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Dealloying is widely utilized but is a dangerous corrosion process as well. Here we report an atomistic picture of the initial stages of electrochemical dealloying of the model system Cu(3)Au (111). We illuminate the structural and chemical changes during the early stages of dissolution up to the critical potential, using a unique combination of advanced surface-analytical tools. Scanning tunneling microscopy images indicate an interlayer exchange of topmost surface atoms during initial dealloying, while scanning Auger-electron microscopy data clearly reveal that the surface is fully covered by a continuous Au-rich layer at an early stage. Initiating below this first layer a transformation from stacking-reversed toward substrate-oriented Au surface structures is observed close to the critical potential. We further use the observed structural transitions as a reference process to evaluate the mechanistic changes induced by a thiol-based model-inhibition layer applied to suppress surface diffusion. The initial ultrathin Au layer is stabilized with the intermediate island morphology completely suppressed, along an anodic shift of the breakdown potential. Thiol-modification induces a peculiar surface microstructure in the form of microcracks exhibiting a nanoporous core. On the basis of the presented atomic-scale observations, an interlayer exchange mechanism next to pure surface diffusion becomes obvious which may be controlling the layer thickness and its later change in orientation.

The integration of a scanning Kelvin probe (SKP) and a scanning electrochemical microscope (SECM) into a single SKP-SECM setup, the concept of the proposed system, its technical realization, and first applications are presented and discussed in detail. A preloaded piezo actuator placed in a grounded stainless steel case was used as the driving mechanism for oscillation of a Pt disk electrode as conventionally used in SECM when the system was operated in the SKP mode. Thus, the same tip is recording the contact potential difference (CPD) during SKP scanning and is used as a working electrode for SECM imaging in the redox-competition mode (RC-SECM). The detection of the local CPD is established by amplification of the displacement current at an ultralow noise operational amplifier and its compensation by application of a variable backing potential (V(b)) in the external circuit. The control of the tip-to-sample distance is performed by applying an additional alternating voltage with a much lower frequency than the oscillation frequency of the Kelvin probe. The main advantage of the SKP-SECM system is that it allows constant distance measurements of the CPD in air under ambient conditions and in the redox-competition mode of the SECM in the electrolyte of choice over the same sample area without replacement of the sample or exchange of the working electrode. The performance of the system was evaluated using a test sample made by sputtering thin Pt and W films on an oxidized silicon wafer. The obtained values of the CPD correlate well with known data, and the electrochemical activity for oxygen reduction is as expected higher over Pt than W.

The corrosion of rusted iron coated by organic lacquers is analysed. The rates of metal dissolution and oxide reduction are measured by in situ Moβbauer spectroscopy, the rate of oxygen reduction by a gas volumetric type of technique. For the first 100 h after wetting, rust reduction is more important than oxygen reduction as the cathodic partial reaction. Due to rust reduction, the morphology of the oxide scale is changed, which results in a loss of adhesion between the polymer and the substrate. The stability of the rust layer can be increased significantly after suitable surface treatments. Most effective is the chemisorption of organophosphates on to the surface of γ-FeOOH. After this treatment rust reduction is nearly completely inhibited and no loss of adhesion is observed after exposure of the modified and polymer coated material to aerated electrolytes.

Stress corrosion cracking (SCC) behavior of two high nitrogen steels, P900 (0.58 wt% N) and P900N (0.90 wt% N), in 1 wt% NaCl solution under an applied potential condition was investigated by slow strain rate testing (SSRT). The experimental results showed that there exists a critical potential for SCC for each of these two materials in the above solution. At applied potentials of 500 and 650 mV(SHE), SCC assisted by pitting corrosion was found to occur in P900 and P900N, respectively. The results also indicated that P900N is more resistant than P900 to SCC in 1 wt% NaCl solution. Electrolyte analyses after SSRT tests showed that during SCC tests most nitrogen from the steels is converted to NH 4 + .

Several new techniques have recently been introduced in order to analyse the corrosion of metals covered by very thin or even adsorbed electrolyte layers. In this study the same techniques are used for the first time to investigate the inhibition mechanism of a typical vapour phase inhibitor (ammonium benzoate) on iron under atmospheric corrosion conditions. During wet/dry transitions the corrosion potential and the corrosion rate are measured without touching the surface under investigation, the kinetics of the metal dissolution and the oxygen reduction are analysed in bulk electrolytes as well as below very thin electrolyte layers and the corrosion rate and the chemical composition of the inhibitor covered surface are determined under non-condensing reaction conditions, where the surface is covered by monolayers of water only. It is shown that the rate of the anodic and the cathodic partial reactions of the corrosion process are strongly effected by the thickness of the electrolyte layer. Due to the presence of the inhibitor the surface is passivated, but stable passivity is observed only for very thin electrolyte layers. The inhibitor efficiency, therefore, cannot be deduced from conventional electrochemical experiments in bulk electrolytes, but only from studies on a metal surface which is covered either by very thin layers or even adsorbed electrolyte layers.

The mechanism by which an alloy corrodes into a potentially useful porous sponge is understood qualitatively, but quantitative predictions of its final structure have been lacking. A model for this has now been proposed.

The corrosion mechanism of copper at 373 and 300 K in the presence of submicron (NH[sub 4])[sub 2]SO[sub 4] particle deposits has been investigated. Several in situ techniques have been used to monitor the corrosion process in real time. At and above the critical relative humidity of (NH[sub 4])[sub 2]SO[sub 4], dissolution of Cu is followed by formation of Cu[sub 2]O, oxidation of Cu(I) ions to Cu(II) ions, and precipitation of antlerite [Cu[sub 3](SO[sub 4])(OH)[sub 4]], brochantite [Cu[sub 4](SO[sub 4])(OH)[sub 6]], or posnjakite [Cu[sub 4](SO[sub 4])(OH)[sub 6][center dot]H[sub 2]O]. The amount of corrosion product formed increases with amount of (NH[sub 4])[sub 2]SO[sub 4] particles, relative humidity (RH), and temperature. The in situ techniques allowed the authors to confirm and refine the individual steps in the multistep mechanism proposed in earlier work.

The atmospheric corrosion of zinc in the presence of (NH{sub 4}){sub 2}SO{sub 4} particles has been investigated at 300 and 373 K in air-water vapor mixtures. The development of corrosion products was followed by several in situ techniques, including Fourier transform infrared-spectroscopy, X-ray diffraction, pH measurements, and scanning Kelvin probe measurements. Unlike earlier work on copper and aluminum, zinc reacts with the particles below the critical relative humidity (CRH) of (NH{sub 4}){sub 2}SO{sub 4}. At 300 K reaction was observed at 65% relative humidity (RH), but not at 60% /RH. This is attributed to the presence of basic zinc carbonate on the surface, which absorbs sufficient water at this low RH to make electrochemical reactions possible. At and above the CRH of (NH{sub 4}){sub 2}SO{sub 4}, zinc reacts with (NH{sub 4}){sub 2}SO{sub 4} forming mixed ammonium zinc sulfate and later on basic zinc sulfate, and at 373 K additionally zincite (ZnO). Above the CRH of (NH{sub 4}){sub 2}SO{sub 4}, the corrosion potential decreases directly after formation of droplets surrounding the particles and zinc becomes active. Corrosion mechanisms are proposed to explain the observations.

A new technique is presented, which is able to detect corroding parts of a metal surface below technical polymercoatings. The technique (vibrating reference electrode) is based on the observation, that the local corrosion potential – which in turn is given by the rates of the anodic and cathodic partial reactions of the corrosion process– is quite different for an intact and for a delaminated metal/polymer interface. In this paper two different coatings are analysed, which are used in technical flue gas desulfurisation (FGD) plants. It is shown, that the different stability of the two coatings can clearly be elucidated by mapping the corrosion potential of the surface in a humid atmosphere. Uberwachung der Blasenbildung bei organischen Beschichtungen durch kontaktlose Messung Es wird eine neue Technik vorgestellt, die in der Lage ist, korrodierende Stellen unterhalb technischer Polymerbeschichtungen nachzuweisen. Das Verfahren (vibrierende Referenzelektrode) basiert auf der lokalen Messung von Korrosionspotentialen, die ihrerseits durch die Kinetik der anodischen und kathodischen Teilreaktion der Korrosion gegeben sind. Die Korrosionspotentiale intakter Metall/Polymer-Grenzflachen unterscheiden sich deutlich von solchen Potentialen, die an delaminierten Metall-Polymer-Verbunden gemessen werden. In dieser Arbeit werden zwei technische Beschichtungen untersucht, die auch in Rauchgasentschwefelungsanlagen eingesetzt werden. Es wird gezeigt, das die unterschiedliche Stabilitat der Beschichtung durch die Abbildung von Korrosionspotentialen in einer feuchten Atmosphare deutlich herausgearbeitet werden kann.

Monomolecular LB films of n-octadecyltrichlorosilane (n-OTS) and chlorodimethyloctadecylsilane (CODS) have been produced on metal substrates like Fe and Ni in order to protect the reactive metal surface against corrosive species like H2O, O2 and SO2. To characterize defects within the monomolecular LB films, they were studied by UHV methods such as scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and scanning Auger microscopy (SAM). In dry or humid air atmospheres it is possible to measure a work function topography of the LB film covered materials with a scanning Kelvin microprobe. In dry air the work function topography corresponds to the distribution of dipole potentials. Therefore it is possible to analyze intrinsic defects within the monomolecular LB film on the metal surface. In a humid atmosphere the work function is mainly given by the local corrosion potential of the metal substrate and therefore delamination processes of the monomolecular film can be studied as well as the stability of the LB film coated metal substrate.

In order to increase the chemical and electrochemical stability of metal/polymer composite materials the first monolayer of the organic coating should be bonded by chemical bonds to the substrate. In this study, the bond formation between iron and n-decanethiol has been studied by surface sensitive techniques (XPS, AES) and the stability of the modified surface by cyclic voltammetry in different aqueous electrolytes. Chemisorptive bonds between the substrate and the thiol could be formed probably by cleavage of the S-H bond -only, if the metal surface is free of any oxide layer. Cyclovoltammetry in nitrogen purged acqueous electrolytes enhances the package density of the adsorbed molecules and leads to a more perpendicular orientation of the thiol molecules with respect to the substrate surface. The very stable bond between iron and the thiol supresses an oxidation of both the iron surface and the SH group in air and in electrolytes of different pH within a large potential range.

It is possible to measure the work-function of polymer coated materials with a Kelvin-probe. In a humid atmosphere this work-function is mainly given by the corrosion-potential of the metal substrate. The use of a scanning Kelvinprobe then allows to map the corrosion potential of polymer coated material with a local resolution of approx. 20 μm and to follow the delamination of polymer coatings as well in the vicinity of defects as on metal substrates, which are contaminated at the metal/polymer interface. Simultaneously, the diffusion of oxygen can be followed with a high local resolution after a jump of the oxygen activity within the gas phase.—The same techniques are used to analyse intrinsic defects within monomolecular LB-films. In a dry gas phase the Volta potential map corresponds to the distribution of dipole-potentials and therefore allows to distinguish between covered and uncovered parts of the substrate, as the ordered LB-film shows rather large dipole-potentials. In a humid atmosphere the Volta potential map again is dominated by the corrosion potential of the substrate and therefore the delamination of the LB-film in the vicinity of defects can be studied as well as the stability of the film on the metal substrate far away from any defect.

Die auf Fe-Basislegierungen gebildeten Rostschichten sind elektronisch sehr reaktiv. Durch Polarisation dieser Oxidschichten werden Festkorperreaktionen ermoglicht, die zur Reduktion der 3-wertigen Oxidhydrate fuhren. Diese Redox-Reaktionen erlauben eine Eisenauflosung ohne Reduktion von Sauerstoff und erhohen damit den Metallabtrag insbesonders bei periodisch variierenden Korrosionsbedingungen und bei polymerbeschichteten Werkstoffoberflachen. Durch die Oxidreduktion werden elektronenleitende Oxide gebildet, die die Kinetik von Sauerstoffreduktion bestimmen. Schlieslich andert sich bei der Reduktion der Rostschicht die Rostmorphologie. Dies fuhrt zu einem Haftungsverlust bei polymerbeschichteten oxidbelegten Metalloberflachen. Influence of rust layers on corrosion reactions of low alloy steels Rust layers formed on iron base alloys are electrochemically highly reactive. Due to a polarisation of these oxide scales solid state reactions are induced, by which the 3-valent iron oxides are reduced. These redox reactions allow the dissolution of iron without the reduction of oxygen and therefore increase the corrosion rate, if the corrosion conditions vary periodically or if the material is coated by a polymer layer. Due to the oxide reduction electron-conducting oxides are formed, which determine the rate of the oxygen reduction. This causes the loss of adhesion for polymer coated and oxide covered iron substrates.

Die Kinetik der Korrosion von polymerbeschichtetem Reineisen in 0,1 M NaCl wurde untersucht. Durch die Praparation von Proben mit einer unter der Beschichtung positionierten Referenzelektrode konnte eine direkte Polarisation der Phasengrenze Metall/Polymer bei Gleich- und Wechselspannungsmessungen erreicht werden. Die Kombination dieser Messung mit den Ergebnissen nicht elektrochemischer Techniken, wie z.B. Kelvin-Sonde, Mosbauerspektroskopie und O2-Verbrauchsmessungen, liefert neue Erkenntnisse zur Korrosionskinetik unter einer Polymerbeschichtung. Die Metalloberflache ist von einem gequollenen Polymerfilm bedeckt, und bei der Korrosion werden primar im Polymer geloste Eisenkationen gebildet. Dies fuhrt zu einer extremen Hemmung der anodischen Metallauflosung (Tafelneigungen mehrere 100 mV). Auch die kathodische Teilreaktion (O2-Reduktion) lauft nicht unter transportkontrollierten Bedingungen, sondern aufgrund ihrer gehemmten Kinetik durchtrittskontrolliert ab. Die Diffusionskoeffizienten von Wasser und Sauerstoff in einer haftenden Beschichtung wurden bestimmt. New model of corrosion protection of organic coatings on iron The corrosion kinetics of polymer-coated iron is investigated in 0.1 M NaCl. As special samples are prepared with the reference electrode located at the metal/polymer interface a direct polarization of this interface is possible by AC and DC techniques. A combination of these measurements with results obtained by non-electrochemical techniques like Kelvin-probe, Mosbauerspectroscopy and O2-consumption allows to derive a new model of the corrosion kinetics below a polymer coating. The metal surface is covered by a swollen polymer layer and during corrosion at first iron cations are dissolved in the organic matrix. This results in a strong inhibition of the anodic partial reaction (Tafel-slope several 100 mV). Also the cathodic partial reaction (O2-reduction) is not transport-limited but its rate is given by the electron transfer reaction. The diffusion of water and oxygen is investigated on adherent polymer films.

A new technique is presented, which is able to detect directly the corrosion induced delamination of polymer coatings from metallic substances. The technique is based on a local measurement of Volta-potentials. The defamination in the vicinity of local defects and the delamination caused by local contaminations below intact polymer layers can be determined quantitatively.

The principle of operation and the design of a scanning Kelvin microprobe for the determination of corrosion potential profiles are described. The profiles of Volta potentials on galvanically coupled metals under humidity films were determined and are compared to profiles for the same metals under dry nitrogen. The relation between the Volta potential and the corrosion potential and some of the difficulties involved in studying corrosion under humidity films are discussed

In dieser Arbeit werden neue Wege vorgeschlagen, organische Polymere auf Metalloberflachen uber chemische Hauptvalenzbindungen zu verankern. Zwischen Polymer und Metall sollen bifunktionelle organische Molekule angeordnet werden, die uber chemische Bindungen mit reaktiven Zentren der Metalloberflache und uber konventionelle (C-C)-Bindungen mit dem Polymer verknupft sind. Als einen ersten Schritt in dieser Richtung wird die Anbindung von einfachen aliphatischen Mercaptanen an Eisenoberflachen untersucht. Oberflachenanalytische Experimente zeigen, das Mercaptane an metallisch blanken Eisenoberflachen unter Ausbildung von (Fe-S-R)-Bindungen anbinden. Die Reaktion selbst mus unter elektrochemisch kontrollierten Bedingungen durchgefuhrt werden. Die Stabilitat der Bindung ist sehr gros sowohl in Luft als auch in zahlreichen Elektrolyten. Sie wird begrenzt durch eine massive Sauerstoffreduktion, bei der die chemisorbierten Mercaptanmolekule wahrscheinlich durch das bei der Sauerstoffreduktion gebildete H2O2 chemisch aufoxidiert werden und anschliesend desorbieren. Binding behaviour of organic monomers on iron surfaces and corrosion of the resultant chemically modified surfaces In this study a new concept is discussed, to anchor polymers onto metal surfaces by primary chemical bonds. Organic molecules with two functional groups are positioned between polymer and substrate, which should be bonded to reactive centers of the metal surface by one functional group and to the polymer by conventional C-C bonds. As a first in this direction, the reaction between simple aliphatic mercaptanes and iron surfaces has been studied in detail. Surface analytical investigations have proven, that mercaptane molecules can be bonded to metallic clean iron surfaces by Fe-S-R bonds. The reaction itself has to be performed under well controlled electro-chemical conditions. The stability of the bonds is quite large as well in air as in many different electrolytes. The stability is limited by a prolonged oxygen reduction at large cathodic overpotentials. Probably, the mercaptane molecules are chemically oxidised by the H2O2 formed during the reduction of oxygen and the resulting sulfonic acid desorbs from the electrode surface.

Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces. Refereed/Peer-reviewed

Reactive wetting plays a crucial role in many technical processes, from soldering in microelectronics, production of metal/ceramic composites, to hot dip galvanizing in mass production of zinc coated steel sheet. In all these cases the wetting behavior of metal melts on different surfaces plays a crucial role in material joining and coating. In all these processes the formation of the interfacial reaction layer has to occur within as short a time as possible in order to ensure a fast overall production speed. As the interfacial layer determines the stability of the formed composites, detailed knowledge of its growth mechanisms is required for a directed process optimization. However, the investigation of the processes occurring at the buried interface between substrate and wetting phase is difficult, especially for the case of liquid metal wetting metallic or ceramic solid substrates at high temperatures. Here, a novel advanced technique for the investigation of high temperature wetting processes up to a temperature of 1100 K is presented. It is based on the sessile drop technique but, in addition, allows spinning off the droplet at any chosen wetting time, thus providing direct access to the interfacial reaction layer. Since the experimental setup is integrated into a UHV compatible reaction chamber, not only excellent control of the composition of the atmosphere is ensured, but also direct transfer to surface analytical tools such as scanning electron microscope or electron spectroscopy for chemical analysis without intermediate exposure to air is realized. As will be shown for the case of hot dip galvanising of steel, this is an outstanding advance compared to existing methods.

For a better understanding of the initiation of localised corrosion, there is a need for analytical tools that are capable of imaging corrosion pits and precursor sites with high spatial resolution and sensitivity. The lateral electrochemical contrast in alternating-current scanning electrochemical microscopy (AC-SECM) has been found to be highly dependent on the frequency of the applied alternating voltage. In order to be able to obtain data with optimum contrast and high resolution, the AC frequency is swept in a full spectrum at each point in space instead of performing spatially resolved measurements at one fixed perturbation frequency. In doing so, four-dimensional data sets are acquired (4D AC-SECM). Here, we describe the instrument set-up and modus operandi, along with the first results from the imaging of corroding surfaces. Corrosion precursor sites and local defects in protective organic coatings, as well as an actively corroding pit on 304 stainless steel, have been successfully visualised. Since the lateral electrochemical contrast in these images varies with the perturbation frequency, the proposed approach constitutes an indispensable tool for obtaining optimum electrochemical contrast. Um die Entstehung lokaler Korrosionsphanomene untersuchen zu konnen, bedarf es ortsauflosender Methoden, die beispielsweise Lochfras oder Korrosionsvorstufen mit hoher lateraler Auflosung visualisieren konnen. Bei der Abbildung lokaler elektrochemischer Aktivitat mittels wechselstrombasierter elektrochemischer Rastermikroskopie (AC-SECM) ist der Kontrast in hohem Mase abhangig von der gewahlten Anregungsfrequenz. Um den Informationsgehalt der erhaltenen Bilder zu erhohen und optimalen elektrochemischen Kontrast zu erzielen, wird vorgeschlagen, an jedem Punkt des Rastergitters, ein komplettes Frequenzspektrum aufzunehmen, anstatt die Oberflache mit einer einzigen, willkurlich gewahlten Anregungsfrequenz abzurastern. Dadurch werden vierdimensionale Datensatze erhalten (4D AC-SECM). Wir berichten hier uber den Aufbau des neu entwickelte Instrumentes, seine Funktionsweise und uber erste Ergebnisse zur Abbildung korrodierender Oberflachen. Korrosionsvorstufen und Defekte in organischen Schutzschichten konnten ebenso erfolgreich visualisiert werden wie ein Korrosionsherd auf einer 304 Edelstahl-Oberflache. Die hier vorgestellte Herangehensweise garantiert die Erfassung des optimalen elektrochemischen Kontrastes und damit eine hohe Auflosung bei der Visualisierung korrodierender Oberflachen.

Monomolecular Langmuir-Blodgett films of silanes have been prepared on water by using a computer-controlled Langmuir balance. The LB films were transferred from the fluid to solid substrates like Fe, Cr and Ni/Cr alloy. By using scanning electron microscopy (SEM) and scanning Auger microscopy (SAM) it was shown that both methods allowed very easy identification of covered and uncovered areas of the solid substrate. Most probably a separation of the LB film occurs during transfer from the fluid to the solid substrate leading to the observed island structure of the LB films on the solids.

In order to develop new composite materials between reactive metals and polymers, it is proposed to place organic monomers at the metal/polymer phase boundary, which can be coupled by covalent/ionic bonds to reactive centres of the metal substrate and later by covalent bonds to the polymer itself. As a first step, the model system iron/n-decanethiol (n-decylmercaptan, C10H21SH) has been investigated by AES and XPS. It is shown that the mercaptan binds to metallic clean iron surfaces through the sulphur atom, probably by cleavage of the SH bond. The S 2p3/2 peak has a binding energy of 162.4 ± 0.2 eV. Anodic polarization and ageing in the laboratory atmosphere do not oxidize these chemisorbed molecules; the oxidation reactions of the substrate are suppressed too. After cyclovoltammetry (−1.0 VSHE⩽ U ⩽ + 0.6 VSHE), better oriented chemisorbed molecules are packed more densely on top of the surface.

This promising method of chemically modifying reactive metal surfaces with organic molecules prior to the attachment of polymers could have a significant impact on work aimed at the optimization of the performance of composite materials. Strong chemical bonds can be formed between a suitably prepared metal surface and certain monomers, which resist even an electrochemical polarization of the interface at large cathodic or anodic overpotentials. These chemical bonds can, however, only be achieved if a suitable structure and reactivity is generated, for example, by using electrochemical techniques. Therefore, further technological progress in this important area requires the cooperation of scientists from rather different scientific disciplines like electrochemistry, surface science and organic chemistry, in order to optimize the structure of the organic monomers and to provide the best possible bonds to the different metals in use, taking into account the rather different reactivity of technologically important media.

In this series of three papers new techniques are described, which allow the investigation of the corrosion kinetics of metal surfaces which are covered by very thin or even adsorbed electrolyte layers. In this first part the experimental arrangement is discussed in detail, which is used to measure simultaneously corrosion rates and corrosion potentials of atmospherically corroding iron surfaces during several wet/dry transitions without touching the surface under investigation. The theoretical basis for the measurement of electrode potentials using a Kelvin probe as a reference electrode is evaluated. Additional experiments have been performed to check the validity of the measured Volta potential and its correlation to the corrosion potential of the metal/electrolyte interface. The results prove that the potential drop across the oxide scale formed on top of the iron surface is small if the surface is kept in a humid environment (e.g. 95% relative humidity). Then, the Volta potential difference between surface and Kelvin probe can be directly correlated to the corrosion potential of the corroding metal surface.

In this study for the first time a circuit is presented which allows the measurement of polarisation curves on metal surfaces which are covered by electrolyte layers as thin as 2 μm. The circuit does not need any Luggin capillary but uses a Kelvin probe as a reference electrode which does not touch the surface under investigation. Results are discussed which have been obtained with platinum and iron as working electrodes. On iron electrodes, during drying the rate of the oxygen reduction is accelerated due to a faster transport of oxygen through the thin electrolyte layer. The surface is passivated either due to the precipitation of corrosion products or due to pH-changes inside the thin electrolyte layer. This confirms the model of the atmospheric corrosion of iron and steel presented in part 2 of this paper.

We show numerically and experimentally the existence of bound states of bright and dark temporal solitons. These 'soliton molecules' exist only in dispersion-managed fiber.

Corrosion of iron presents a serious economic problem. Whereas aerobic corrosion is a chemical process, anaerobic corrosion is frequently linked to the activity of sulphate-reducing bacteria (SRB). SRB are supposed to act upon iron primarily by produced hydrogen sulphide as a corrosive agent and by consumption of 'cathodic hydrogen' formed on iron in contact with water. Among SRB, Desulfovibrio species--with their capacity to consume hydrogen effectively--are conventionally regarded as the main culprits of anaerobic corrosion; however, the underlying mechanisms are complex and insufficiently understood. Here we describe novel marine, corrosive types of SRB obtained via an isolation approach with metallic iron as the only electron donor. In particular, a Desulfobacterium-like isolate reduced sulphate with metallic iron much faster than conventional hydrogen-scavenging Desulfovibrio species, suggesting that the novel surface-attached cell type obtained electrons from metallic iron in a more direct manner than via free hydrogen. Similarly, a newly isolated Methanobacterium-like archaeon produced methane with iron faster than do known hydrogen-using methanogens, again suggesting a more direct access to electrons from iron than via hydrogen consumption.

Forming of pre-coated metal sheet becomes of increasing importance in various fields of industrial application. For instance, the trend in automotive industry goes for ready coated steel sheet that can be formed and cut without loss of performance. This so called “finish first, fabricate later” concept increases the value of the steel sheet supplied by the steel industry and releases the automotive industry from the burden of the coating process. Consequently, studies on the effect of forming on the performance of corrosion protective coating systems adhering to metals sheet are carried out in order to determine the forming limiting curves for existing coatings [1]. New coating systems are sought in order to improve the formability of coating/metal sheet composites. As a very promising step into this direction, in the recent years ultra-thin plasma-polymer films have emerged as candidates for substituting phosphatation and the environmentally critical chromatation as pre-treatments for steel sheet. These Si-containing plasma polymers provide good corrosion protection properties to steel as well as to zinc-coated steel [2–3].

A Langmuir-Blodgett-Film-Balance was modified, in order to obtain electrochemical potential control of metal substrates during film deposition. With this balance octadecylmercaptan (ODM) was brought onto gold substrates under different potentials. The mercaptan monolayer was investigated by means of surface analytical techniques (XPS, ARXPS). Initial results concerning the potential dependence of the LB-layer are presented.

The adsorption of methyl and butyl-trimethoxysilane onto iron surfaces from the gas phase at different humidity levels has been investigated in situ with a quartzcrystal micro-balance and with ATR-IR spectroscopy. The thickness of the resulting siloxan polymer depends on the humidity during the film preparation. The polymer coating inhibits the corrosion of iron in an SO2-containing atmosphere.

The 83 institutes and research facilities of the Max Planck Society, established in 1948, include some of the world's leading scholars in the life sciences, including 17 Noble Prize winners, and publish 15,000 research papers annually. For the past 18 years, biologists have stood at the helm of the prestigious German organization. But last month, an electrochemist and materials scientist, Martin Stratmann, began a six-year term as president of the Munich-based society.Stratmann, who is 60, served as the director of the Max Planck Institute for Iron Research in Dusseldorf since 2000, where he helped develop self-healing coatings that can protect steels and other metals from rust. Stratmann spoke with David Levine about his vision for the Max Planck Society and about what the change of guard will mean for biomedical research. The conversation has been edited for clarity.

Cu-nanoclusters can be produced in an electrochemical environment by tip-induced metal deposition using an electrochemical scanning tunneling microscope (EC-STM). These clusters, consisting of 100-1000 atoms only, show a surprising stability against anodic oxidation. The clusters, which are 2-3 atomic layers in height dissolve slowly when the applied potential is increased step by step to 200 mV positive of the reversible Nernst potential for “normal” copper dissolution. The presented work gives evidence that the unusual stability of the clusters could be a consequence of interfacial alloying between the cluster and the underlying substrate. In order to study these effects Cu-nanoclusters have been produced on pure gold substrates and on carefully prepared Au3Cu(111)-substrates. This work compares the results obtained on both substrates.

New challenges on the R & D side result from the ever increasing demands made on the "performance "of surface treated sheets by the manufacturing companies and the customers. Corrosion protection must be improved decisively, especially in view of the fact that the sheets used, for instance, in automotive engineering are becoming thinner more and more. For reasons of processing, environment protection and saving of resources, this cannot be achieved by just increasing the thickness of conventional coating systems. Moreover, additonal functions of the surface coating systems are increasingly in demand like, e. g., scratch resistance, antifingerprint and antidirt characteristics. This clearly shows that the conventional surface treatment processes more and more are reaching boundaries in respect of their capability of further development. A distinct progress is achievable only by the application of novel coating materials, many of which can only be applied with processes of PVD or CVD) or radiation/beam technology, i. e., processes which have been applied hardly or not at all in steel strip surface treatment up to date.

The reduction of oxygen has been studied on octadecylmercaptan self-assembled monolayers adsorbed on gold substrates in borate buffer solutions with a rotating disc electrode. A great inhibition of the oxygen reduction and other electrochemical reactions by these monolayers has been found. However, after polarisation at −0.80 V she the protecting properties of the film against electron transfer reactions are lost, and a behaviour similar to bare gold is observed. Ex situ XPS indicates that the thiol monolayer has not been desorbed to a large extent during oxygen reduction. Disorders of the monolayer structure and desorption of thiol molecules are proposed as the main reasons for the accessibility of electrochemical reactions to the surface.

The applicability of a new experimental technique - the Scanning Kelvinprobe - for the analysis of the delamination of polymer films from galvanized steel is discussed. Defect ions having direct access to the zinc/ polymer interface will diffuse along this interface, a process, which can be monitored by the Kelvinprobe in a very early state with a high local resolution. After incorporation of ions a galvanic element is formed, the local cathode being at the delamination front, where oxygen is reduced, and the local anode at the zinc coated defect. For the model polymer under investigation the interaction between the film and the substrate is weak and the rate determining step for the delamination is the diffusion of cations from the local anode to the local cathode. An exposure to a highly CO(2)-containing atmosphere before the delamination prolongs the incubation time of delamination. If there is no zinc layer at the defect, an anodic delamination mechanism occurs. Zinc is dissolved under the polymer film, while the steel surface is cathodically protected.

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Combinatorial material development was combined with high throughput microelectrochemistry to allow an efficient but comprehensive investigation of the interface chemistry of Al rich Al–Fe alloys as a function of their chemical composition. Composition spread thin films with a linear composition gradient were produced by thermal codeposition. A scanning droplet cell was used to determine the open circuit potential and to perform successive anodic oxide formation with intermittent impedance spectroscopy. The film formation factor, the relative permittivity of the oxides and the onset potential of oxide formation were determined quantitatively as function of the composition with a resolution of 0.5 at.%. An unexpected synergistic effect is found in a very narrow composition range between 9 and 12 at.% Fe. This effect, which shifts the onset potential by nearly 1 V, is discussed in terms of a local accumulation of Fe resulting in a redox stabilisation of space charge layer formation during high-field oxide growth. The results are supported by composition and depth dependent XPS measurements.