ISSN:0947-5117    

DOI:10.1002/maco.19960470821

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19960470822

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19960470823

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19960470824

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0947-5117    

DOI:10.1002/maco.19960470827

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractAn Umhüllungsfehlstellen von kathodisch geschützten erdverlegten Rohrleitungen wird bei Korrosionsschäden häufig die Anwesenheit sulfatreduzierender Bakterien (SRB) festgestellt. In Laborversuchen wurde das Korrosionsverhalten von Stahl St 37 im Potentialbereich (−0,5 V>UCu/CuSo4>−1,27 V) und beim Ruhepotential in Gegenwart einer SRB‐haltigen Mischkultur untersucht. Zur Simulation realer Verhältnisse wurden die Versuche an Stahlproben in sandgefüllten Säulen durchgeführt, die kontinuierlich mit einer glucosehaltigen Mineralsalzlösung durchströmt wurden.Aufgrund der ermittelten Abtragungsgeschwindigkeiten war für die homogene Mischelektrode selbst bei freier Korrosion eine unmittelbare Korrosionsgefährdung durch SRB nicht abzuleiten. Es trat lediglich ein erhöhter Schutzstrombedarf im Vergleich zu sterilen Bedingungen auf. Die Wasserstoffpermeation durch den niedriglegierten Stahl war in Gegenwart SRB‐haltiger Mischkulturen gegenüber sterilen und H2S‐freien Bedingungen leicht erhöht. Aus den ermittelten Permeationsstromdichten ließ sich ableiten, daß bei Potentialen UCu/CuSo4<−0,85 V unter sulfatreduzierenden Bedingungen nicht mit einer wasserstoffinduzierten Werkst

ISSN:0947-5117    

DOI:10.1002/maco.19960470802

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractAs part of the project “Environmental Effects on Materials” a field exposure programme was begun in 1993 in Switzerland. The exposure sites were chosen near the stations of the National Air Pollution Monitoring Network (NABEL), where climatic data are also recorded. This work presents the results for unalloyed and weathering steel, zinc, hot dip galvanized steel, copper and aluminium specimens after 1 year outdoor exposure, i.e. in an early stage of material degradation.Gravimetric evaluation of the test specimens revealed large differences in material loss due to corrosion for the different test sites that could be correlated with the environmental parameters. A mass balance calculation revealed that for steel, zinc and galvanized steel a considerable portion of corrosion products was lost during the exposure period depending on the environmental conditions at the test site. The losses could be attributed to flake‐off processes for the steels. This was concluded from SEM micrographs. For the zinc samples the most likely mechanism is removal by dissolution and washing away of the corrosion products during rainfall. This is supported by a good correlation of zinc corrosion product loss with the amount of rainfall and the fact that sheltered specimens did not exhibit significant losses of corrosion products. These specimens, on the other hand, showed a considerable accumulation of sulphates, chlorides and nitrates indicating the important role of dry deposition for the adsorption of gaseous pollutants on the metal surface. Generally the corrosive attack was relatively severe and more localized for the sheltered samples although the average corrosion loss was smaller than for those with open exposure.Specimens that had been covered with snow for a longer period of time (exposure site in the mountains) exhibited higher material losses than could be expected from the air pollution situation and climatic data. They also showed a remarkable accumulation of corrosive species on their surface. This unexpected behaviour can be explained by a longer effective time of wetness (compared to the calculated value) and the accumulation of pollutants in the snow layer and on the metal surface.The statistical analysis of the corrosion loss data and the environmental parameters yielded good correlations with the average SO2‐concentration for the different test sites especially when the time of wetness and wind velocity were also taken into account. Sulfur dioxide plays a dominant role among the gaseous pollutants although its concentration could be reduced substantially during the last decade due to various measures taken to reduce sulfur emission. The effect of atmospheric nitrogen compounds (mainly nitrogen dioxide) and ozone for the corrosion of the different metals and the interaction of the different air pollutants is not yet completely understood and is still under investigation under defined conditions in a test chamber.The corrosion products found on different metals surfaces have been analysed using various techniques. Their composition could in some cases be related to the corresponding environmental conditions at the tes

ISSN:0947-5117    

DOI:10.1002/maco.19960470803

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractProgress on the area of passivation of metallic materials by polyaniline is being presented. The redoxcatalytic reaction leading to the formation of a passivating oxide layer has been evaluated, and a reaction scheme is shown. Results of corrosion tests are described as well.

ISSN:0947-5117    

DOI:10.1002/maco.19960470804

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effect of an environment containing chloride on the fatigue behaviour of a 8090 AlLiMgCu alloy was studied. Results were compared with those obtained on a traditional 2024 AlCuMg alloy. Fatigue and corrosion‐fatigue tests were carried out both on smooth specimens and riveted samples. In order to assess the corrosion behaviour of the materials and their susceptibility to stress corrosion cracking, potentiodynamic polarization and slow strain rate tests were carried out.Results showed a remarkable effect of the aggressive environment on the fatigue behaviour both of the innovative 8090 alloy (in T8 ageing conditions) and on the traditional clad 2024 alloy (in T3 natural ageing conditions), though the former showed slightly better behaviour. Nevertheless, in the presence of rivets the reduction in fatigue strength in the aggressive environment was negligible. Slow strain rate tests showed premature fractures under anodic polarization above the pitting potential and with a strain rate of 10−6s−1, only for th

ISSN:0947-5117    

DOI:10.1002/maco.19960470805

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractIn den letzten Jahren sind an geschweißten, verzinkten Stahlrohren in Trinkwasser‐Installationen gehäuft Korrosionsschäden an Schweißnähten aufgetreten. Ihrer Erscheinungsform wegen werden sie als Grabenkorrosion bezeichnet. Sie tritt auch in deckschichtbildenden Wässern auf und wird durch schwefelhaltige Blockseigerungen im Bandstahl verursacht. Betroffen sind lediglich ERW‐geschweißte Rohre ohne Nachbehandlung, meist mit Schwefelgehalten über 0,008%. Grabenkorrosion ließe sich zwar durch metallurgische Maßnahmen vermeiden. Dieser Weg ist jedoch kostspielig und schwer gangbar. Aus diesem Grunde wird der DVGW gebeten, den bisher registrierten Rohren mit einschlägigen Schwächen die Register‐Nummer zu entziehen. Die Anfälligkeit geschweißter Rohre gegenüber Grabenkorrosion kann durch Beizen mit Salz

ISSN:0947-5117    

DOI:10.1002/maco.19960470806

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY