摘要:

AbstractThe influencing effects of temperature, potential and electrolyte composition on the electrochemical behaviour of Inconel 600 in aqueous solutions are presented. Considering these effects the connection between the data have been obtained from chemo‐mechanical fracture investigation on CT‐samples in Part I of this paper and pitting corrosion are discussed. The results have shown that chloride ions depassivate the surfaces of cracks locally and hinder the formation of a new protective oxide layer on the fracture surfaces. Furthermore, chloride promotes the dissolution of metal and initiates the cracking, respectively. The resulting crevice corrosion promotes an increase of hydrogen absorption by the metal. The increase of the hydrogen content of the metal influences the mechanical fracture behaviour. Contrary, sulphateions inhibit the initiation of corrosion mainly due to a hinderance of chloride ions adsorption on active sites of the fracture surfaces. The initiation of localized corrosion in the crevice region may be stimulated by chromate ions formed by oxidation of chromium from the oxide layer or the base metal in oxygen containing soluti

ISSN:0947-5117    

DOI:10.1002/maco.19970480702

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractBeschichtungen werden weit verbreitet zum Schutz metallischer Werkstoffe gegen Korrosion eingesetzt. Um den Einfluß einer Lackierung auf das Schwingungsrißkorrosionsverhalten von Stählen zu untersuchen, wurden Proben aus 34 CrMo 4 im vergüteten sowie im salzbadnitrocarburierten Zustand einerseits, und Proben aus 16 MnCr 5 im einsatzgehärteten Zustand andererseits vergleichenden Umlaufbiegeuntersuchungen ohne bzw. mit Korrosionseinfluß unterzogen. Das Schwingungsrißkorrosionsverhalten der untersuchten Varianten wird signifikant durch die Beschichtung verbessert, wobei die nitrocarburierte Variante eine deutliche Überlegenheit gegenüber der anderen Varianten

ISSN:0947-5117    

DOI:10.1002/maco.19970480703

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractCorrosion behavior of Ni‐Cr‐Base commercial alloys has been investigated in an argon‐42.6% oxygen‐14.7% bromine gas mixture at 700°C which was one of the environments encountered in the UT ‐3 thermochemical water decomposition reaction process to produce hydrogen. The test alloys were Inconel 600, Hastelloy C‐276, Inconel 625, and Nimonic 80A.Two‐dimensional thermodynamic phase stability diagrams were constructed for nickel, chromium, iron, tungsten, cobalt, titanium, and aluminium to predict the condensed corrosion products that are stable with respect to the representative alloying elements when the alloy is exposed to the argon‐42.6% oxygen‐14.7% bromine gas mixture at 700°C. The oxides were thermodynamically stable phases with respect to the corresponding metals.Post‐reaction treatment of test alloys included discontinuous mass‐change measurements, scanning electron microscopy (SEM), electron probe micro‐analysis (EPMA) for morphological and compositional investigation of the corrosion products, and the X‐ray diffraction (XRD) for phase identification. XRD identified oxides and spinels as corrosion products but low‐melting metal bromides were also detected for all alloys with deleterious effects on high‐temperature properties of these alloys during exposure to the environment.The poor corrosion resistance of Inconel 600 and Hastelloy C‐276 was mainly caused by the cracking and spalling of iron and nickel‐rich oxides and further growth of various metal bromides beneath the oxide scale following prolonged exposure. Inconel 625 and Nimonic 80A alloys performed better than Inconel 600 and Hastelloy C‐276, mainly because of their aluminium al

ISSN:0947-5117    

DOI:10.1002/maco.19970480704

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractWe have found that some bacteria able to induce metallic corrosion were present in water cells used by heat pumps. After the appearence of different problems encountered on these installations, we have decided to study the behaviour of steels commonly used for casing. To reproduce short and long term corrosion, we have followed these materials during 18 months with different analyses at 3, 8 weeks and at 12 and 18 months.The two stainless steels (AISI 3041, and 430) have similar behaviour. On the other hand, the low carbon steel (NF F‐24) and the low alloyed steel (APS20A) present important similarities. DC and AC analysis show that E24 and APS20A have a complex behaviour. But both can be simulated by elementary electrical analogues as a one time constant circuit in the early stage and by a two nested time constant circuit after 18 months with a diffusional process (Warburg). SEM observations and X‐ray diffraction spectra have given important informations on the chemistry and the geometry of the surface (bacteria, crystal

ISSN:0947-5117    

DOI:10.1002/maco.19970480705

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe kinetics of internal chlorination of Ni‐based alloys between 400°C and 700°C were investigated by optical and scanning electron microscopy. Internal chlorination of Ni‐4Cr and Ni‐4Cr‐0.5Ce alloy occurred by formation of solid precipitates such as CrCl2, and CeCl3which are thermodynamically stable and have low vapor pressures at the temperatures within the alloy matrix. In the lower temperature range, the kinetics of internal chlorination nearly followed a parabolic rate law. The degree of internal chlorination increased with increasing temperature. In the higher temperature range, the internal attack was accompanied by the consumption of the alloy by volatilization. When the rate of internal chlorination equaled the rate of overall metal consumption, the depth of the internal chlorination zone would approach a steady state value. At high temperatures, where vaporization was predominant, the steady state depth of internal attack was even smaller than that at lower temperature. When an alloy specimen was subject to little volatilization, it showed more internal attack than when it was not, and v

ISSN:0947-5117    

DOI:10.1002/maco.19970480706

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper analyses the causes of the premature failure call welded AISI 316L stainless steel (ss) pipes which formed part of a sea water cooling circuit. The service time of the pipes was 8 months. The laboratory tests carried out consisted of metallography tests, δ‐ferrite determination, intergranular corrosion susceptibility, cyclic anodic polarization curves, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) and X‐ray photo‐electron spectroscopy (XPS). The study presents typical forms of microbial induced corrosion (MIC) in AISI 308L and 316L ss in contact with natural sea water. The research is completed with the performance of bacteriological tests which demonstrate that the bacteria which cause the localized corrosion are of the sulphate‐reducing genus “desulfovibrio” and the sulphide‐oxidizing g

ISSN:0947-5117    

DOI:10.1002/maco.19970480707

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480708

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480711

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480714

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19970480717

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY