattarai
Keyword(s):  
Corrosion Resistance ◽  
Open Circuit Potential ◽  
Chromium Content ◽  
Chemical Society ◽  
Open Circuit ◽  
Ni Alloys ◽  
Ni Alloy ◽  
Naoh Solution ◽  
Order Of Magnitude ◽  
Sputter Deposited

The synergistic effect of chromium addition in the sputter-deposited amorphous or nanocrystalline W-Cr-(4-15)Ni alloys is studied in alkaline NaOH solutions at 25°C, open to air using immersion tests and electrochemical measurements. In 1 M NaOH solution, the addition of chromium to W-Cr-(4-15)Ni alloys containing 42-75 at % chromium increased the corrosion resistance and shifted the open circuit potential more noble so as to show higher corrosion resistance than those of alloy-constituting elements (that is, tungsten, chromium and nickel). The corrosion rates (that is, about 2-5 x 10-3 mm.y-1) of all the examined W-Cr-(4-15)Ni alloys are about two orders of magnitude lower than that of tungsten and nearly one order of magnitude lower than that of chromium metal. The open circuit potential of the W-Cr-(4-15)Ni alloys is generally increased with increasing chromium content in different concentrations of NaOH solutions. The passivity of the WCr-(4-15)Ni alloys is increased with decreasing the concentration of NaOH solutions at 25°C. Keywords: Corrosion resistance; Sputter deposition;  W-Cr-Ni alloy;  NaOH solution; Open Circuit  potential. DOI: 10.3126/jncs.v24i0.2380Journal of Nepal Chemical Society, Vol. 24, 2009 Page: 3-11

scholarly journals The Corrosion Behavior of Sputter-deposited Ternary Zr-(12-18)Cr-W Alloys in 12 M HCl Solution

1970 ◽  
Vol 26 ◽  
pp. 13-21 ◽  
Author(s):  
Jagadeesh Bhattarai
Keyword(s):  
Electrochemical Measurement ◽  
Dc Magnetron Sputtering ◽  
Anodic Current ◽  
Corrosion Resistant ◽  
Corrosion Rates ◽  
Current Densities ◽  
Sputter Deposited ◽  
Hcl Solution ◽  
Dissolution Current ◽  
Zirconium Addition

Ternary amorphous or/and nanocrystalline Zr-(12–18)Cr–W alloys were successfullyprepared by direct current (DC) magnetron sputtering. The corrosion rates of Zr-(12-18)Cr-W alloys are in the range of 1-2 x 10-3 mm/y which are even lower than those of thesputter-deposited binary W-Zr and W-Cr alloys, and are nearly one order of magnitudelower corrosion rate than those of the alloy-constituting elements in 12 M HCl at 30°C,open to air. All the examined sputter-deposited amorphous or/and nanocrystalline Zr-(12-18)Cr–W alloys are passivated spontaneously. The zirconium addition suppresses theanodic dissolution current, and hence the anodic current densities of the alloys decreasedwith increasing the zirconium content in the alloys. It is, therefore, considered that thesimultaneous additions of zirconium and tungsten with 12-18 at% of chromium enhancesynergistically the corrosion-resistant and pitting corrosion of the sputter-depositedZr-(12-18)Cr-W alloys in 12 M HCl.Keywords: Corrosion-resistant; Zr-Cr-W alloys; Electrochemical measurement; Pitting corrosionDOI: 10.3126/jncs.v26i0.3625Journal of Nepal Chemical SocietyVol. 26, 2010Page: 13-21

scholarly journals Conversion Coatings Produced on AZ61 Magnesium Alloy by Low-Voltage Process

2016 ◽  
Vol 61 (1) ◽  
pp. 419-424
Author(s):  
M. Nowak ◽  
B. Płonka ◽  
A. Kozik ◽  
M. Karaś ◽  
M. Mitka ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Electrochemical Method ◽  
Low Voltage ◽  
Anodic Oxide ◽  
Conversion Coatings ◽  
Anodic Current ◽  
Az61 Magnesium Alloy ◽  
Current Densities ◽  
Oxide Conversion

The resultes of anodic oxide conversion coatings on wrought AZ61 magnesium alloy production are describe. The studies were conducted in a solution containing: KOH (80 g/l) and KF (300 g/l) using anodic current densities of 3, 5 and 10 A/dm2 and different process durations. The obtained coatings were examined under a microscope and corrosion tests were performed by electrochemical method. Based on these results, it was found that the low-voltage process produces coatings conferring improved corrosion resistance to the tested magnesium alloy.

scholarly journals X-ray Photoelectron Spectroscopic Study on the Anodic Passivity of Sputterdeposited W-Ta Alloys in 12 M HCl

2012 ◽  
Vol 12 ◽  
pp. 139-148
Author(s):  
Jagadeesh Bhattarai
Keyword(s):  
Corrosion Resistance ◽  
Spectroscopic Study ◽  
Passive Films ◽  
Xps Analysis ◽  
X Ray ◽  
Quantitative Surface Analysis ◽  
Potentiostatic Polarization ◽  
Sputter Deposited ◽  
Hcl Solution

The role of a simultaneous additions of tungsten and tantalum on the anodic passivity of the passive films of the sputter-deposited nanocrystalline W-xTa alloys was studied using immersion tests, electrochemical measurements and X-ray photoelectron spectroscopic (XPS) analysis. The formation of spontaneous passive film on the alloys, which is composed of double oxyhydroxide of tungsten and tantalum ions are responsible for their higher corrosion resistance than those of the alloy-constituting elements in 12 M HCl solution open to air at 30°C. The quantitative surface analysis by XPS is clarified that the improved anodic passivity of the alloys than those of alloy-constituting elements is based on the formation of new anodic passive oxyhydroxide films composed of W6+ and Ta5+ ions. These films have higher protectiveness and stability than those of passive oxyhydroxide films of alloy-constituting elements, that is, oxyhydroxides of hexavalent tungsten and pentavalent tantalum after potentiostatic polarization for 1 h in 12 M HCl.DOI: http://dx.doi.org/10.3126/njst.v12i0.6492 Nepal Journal of Science and Technology 12 (2011) 139-148 

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