Low Potential Pitting Corrosion of Ni-Cr-Fe Alloys in Chloride Plus Thiosulfate Solutions: Determination of Potential and Concentration Boundaries

CORROSION ◽  
10.5006/3562 ◽  
2020 ◽  
Vol 76 (8) ◽  
pp. 786-795
Author(s):  
Abraham A. Becerra Araneda ◽  
Mariano A. Kappes ◽  
Martín A. Rodríguez ◽  
Ricardo M. Carranza
Keyword(s):  
Pitting Corrosion ◽  
Chloride Ions ◽  
Aged Alloy ◽  
Electrochemical Tests ◽  
Alloy 800 ◽  
Chloride Threshold ◽  
Alloy 690 ◽  
Fe Alloys ◽  
Thiosulfate Concentration

Low potential pitting corrosion (LPPC) of Alloys 690 and 800 (UNS N06690 and N08800) was studied in neutral solutions, containing chloride ions from 0.1 M to 1 M and thiosulfate ions from 5 × 10−5 M to 10−3 M. LPPC occurred close to the corrosion potential (–0.25 VAg/AgCl) by a synergic effect of the chloride and thiosulfate ions. The threshold concentrations of aggressive species for LPPC occurrence were identified by potentiostatic tests with mechanical scratching of the surface, which yielded more conservative estimations compared to other electrochemical tests. The ranges of potential and concentration of chloride and thiosulfate where LPPC occurred and where it merged with the conventional chloride pitting were determined. The lowest threshold concentrations were measured in Alloy 800, with a lower Cr content than Alloy 690. Thermally-aged Alloys 800 and 690 had lower resistance to LPPC than the corresponding solution-annealed material. In 1 M chloride-based solutions, for aged Alloy 800, LPPC occurred at a thiosulfate concentration as low as 5 × 10−5 M; in 10−3 M thiosulfate-based solutions, the chloride threshold was 0.1 M. For thermally-aged alloys, pits propagated intergranulary in some experiments. In solutions with chloride and thiosulfate concentrations close to the threshold required for pitting, repassivation of LPPC was observed after a sustained period of pit growth, originally initiated by scratching the surface. Such a repassivation has not been reported before in the literature in chloride and thiosulfate solutions. Two possible explanations were presented for this phenomenon.

Selectivity coefficients of some simple and complex inorganic ions for Spheron DEAE

1984 ◽  
Vol 49 (10) ◽  
pp. 2349-2354 ◽  
Author(s):  
František Vláčil ◽  
Karel Koňák
Keyword(s):  
Ion Exchange ◽  
Mobile Phase ◽  
Dynamic Method ◽  
Precious Metals ◽  
Inorganic Ions ◽  
Chromatographic Determination ◽  
Chloride Ions ◽  
Chloro Complexes ◽  
Selectivity Coefficients

The selectivity coefficients of the nitrate and chloride ions and of anionic chloro complexes of Au(III), Rh(III), Pd(II), and Pt(IV) for ion exchange on Spheron DEAE in the chloride form are determined by the dynamic method. the complex anion species formed are identified and the ion exchange nature of the sorption of precious metals on this sorbent is confirmed based on the elution order of the precious metals as determined previously by the column chromatography on Spheron DEAE using hydrochloric acid as the mobile phase. The effect of the presence of perchlorate in the mobile phase during the liquid chromatography of precious metals and during the chromatographic determination of nitrate traces is explained.

scholarly journals Determination of the neutralization depth of concrete under the aggressive environment influence

2018 ◽  
Vol 33 ◽  
pp. 02010 ◽  
Author(s):  
Anastasia Morzhukhina ◽  
Stanislav Nikitin ◽  
Elena Akimova
Keyword(s):  
Reinforced Concrete ◽  
Chloride Ions ◽  
The Body ◽  
Chemical Plants ◽  
Reinforced Concrete Structure ◽  
Load Bearing Capacity ◽  
High Rise ◽  
Capacity Loss ◽  
Air Penetration

Aggressive environments have a significant impact on destruction of many reinforced concrete structures, such as high-rise constructions or chemical plants. For example, some high-rise constructions are equipped with a swimming pool, so they are exposed to chloride ions in the air. Penetration of aggressive chemical substances into the body of concrete contributes to acceleration of reinforced concrete structure corrosion that in turn leads to load bearing capacity loss and destruction of the building. The article considers and analyzes the main technologies for calculating penetration depth of various aggressive substances into the body of concrete. The calculation of corrosion depth was made for 50-year service life.

Flow injection spectrophotometric determination of calcium, phosphate and chloride ions in milk

The Analyst ◽  
1992 ◽  
Vol 117 (6) ◽  
pp. 1019 ◽  
Author(s):  
Ma Asunci�n Herrero ◽  
Julia Atienza ◽  
Angel Maquieira ◽  
Rosa Puchades
Keyword(s):  
Calcium Phosphate ◽  
Spectrophotometric Determination ◽  
Flow Injection ◽  
Chloride Ions

Pitting Corrosion Behaviour of Boron Added Modified 9Cr–1Mo Steel: Combined Effects of Alkali and Chloride Ions

2014 ◽  
Vol 68 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Namrata Upadhyay ◽  
M. G. Pujar ◽  
C. R. Das ◽  
Nanda Gopal Krishna ◽  
C. Mallika ◽  
...  
Keyword(s):  
Pitting Corrosion ◽  
Corrosion Behaviour ◽  
Chloride Ions ◽  
Combined Effects

La corrosion par piqûres d'aciers inoxydables austéno-ferritiques dans l'eau de mer synthétique

1996 ◽  
Vol 84 ◽  
pp. 23-30
Author(s):  
I. Trigui ◽  
H. Sidhom ◽  
C. Braham ◽  
J. Lédion
Keyword(s):  
Corrosion Resistance ◽  
Pitting Corrosion ◽  
Sea Water ◽  
Phase Behaviour ◽  
High Nitrogen ◽  
Electrochemical Tests ◽  
Analysis Techniques ◽  
Pitting Corrosion Resistance ◽  
Nitrogen Contents ◽  
Image Analysis Techniques

Duplex stainless steels crevice and pitting corrosion resistance in synthetic sea water is studied. Conventional electrochemical tests and image analysis techniques are used. Three commercial steels are examined. The forged material has the best behaviour, whereas cast materials, in spite of their high nitrogen contents, have a lower corrosion resistance. Micrographic studies show a good correlation between pittings distribution and inclusions distribution and reveal that gamma phase behaviour is more affected by inclusions. The metallurgic purity of products seems to be the most important parameter in this type of corrosion. Consequently, the PREN index is questionable in pitting corrosion grading of these steels because it does not take into acount the inclusions effect.

scholarly journals Characterization and Corrosion Resistance Behavior of Shape Memory Stainless Steel Developed by Alternate Routes

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
David Dias ◽  
Sandra Nakamatsu ◽  
Carlos Alberto Della Rovere ◽  
Jorge Otubo ◽  
Neide Aparecida Mariano
Keyword(s):  
Corrosion Resistance ◽  
Shape Memory ◽  
Dendritic Structure ◽  
Microstructural Characterization ◽  
Rolling Process ◽  
Chloride Ions ◽  
Secondary Phases ◽  
Electrochemical Tests ◽  
The Matrix ◽  
Routing Methods

The microstructural characterization and corrosion resistance behavior of Fe-Mn-Si-Cr-Ni alloy with shape memory effect was studied under different mechanical processing conditions and heat treatments, which were produced using conventional casting and routing methods to reduce costs and make production viable. Microstructural characterization was performed with electron microscopy and x-ray diffraction techniques, electrochemical tests with polarization, and thermogravimetry techniques. The cast condition presented a dendritic structure and the presence of the secondary phases: ferrite-δ and Chi-X phase. The heat treatment eliminated phases, reincorporated elements in the matrix, and increased the austenitic grain. After the hot rolling process, the alloy exhibited a refined microstructure with recrystallized austenitic grains. The heat-treated condition presented better oxidation resistance than the other conditions, while the hot-rolled condition showed repassivation of the pits, raising them to higher levels. All conditions presented low corrosion resistance in environments containing chloride ions.

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