京都大学 / 新制・課程博士 / 博士(工学) / 甲第23483号 / 工博第4895号 / 新制||工||1765(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 清野 純史, 教授 八木 知己 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

La compréhension des mécanismes de la corrosion atmosphérique sous abri à très long terme des alliages ferreux concerne plusieurs applications. D'une part, l'emploi massif du fer dans l'architecture médiévale pose, notamment, la question de l'évolution à long terme de ce matériau dans ces conditions. D'autre part, la période d'entreposage, lors du processus de traitement des déchets nucléaires, pointe le besoin d'une modélisation sur plusieurs centaines d'années du comportement des aciers doux, matériau envisagé pour les sur-containers. Une approche commune a été développée pour ces deux problématiques et appliquée sur le chaînage de renfort métallique de la cathédrale d'Amiens (XVe siècle). La corrosion atmosphérique sous abri à long terme est contrôlée par un cycle d'humidification à séchage, durant lequel la couche oxydée joue un rôle. Le premier axe de travail a donc consisté à caractériser finement le système de corrosion, à l'aide d'un croisement de techniques, depuis l'échelle macroscopique jusqu'à l'échelle nanométrique. L'accent a été en particulier mis sur les techniques d'analyse structurale micro-focalisées (μ-Raman, μ-DRX et μ-XAS), qui permettent de déterminer la nature des phases présentes, leur localisation et leurs proportions. Le système de corrosion est composé du milieu environnant, de la couche de produits de corrosion et du substrat métallique. Les couches de produits de corrosion sont constituées d'une matrice de goethite nanocristallisée, contenant de faibles quantités de lépidocrocite et d'akaganéite, ces deux phases étant principalement situées en couche externe. De plus, des marbrures plus claires sont observées au sein de la matrice. Parfois composées de maghémite, ces marbrures sont principalement constituées de ferrihydrite/feroxyhite et peuvent être connectées, ou non, au substrat métallique. Dans le second axe de travail, des expériences spécifiques ont été conduites pour tester certaines hypothèses de mécanismes liées au cycle humidification-séchage. En ce sens, les sites de réduction de l'oxygène ont été localisés en milieu insaturé et plusieurs cas ont été mis en évidence, fonction de la morphologie de la couche corrodée. Par ailleurs, des expériences en cellule électrochimique couplée avec des techniques d'analyse structurale ont permis de suivre in situ la réduction de composés de référence modèles. Ce couplage a montré l'influence du mode de réduction et du pH du milieu sur la nature de la ou des phases formées. L'ensemble de ces résultats a conduit à proposer un ensemble de mécanismes pour la corrosion atmosphérique sous abri du fer à très long terme, incluant la morphologie des couches de produits de corrosion et les propriétés des phases en présence. Ces différentes hypothèses ont été intégrées dans une proposition de méthode de diagnostic de la stabilité des systèmes ferreux anciens, mais elles permettent également de discuter les modélisations existantes de la corrosion atmosphérique. / Understanding the mechanisms of indoor atmospheric corrosion in iron alloys is of primary importance in several fields, including for the conservation of Middle Ages monuments or the long term storage of nuclear waste. In this research, a double approach was developed, combining fine characterisation of corrosion systems and design of experiments to answers specific questions related to mechanisms understanding. Iron indoor atmospheric corrosion was investigated on samples coming from the reinforcing chain of the Amiens cathedral (15th century). In the first stage, the corrosion system has been extensively characterised from the macroscopic to the nanometric scale. In particular, structural micro-analysis (μ-Raman, μXRD, μXAS) has been used to locate, identify and quantify the oxidised phases. Rust layers are composed of a matrix of nanometric goethite, with low quantities of lepidocrocite and akaganeite mostly located in the extern part of the corrosion system. In addition, clear marblings are dispersed in the matrix, which are sometimes connected with the metal core. Although these may contain maghemite, these marblings are generally made of ferrihydrite/feroxyhite phases. In the second stage, specific experiments have been carried out in an unsaturated marked medium to locate oxygen reduction sites in the rust layers. Several cases were evidenced, depending on the rust layer morphology. In addition, reduction processes of model phases have been studied in situ, using an electrochemical cell coupled with structural characterisation techniques. This combination highlighted the influence of reduction mode and pH on the type of reduced phase formed. From the obtained results, several mechanisms are proposed to explain the long term indoor atmospheric corrosion of iron, including rust layers morphology and phases properties. The different hypotheses have been integrated in a proposed method to diagnosis ancient ferrous systems stability. These hypotheses also provide a discussion ground for existing modelling of atmospheric corrosion.

Re-processed oxide fuel product from the Thermal Oxide Reprocessing Plant (THORP) is stored in Type 316L stainless steel, using a design of several nested cans, with the outer can providing the safety case containment barrier. The research reported in this PhD thesis aims to support the safety case related to these storage cans, by identifying and characterising susceptible microstructure sites and associated material surface conditions. The overarching goal of this project is to understand the propensity of THORP storage cans towards localised corrosion and Environment Assisted Cracking (EAC) in HCl and chloride-bearing atmospheric environments. The investigation focused on two possible corrosion cases: (1) understanding the effect of surface finishing on material performance in chloride-containing atmospheric environments, and (2) characterising the effects of the HCl aqueous solutions inside the can, with potential formation of HCl vapour. Microstructure investigations were carried out on surface-treated type 316L coupon specimens. The application of aqua blasting resulted in a deformed near-surface microstructure, containing compressive residual stresses to a depth of 100-120 micrometres. Subsequent laser engraving produced a recrystallized surface layer with tensile residual stresses reaching to a depth of 200 micrometres. Changes of surface roughness topography were accompanied by the development of a thick oxide/hydroxide film after laser engraving. Atmospheric exposure revealed similar corrosion attack for all samples, with laser engraving exhibiting the lowest number of corrosion sites, but with the largest average depth of attack. In addition, laser engraving led to atmospheric-induced stress corrosion cracking (AISCC) within two weeks of exposure to 386 ug/cm2 MgCl2-laden droplet deposits, with crack growth rates similar to ground U-bend samples. Strategies to reduce the likelihood of AISCC of laser-engraved components are discussed. The influence of HCl concentration and exposure temperature on the corrosion type and rate of annealed and cold rolled type 316L stainless steel has also been investigated. Cold rolling of up to 20 % reduction was introduced, with potentio-dynamic polarization measurements conducted in 0.01 - 3 M HCl aqueous solution. Results are compared to microstructures immersed under open circuit conditions, and to HCl-laden droplet deposits at temperatures up to 80C. Corrosion type diagrams are introduced to describe the transition between uniform corrosion, mixed-mode uniform with pitting corrosion, and pitting corrosion only, as a function of temperature, HCl concentration, and cold deformation. SCC tests of type 316L stainless steel have been carried out at 110C, by exposing U-Bend samples to HCl-laden droplets and HCl vapour. The humidity of the environment was controlled using defined volume fractions of H2O in a sealed environmental chamber. HCl-laden droplets with chloride deposition densities exceeding 1.5 ug/cm2 led to SCC after 90 minutes of exposure, whereas no corrosion attack was observed for samples with exposure to 0.15 ug/cm2 HCl. Increasing HCl concentrations resulted in fewer, but longer cracks, reaching up-to several hundreds of micrometres in length. HCl vapour exposure was carried out by adding various volumes of HCl solution in a beaker to the sealed test chambers. These HCl vapour tests confirmed a change of corrosion type with HCl concentration, from pitting corrosion with SCC, to the occurrence of uniform corrosion.

Made available in DSpace on 2016-12-08T17:19:37Z (GMT). No. of bitstreams: 1 Parte 1.pdf: 175711 bytes, checksum: 4c45110c54dab616ccb4e24cf3e91d86 (MD5) Previous issue date: 2011-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In coastal and in industrial region the atmosphere is considered aggressive due to the high relative humidity, and also due to the presence of chloride ions (Cl־) and sulphate (SO4 -²)ions, accelerating the corrosion process to accelerate. This onerous on electric distribution companies due to direct costs, because even the galvanized metal components must be replaced often, and indirect costs such as disruption of electricity supply for maintenance. Thus, the aim of this work, together with CELESC SA (Electric Centrals of Santa Catarina), was to study the atmospheric corrosion of the galvanized steel used in electric distribution networks in the south coast of Santa Catarina. For this it was installed 10 different locations, monitoring stations of atmospheric parameters to measure the rate of sulfate, chloride and sedimentary particles in a period of six months. The zinc layer applied to the SAE 1010 steel plates used in corrosion tests were characterized by optical and electron microscopy. The corrosion products formed on the surface of galvanized steel in corrosion tests were characterized by X-ray diffraction and scanning electron microscopy. The results indicated that most of the locations had a high rate of corrosion, classified according to ISO 9223 as C5. The variations in the chloride content per month were attributed to the wind direction. The Simonkolleite (Zn5(OH)8Cl2.H2O) was the main corrosion product formed on the galvanized steel, due to the presence of chloride in the air at all monitoring stations. This product was also observed in salt spray corrosion tests. / Em regiões litorâneas e industriais a atmosfera é considerada agressiva devido à umidade relativa ser elevada, e também devido à presença de íons de cloreto (Cl־) e de sulfato (SO4 -²), fazendo com que o processo de corrosão seja acelerado. Isso onera as empresas de distribuição de energia elétrica devido aos custos diretos, pois freqüentemente componentes metálicos mesmo galvanizados devem ser substituídos, e custos indiretos como interrupções do fornecimento de energia elétrica para manutenção. Sendo assim, o objetivo principal deste trabalho, vinculado a CELESC S.A. (Centrais Elétricas de Santa Catarina) foi estudar a corrosão atmosférica em aço galvanizado empregado em redes de distribuição de energia elétrica no litoral sul de Santa Catarina. Para isto foram instaladas em 10 locais diferentes, estações de monitoramento de parâmetros atmosféricos, tais como, taxa de sulfatação, teor de cloretos e partículas sedimentáveis em um período de seis meses. A camada de zinco aplicada nas placas de aço SAE 1010 utilizadas nos ensaios de corrosão foi caracterizada por meio de microscopia óptica e eletrônica. Os produtos de corrosão formados na superfície do aço galvanizado nos ensaios de corrosão foram caracterizados por difração de raios-X e microscopia eletrônica de varredura. Os resultados indicaram que a maioria dos locais apresentou alto índice de corrosividade, classificado segundo a norma ISO 9223 como C5. As variações nos valores de teor de cloretos mensais foram atribuídas à direção dos ventos. O Simonkolleite (Zn5(OH)8Cl2.H2O) foi o principal produto de corrosão formado sobre o aço galvanizado, devido à presença de cloretos no ar em todas as estações de monitoramento. Esse produto também foi encontrado nos ensaios de corrosão em névoa salina.

No description available.

An extensive investigation with parallel field andlaboratory exposures has been conducted to elucidateatmospheric corrosion and metal runoff processes on copper andzinc used for roofing applications. Detailed studies have beenperformed to disclose the effect of various parameters on therunoff rate including: surface inclination and orientation,natural patination (age), patina composition, rain duration andvolume, rain pH, and length of dry periods inbetween rainevents. Annual and average corrosion rates and runoff rateshave been determined consecutively during urban field exposuresin Stockholm on naturally patinated copper and zinc of varyingage and patina composition. The corrosion rate was found todecrease with time, amounting to 6.7 g Cu/(m2.y) and 5.0 gZn/(m2.y) after 48 weeks of exposure, whereas the runoff ratewas relatively constant with time on a yearly basis, being 1.3g/(m2.y) and 3.1 g/(m2.y) for copper and zinc, respectively.The annual runoff rate was found to be significantly lower thanthe corresponding corrosion rate for both copper and zinc.Somewhat higher runoff rates of copper were determined fromnaturally green-patinated copper (&gt;40 years old, 2.0g/(m2.y)) compared to brown-patinated copper (1 year old). Themain reasons are specific environmental conditions combinedwith characteristics of the patina layer, which increase themagnitude of dissolved species flushed from the surface duringthe first flush volume of a rain event. No intrinsic effect ofpanel age on the runoff rate was seen for naturally patinatedzinc. However, differences in prevailing environmentalconditions during the initial exposure period and, hence,differences in formation rate and surface coverage of thecorrosion patina, resulted in variations in runoff rate. Thisinitial difference remained also during prolonged exposureperiods and was referred to as a memory effect. Model roof investigations and laboratory studies showedsurface orientation and inclination to have a detrimentaleffect on the runoff rate with high runoff rates from surfacesof low inclination from horizon and surfaces exposed towardsthe wind direction. Based on fieldexposures and literature data, a correlationwas established between the runoff rate and the prevailingSO2-concentration. The runoff rate increases with increasingSO2 level for exposure sites of similar annual precipitationquantities (500-1000 mm/y). A rain device, using artificialrain, was shown to successfully simulate outdoor rain events ofvarying intensity and pH and result in realistic runoff ratesof both copper and zinc. The device was used to monitor changesin metal concentration and quantity of runoff water duringindividual rain events. High metal concentrations are found inthe initial rain volume flushing the surface (first flush),which decreased to rather constant metal concentrations duringthe subsequent rain volume (steady-state). The magnitude offirst flush depends primarily on environmental conditions priorto a rain event and the characteristics of the corrosionpatina. The metal concentration in runoff water increases withrain acidity, decreases with rain intensity and increases withlength of the dry period preceding a rain event. A comparison between instantaneous corrosion rates,monitored by electrochemical impedance spectroscopy using a2-electrode set-up, and runoff rates during a continuous rainevent was performed for naturally patinated copper panels.Corrosion rates were found to be approximately 10 (brownishpatina) and 25 times (greenish patina) lower than correspondinginstantaneous runoff rates. A schematic description of the first flush and steady-stateregion of the runoff process was established. The magnitude ofthe concentration during first flush is primarily affected byprevailing environmental conditions prior to a rain event,while rain pH and intensity primarily affect the concentrationduring steady-state. <b>Key words:</b>atmospheric corrosion, corrosion rate, runoffrate, copper, zinc, field study, laboratory study, roof, firstflush, rain quantity, rain intensity, rain pH, dry and wetdeposition, corrosion and runoff process.

No description available.

<p>An extensive investigation with parallel field andlaboratory exposures has been conducted to elucidateatmospheric corrosion and metal runoff processes on copper andzinc used for roofing applications. Detailed studies have beenperformed to disclose the effect of various parameters on therunoff rate including: surface inclination and orientation,natural patination (age), patina composition, rain duration andvolume, rain pH, and length of dry periods inbetween rainevents. Annual and average corrosion rates and runoff rateshave been determined consecutively during urban field exposuresin Stockholm on naturally patinated copper and zinc of varyingage and patina composition. The corrosion rate was found todecrease with time, amounting to 6.7 g Cu/(m2.y) and 5.0 gZn/(m2.y) after 48 weeks of exposure, whereas the runoff ratewas relatively constant with time on a yearly basis, being 1.3g/(m2.y) and 3.1 g/(m2.y) for copper and zinc, respectively.The annual runoff rate was found to be significantly lower thanthe corresponding corrosion rate for both copper and zinc.Somewhat higher runoff rates of copper were determined fromnaturally green-patinated copper (>40 years old, 2.0g/(m2.y)) compared to brown-patinated copper (1 year old). Themain reasons are specific environmental conditions combinedwith characteristics of the patina layer, which increase themagnitude of dissolved species flushed from the surface duringthe first flush volume of a rain event. No intrinsic effect ofpanel age on the runoff rate was seen for naturally patinatedzinc. However, differences in prevailing environmentalconditions during the initial exposure period and, hence,differences in formation rate and surface coverage of thecorrosion patina, resulted in variations in runoff rate. Thisinitial difference remained also during prolonged exposureperiods and was referred to as a memory effect.</p><p>Model roof investigations and laboratory studies showedsurface orientation and inclination to have a detrimentaleffect on the runoff rate with high runoff rates from surfacesof low inclination from horizon and surfaces exposed towardsthe wind direction.</p><p>Based on fieldexposures and literature data, a correlationwas established between the runoff rate and the prevailingSO2-concentration. The runoff rate increases with increasingSO2 level for exposure sites of similar annual precipitationquantities (500-1000 mm/y). A rain device, using artificialrain, was shown to successfully simulate outdoor rain events ofvarying intensity and pH and result in realistic runoff ratesof both copper and zinc. The device was used to monitor changesin metal concentration and quantity of runoff water duringindividual rain events. High metal concentrations are found inthe initial rain volume flushing the surface (first flush),which decreased to rather constant metal concentrations duringthe subsequent rain volume (steady-state). The magnitude offirst flush depends primarily on environmental conditions priorto a rain event and the characteristics of the corrosionpatina. The metal concentration in runoff water increases withrain acidity, decreases with rain intensity and increases withlength of the dry period preceding a rain event.</p><p>A comparison between instantaneous corrosion rates,monitored by electrochemical impedance spectroscopy using a2-electrode set-up, and runoff rates during a continuous rainevent was performed for naturally patinated copper panels.Corrosion rates were found to be approximately 10 (brownishpatina) and 25 times (greenish patina) lower than correspondinginstantaneous runoff rates.</p><p>A schematic description of the first flush and steady-stateregion of the runoff process was established. The magnitude ofthe concentration during first flush is primarily affected byprevailing environmental conditions prior to a rain event,while rain pH and intensity primarily affect the concentrationduring steady-state.</p><p><b>Key words:</b>atmospheric corrosion, corrosion rate, runoffrate, copper, zinc, field study, laboratory study, roof, firstflush, rain quantity, rain intensity, rain pH, dry and wetdeposition, corrosion and runoff process.</p>

<p>This licentiate study was initiated by copper, zinc and galvanized steel producers in Europe, who felt a need to assess runoff rates of copper and zinc from the pure metals and commercial products at marine exposure conditions. Their motive was the increasing concern in various European countries and the on-going risk assessments of copper and zinc within the European commission. Also the circumstance that available runoff rates so far, had been reported for mainly urban exposure conditions, rather than marine. A collaboration was therefore established with the French Corrosion Institute, which runs a marine test site in Brest, and a set of vital questions were formulated. Their answers are the essence of this licentiate study.</p><p>Based on the ISO corrosivity classification and one-year exposures, the marine atmosphere of Brest is fairly corrosive for zinc (class C3) and highly corrosive for copper (C4). Despite higher corrosivity classifications for both metals in Brest compared to the urban site of Stockholm, used as a reference site, nearly all runoff rates assessed for copper, zinc and their commercial products were lower in Brest compared to Stockholm. This was attributed to a higher surface wetting in Brest and concomitant higher removal rate of deposited chloride and sulphate species from the marine-exposed surfaces. The comparison shows that measured corrosion rates cannot be used to predict runoff rates, since different physicochemical processes govern corrosion and runoff respectively.</p><p>For copper, the runoff rate in Brest was approximately 1.1 g m^-2 yr^-1 with cuprite (Cu2O) as main patina constituent. During periods of very high chloride and sulphate deposition, paratacamite (Cu₂Cl(OH)₃) formed which increased the runoff rate to 1.5 g m^-2 yr^-1. For zinc, with hydrozincite (Zn₅(CO₃)2(OH)₆) as the main patina constituent, the runoff rate was relatively stable at 2.6 g m^-2 yr^-1 throughout the year, despite episodes of heavy chloride and sulphate deposition.</p><p>The application of organic coatings of varying thickness on artificially patinated copper or on different zinc-based products resulted in improved barrier properties and reduced runoff rates that seem highly dependent on thickness. The thickest organic coating (150 µm thick), applied on hot dipped galvanized steel, reduced the runoff rate by a factor of 100. No deterioration of organic coatings was observed during the one-year exposures. Alloying zinc-based products with aluminium resulted in surface areas enriched in aluminium and concomitant reduced zinc runoff rates.</p><p>The release rate and bioavailability of copper from different anti-fouling paints into artificial seawater was also investigated. It turned out that the release rate not only depends on the copper concentration in the paint, but also on paint matrix properties and other released metal constituents detected. Far from all copper was bioavailabe at the immediate release situation. In all, the results suggest the importance of assessing the ecotoxic response of anti-fouling paints not only by regarding the copper release, but rather through an integrated effect of all matrix constituents.</p>

Fundamental understanding of atmospheric corrosion mechanisms requires an in-depth understanding on the dynamic interaction between corrosive constituents and metal/alloy surfaces. This doctoral study comprises field and laboratory investigations that assess atmospheric corrosion and metal release processes for two different groups of alloys exposed in chloride-rich environments. These groups comprise two commercial Zn-Al alloy coatings on steel, Galfan™ (Zn5Al) and Galvalume™ (Zn55Al), and four copper-based alloys (Cu4Sn, Cu15Zn, Cu40Zn and Cu5Zn5Al). In-depth laboratory investigations were conducted to assess the role of chloride deposition and alloy microstructure on the initial corrosion mechanisms and subsequent corrosion product formation. Comparisons were made with long-term field exposures at unsheltered marine conditions in Brest, France. A multitude of surface sensitive and non-destructive analytical methods were adopted for detailed in-situ and ex-situ analysis to assess corrosion product evolution scenarios for the Zn-Al and the Cu-based alloys. Scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS) were employed for morphological investigations and scanning Kelvin probe force microscopy (SKPFM) for nobility distribution measurements and to gain microstructural information. SEM/EDS, infrared reflection-absorption spectroscopy (IRAS), confocal Raman micro-spectroscopy (CRM) and grazing incidence x-ray diffraction (GIXRD) were utilized to gain information on corrosion product formation and possibly their lateral distribution upon field and laboratory exposures. The multi-analytical approach enabled the exploration of the interplay between the microstructure and corrosion initiation and corrosion product evolution. A clear influence of the microstructure on the initial corrosion product formation was preferentially observed in the zinc-rich phase for both the Zn-Al and the Cu-Zn alloys, processes being triggered by microgalvanic effects. Similar corrosion products were identified upon laboratory exposures with chlorides for both the Zn-Al and the Cu-based alloys as observed after short and long term marine exposures at field conditions. For the Zn-Al alloys the sequence includes the initial formation of ZnO, ZnAl2O4 and/or Al2O3 and subsequent formation of Zn6Al2(OH)16CO3·4H2O, and Zn2Al(OH)6Cl·2H2O and/or Zn5(OH)8Cl2·H2O. The patina of Cu sheet consists of two main layers with Cu2O predominating in the inner layer and Cu2(OH)3Cl in the outer layer, and with a discontinuous presence of CuCl in-between. Additional patina constituents of the Cu-based alloys include SnO2, Zn5(OH)6(CO3)2, Zn6Al2(OH)16CO3·4H2O and Al2O3. General scenarios for the evolution of corrosion products are proposed as well as a corrosion product flaking mechanism for some of the Cu-based alloys upon exposure in chloride-rich atmospheres. The tendency for corrosion product flaking was considerably more pronounced on Cu sheet and Cu4Sn compared with Cu15Zn and Cu5Al5Zn. This difference is explained by the initial formation of zinc- and zinc-aluminum hydroxycarbonates Zn5(OH)6(CO3)2 and Zn6Al2(OH)16CO3·4H2O on Cu15Zn and Cu5Al5Zn, corrosion products that delay the formation of CuCl, a precursor of Cu2(OH)3Cl. As a result, the observed volume expansion during transformation of CuCl to Cu2(OH)3Cl, and the concomitant flaking process of corrosion products, was less severe on Cu15Zn and Cu5Al5Zn compared with Cu and Cu4Sn in chloride-rich environments. The results confirm the barrier effect of poorly soluble zinc and zinc-aluminum hydroxycarbonates Zn5(OH)6(CO3)2 and Zn6Al2(OH)16CO3·4H2O, which results in a reduced interaction between chlorides and surfaces of Cu-based alloys, and thereby reduced formation rates of easily flaked off corrosion products. From this process also follows reduced metal release rates from the Zn-Al alloys. / Bättre molekylär förståelse för metallers atmosfäriska korrosion kräver en fördjupad kunskap i det dynamiska samspelet mellan atmosfärens korrosiva beståndsdelar och metallytan. Denna doktorsavhandling omfattar laboratorie- och fältundersökningar av korrosions- och metallfrigöringsprocesser av två grupper av legeringar som exponerats i kloridrika atmosfärsmiljöer: två kommersiella Zn-Al beläggningar på stål, Galfan™ (Zn med 5% Al, förkortat Zn5Al) och Galvalume™ (Zn55Al), samt fyra kopparbaserade legeringar (Cu4Sn, Cu15Zn, Cu40Zn och Cu5Zn5Al). Undersökningar har genomförts i renodlade laboratorie-miljöer med för-deponerade NaCl-partiklar i en atmosfär av varierande relativ fuktighet. Syftet har varit att utvärdera betydelsen av kloriders deposition och legeringarnas mikrostruktur på korrosionsmekanismen samt bildandet av korrosionsprodukter. Jämförelser av korrosionsmekanismer har även gjorts efter flerårsexponeringar av samma legeringar i en marin fältmiljö i Brest, Frankrike. Undersökningarna har baserats på ett brett spektrum av analysmetoder för detaljerade studier dels under pågående atmosfärisk korrosion (in-situ), och dels efter avslutad korrosion (ex-situ). Legeringarnas mikrostruktur och tillhörande variation i ädelhet hos olika faser har undersökts med svepelektronmikroskopi och energidispersiv röntgenmikroanalys (SEM/EDS) samt med en variant av atomkraftsmikroskopi (engelska: scanning Kelvin probe force microscopy, SKPFM). Korrosionsprodukternas tillväxt har analyserats in-situ med infraröd reflektions-absorptionsspektroskopi (IRAS), samt morfologi och sammansättning av bildade korrosionsprodukter ex-situ med SEM/EDS, konfokal Raman mikro-spektroskopi (CRM) samt röntgendiffraktion vid strykande ifall (GIXRD). Det multi-analytiska tillvägagångssättet har medfört att det komplexa samspelet mellan de skilda legeringarnas mikrostruktur, korrosionsinitiering och bildandet av korrosionsprodukter kunnat studeras i detalj. En tydlig påverkan av mikrostruktur på det initiala korrosionsförloppet har kunnat påvisas. Korrosionsinitieringen sker företrädesvis i mer zinkrika faser för såväl Zn-Al- som Cu-Zn-legeringar och orsakas av mikro-galvaniska effekter mellan de mer zinkrika, mindre ädla, faserna och omgivande faser. Deponerade NaCl-partiklar påskyndar den lokala korrosionen oberoende av mikrostruktur. Snarlika sekvenser av korrosionsprodukter har kunnat påvisas såväl efter laboratorie- som fältexponeringar. För Zn-Al-legeringar bildas först ZnO, ZnAl2O4 och/eller Al2O3, därefter Zn6Al2(OH)16CO3·4H2O och Zn2Al(OH)6Cl·2H2O och/eller Zn5(OH)8Cl2·H2O. På ren koppar bildas ett inre skikt dominerat av Cu2O, ett mellanskikt av CuCl och ett yttre skikt med i huvudsak Cu2(OH)3Cl. Beroende på legeringstillsats har även SnO2 och Zn5(OH)6(CO3)2 kunnat identifieras. En mekanism för flagning av korrosionsprodukter på kopparbaserade legeringar i kloridrika atmosfärer har utvecklats. Tendensen för flagning har visat sig vara mycket mer uttalad på ren Cu och Cu4Sn än på Cu15Zn och Cu5Al5Zn. Skillnaden kan förklaras med hjälp av det tidiga bildandet av Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O på Cu15Zn och Cu5Al5Zn som fördröjer bildandet av CuCl, en föregångare till Cu2(OH)3Cl. Därigenom hämmas även den observerade volymexpansionen som sker när CuCl omvandlas till Cu2(OH)3Cl, en process som visar sig vara den egentliga orsaken till att korrosionsprodukterna flagar. Resultaten bekräftar barriäreffekten hos de mer svårlösliga faserna Zn5(OH)6(CO3)2 och Zn6Al2(OH)16CO3·4H2O, vilken dels resulterar i en minskad växelverkan mellan klorider och de legeringsytor där dessa faser kan bildas, och dels i en reducerad metallfrigöringshastighet. / <p>QC 20140915</p> / Autocorr, RFSR-CT-2009-00015 Corrosion of heterogeneous metal-metal assemblies in the automotive industry / Atmospheric corrosion and environmental metal dispersion from outdoor construction materials