Hot Corrosion of Nimonic 105 in Sodium Sulfate-Sodium Chloride Melts

CORROSION ◽  
1981 ◽  
Vol 37 (7) ◽  
pp. 392-407 ◽  
Author(s):  
C. A. C. Sequeira ◽  
M. G. Hocking
Keyword(s):  
Sodium Chloride ◽  
Corrosion Behavior ◽  
Analytical Methods ◽  
Sodium Sulfate ◽  
Hot Corrosion ◽  
Corrosion Potential ◽  
Free Corrosion Potential ◽  
Chloride Melts ◽  
Ni Alloy ◽  
Potential Decay

Abstract The corrosion behavior of Nimonic 105 in molten Na2SO4, NaCl, and mixtures of these two salts, at 900 C, in laboratory air and under O2 + SO2/SO3 atmospheres has been evaluated by potentiodynamic, potential decay, and free corrosion potential measurements. In addition, the corrosion products were examined using several electron-optical techniques, and by other analytical methods. Pure Na2SO4 in air did not seem to be very corrosive towards Nimonic 105. Addition of NaCl to the molten Na2SO4 resulted in increased dissolution of Nimonic 105, which was in general nonuniform, alloy constituents nickel and cobalt dissolving more than others. Evidence of internal attack and enhancement of dissolution of the Ni alloy by SO3 was significant only when the corrosion conditions were prolonged. In pure NaCl, catastrophic corrosion occurs, which has been attributed to the depletion, dissolution, and vaporization of some alloy species.

scholarly journals Peculiarities in structure formation and corrosion of cast quasicrystalline Al63Cu25Fe12 and Al63Co24Cu13 alloys in sodium chloride aqueous solution

2020 ◽  
Vol 21 (3) ◽  
pp. 530-536
Author(s):  
O. V. Sukhova ◽  
V. A. Polonskyy
Keyword(s):  
Sodium Chloride ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Corrosion Potential ◽  
Corrosion Current ◽  
Corrosion Properties ◽  
Free Corrosion Potential ◽  
X Ray ◽  
Marine Climate ◽  
Potentiodynamic Method

In this work the structure and corrosion behavior of quasicrystalline cast Al63Cu25Fe12 and Al63Co24Cu13 alloys in 5-% sodium chloride solution (рН 6.9–7.1) were investigated. The alloys were cooled at 5 К/s. The structure of the samples was studied by methods of quantitative metallography, X-ray analysis, and scanning electron microscopy. Corrosion properties were determined by the potentiodynamic method. The made investigations confirm the formation of stable quasicrystalline icosahedral (y) and decagonal (D) phases in the structure of Al63Cu25Fe12 and Al63Co24Cu13 alloys correspondingly. In 5-% sodium chloride solution, the investigated alloys corrode under electrochemical mechanisms with oxygen depolarization. Compared with Al63Cu25Fe12 alloy, Al63Co24Cu13 alloy has a less negative value of free corrosion potential (–0.43 V and–0.66 V, respectively), and its electrochemical passivity region extends due to the inhibition of anodic processes. A corrosion current density, calculated from (E,lgi)-curve, for Al63Co24Cu13 alloy amounts to 0.18 mА/сm2 and for Al63Cu25Fe12 alloy – to 0.20 mА/сm2. The lower corrosion resistance of Al63Cu25Fe12 alloy may be explained by the presence of iron-containing phases in its structure. Based on obtained results, the Al63Co24Cu13 alloy was recommended as a coating material for rocket-and-space equipment working in a marine climate.

Influence of anodic coatings on stress corrosion behaviour of 7017 aluminium alloy

2013 ◽  
Vol 61 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Panagiotis Spathis
Keyword(s):  
Sodium Chloride ◽  
Aluminium Alloy ◽  
Aluminium Alloys ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Corrosion Potential ◽  
Nacl Solution ◽  
Free Corrosion Potential ◽  
Content Type ◽  
Dry Air

Purpose – The purpose of this work was to study the cracking susceptibility of a 7017 aluminium alloy, after anodising under various conditions. Design/methodology/approach – Slow strain tests in dry air, laboratory air and sodium chloride solution were employed. Anodic oxide films were produced with various applied current densities and thicknesses, in horizontal or vertical orientation of the coatings, at the free corrosion potential and also at various anodic or cathodic potentials. For the interpretation of the results, a metallographic study of the specimens before and after straining to failure was carried out using a scanning electron microscope. Findings – The behaviour of anodic coatings was found to depend very much on the anodising conditions. The coatings reduced the ductility of the alloy in dry air but can actually increase the ductility in laboratory air and in 3.5 per cent sodium chloride solution. In most cases, the ductility of coated specimens was greater in 3.5 per cent NaCl solution than in dry air, possibly due to crack blunting by the aggressive environment. Anodic coatings moved the free corrosion potential of the alloy in the noble direction and both the anodised and the bare alloy generally suffered a reduction in ductility at potentials anodic or cathodic to the free corrosion potential, the fall being more rapid for the anodised alloy. Research limitations/implications – The mechanism causing the increased ductility of coated specimens in 3.5 per cent NaCl solution than in dry air remains yet to be confirmed. Practical implications – The selection of suitable anodic coatings for the protection of aluminium alloys against stress corrosion cracking depends on the anodising conditions. Originality/value – The paper provides information regarding the influence of anodising conditions on the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.

scholarly journals Corrosion of WC-VC-Co Hardmetal in Neutral Chloride Containing Media

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
C. N. Machio ◽  
D. S. Konadu ◽  
J. H. Potgieter ◽  
S. Potgieter-Vermaak ◽  
J. Van der Merwe
Keyword(s):  
Corrosion Resistance ◽  
Sodium Chloride ◽  
Chemical Composition ◽  
Corrosion Behavior ◽  
Mine Water ◽  
Analytical Methods ◽  
Anodic Polarization ◽  
Polarization Behavior

The effect of varying VC content on the corrosion behavior of WC-10 wt% Co hardmetals in sodium chloride (NaCl) and synthetic mine water (SMW) solutions has been investigated using anodic polarization scans and surface analytical methods. It is shown that the polarization behavior is active-pseudopassive in NaCl and active in SMW regardless of the VC content, while the corrosion resistance is poorer and independent of VC content in NaCl but better at high VC contents in SMW. The corrosion behavior of samples is explained using the effect of VC on the chemical composition of the binder.

Hot Corrosion of T122 and 347HFG Steels in Na2SO4 Salts at 800 and 900 °C

2013 ◽  
Vol 711 ◽  
pp. 128-133
Author(s):  
Chun Yu Xu ◽  
Dong Bok Lee
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Hot Corrosion ◽  
Oxide Scales ◽  
Good Corrosion Resistance ◽  
Ni Alloy

The T122 steel (ferritic Fe-Cr-W alloy) and 347HFG stainless steel (austenitic Fe-Cr-Ni alloy) were corroded in the Na2SO4salt at 800 and at 900 °C, and their hot corrosion behavior was studied. They displayed good corrosion resistance owing to the formation of the protective Fe3O4and (Fe0.6Cr0.4)2O3scales. These oxides effectively suppressed sulfidation by the Na2SO4salt. The oxide scales that formed were thin and loosely adherent. The displayed good corrosion resistance was mainly attributed to the large amount of Cr in the alloys.

Corrosion Behavior and Mechanism of a Cu-Ni Alloy in Marine Environment

2008 ◽  
Vol 385-387 ◽  
pp. 385-388
Author(s):  
Qing Fen Li ◽  
Chun Hui Li ◽  
Ying Jie Qiao
Keyword(s):  
Corrosion Behavior ◽  
Marine Environment ◽  
Pitting Corrosion ◽  
Polarization Resistance ◽  
Corrosion Potential ◽  
Corrosion Process ◽  
Sulfate Reducing ◽  
Sterile Seawater ◽  
Ni Alloy ◽  
Reducing Bacteria

The microbiological influenced corrosion (MIC) behavior of a marine pipeline Cu-Ni alloy in the sterile seawater and sulfate-reducing bacteria (SRB) solution was investigated. Results show that severe pitting corrosion appeared on the specimens in the SRB solution. The corrosion potential of specimen in the SRB solution was much lower than that in the sterile seawater and the polarization resistance of specimen in the SRB solution decreased quickly after a period immersion and became much lower than that in the sterile seawater. Besides, the results of EDS and XRD show that the content of element Ni and Fe of the Cu-Ni alloy decreased greatly and the high content of element S appeared after 30 days immersion in the SRB solution. It was concluded that the SRB accelerated the corrosion process of the Cu-Ni alloy greatly. The MIC mechanism of the alloy in marine environment is discussed.

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