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In the Belgian supercontainer concept, a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research has...

The materials corrosion test (MaCoTe) is a long‐term, multinational in situ corrosion experiment setup at the Grimsel Test Site, Switzerland. The experiment has been operating since 2014 with a focus on the corrosion behaviour of container materials for the disposal of high‐level waste and spent nuclear fuel under conditions representing a granitic deep geological repository. The experiment consists of eight modules containing metal coupons and bentonite. Two of the modules, each with a different bentonite density, have been retrieved after 394 days of exposure and have been analysed using a range of techniques aimed at studying the corrosion behaviour of the metals and the mineralogical evolution of the bentonite. Weight loss measurements show that carbon steel had a relatively low average corrosion rate (~2 µm year−1). Much lower average corrosion rates were measured for the various types of copper (0.13–0.32 µm year−1). No detectable corrosion was measured on stainless steel coupons. To date, no significant differences were observed in the corrosion behaviour and rate of the test metals in bentonite with different dry densities.

Since 2012, a long‐term in situ corrosion experiment (IC‐A) is being conducted in the Mont Terri Underground Research Laboratory in Switzerland to investigate the corrosion behaviour of candidate canister materials in conditions representative of the Swiss concept for the disposal of high‐level waste and spent nuclear fuel. To date, carbon steel and various types of copper coatings have been retrieved after different exposure periods of up to 3 years, and characterised to establish the composition of the corrosion product, the morphology of the corroded surface, the nature of the interaction between the metal and the surrounding bentonite, and the microbial populations in the bentonite and surrounding porewater. For carbon steel specimens, a complex corrosion product was identified, consisting predominantly of magnetite. Much less alteration on either the metal or the bentonite was observed in the case of copper samples. Low average anaerobic corrosion rates were measured for carbon steel and a very modest amount of alteration was identified on copper. The density and the initial form of the bentonite had a small influence on the rate of corrosion, across all materials. This paper summarises the results of the experimental programme obtained to date and discusses the relationship observed between exposure time and the evolution of the metal–bentonite interface for both carbon steel and copper.

In the Belgian supercontainer concept, a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research has...

Carbon steel is a candidate disposal canister material for high-level radioactive waste and spent fuel in the Swiss deep geological repository concept and so a long-term laboratory-based corrosion ...

This paper presents a state-of-the-art analysis of the expected degradation processes of a variety of candidate container materials for the disposal of high-level waste and/or spent nuclear fuel. The work, focusing on the most recent developments, has been performed under the auspices of the Implementing Geological Disposal Technology Platform in the context of an international conference hosted by the Nuclear Waste Management Organisation of Canada (NWMO). The scope of the analysis includes the expected corrosion and environmentally assisted cracking behaviour of copper, carbon steel and titanium in contact with relevant buffer materials (e.g. bentonite, cement) and in conditions expected in an underground disposal facility (long-term anoxic conditions). Considerations relative to the expected evolution of the environmental conditions (especially in the period following backfilling) are also presented. Beyond summarising the current state of knowledge, areas in which opportunities for international collaboration may be present are also highlighted. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Experimental evidence related to the interactions between steel corrosion and bentonite in deep geological repositories is reconsidered. The released Fe2+ interacts with the smectite and precipitates as Fe3+ when oxidised by residual immobile oxygen. This leads to the development of coloured fronts in the bentonite. The evolution of these fronts can be reproduced by a reactive transport model that takes account of the competition between diffusion and precipitation. Furthermore, two-phase flow modelling indicates that the consumption of water by the corrosion outpaces the diffusion of water through the bentonite, leading to shrinkage microfractures in bentonite that act as preferential pathways for corrosion products.

The Supercontainer is the reference concept for the post-conditioning of vitrified high-level radioactive waste and spent fuel in Belgium. It consists of a prefabricated concrete buffer that completely surrounds a carbon steel overpack. In this highly alkaline environment (pH ∼ 13.6) and under normal conditions (i.e. without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low uniform corrosion rates. This paper gives an overview of the status of the uniform corrosion, pitting corrosion and stress corrosion cracking behaviour of carbon steel expected during the waste disposal period.

A survey of the ionic species deposited on surfaces over periods up to 20 years was performed in facilities constructed to store stainless steel containers for radioactive waste or facilities broad...

The Swedish method for disposal of spent nuclear fuel in a deep geological repository (KBS-3) relies on the stability of the granitic bed-rock and two engineered barriers: a copper-cast iron canist...

In the Belgian Supercontainer concept for disposal of vitrified high level radioactive waste and spent fuel, a carbon steel overpack will surround the waste containers and be encased in a cementitious buffer material. In previous work the effects of radiation, temperature and chloride concentration on the anaerobic corrosion rate of carbon steel in an artificial alkaline porewater were measured and recently the effects of sulphur containing species, particularly sulphide and thiosulphate, on the anaerobic corrosion rate of aerobically precorroded carbon steel have been studied. Corrosion rates were measured by monitoring hydrogen evolution, by applying electrochemical methods and by gravimetric analysis. Corrosion product layers formed after several years’ exposure were analysed using focused ion bombardment (FIB) and SEM/EDX analysis. This paper summarises recent results, for experiments with and without sulphur species present. No increase in the anaerobic corrosion rate of pre-corroded carbon s...

In the UK, most intermediate level radioactive waste is packaged in stainless steel containers. It is important that containers should maintain their integrity for extended periods of storage prior to final disposal. A prototype 4 metre box fabricated from 304S11 stainless steel was monitored at an inland rural building for over twelve years to gain experience in monitoring environmental conditions and corrosion during storage. A wide range of different types of aerosol particles were observed on the surfaces and in the air. They contained corrosive ions such as chloride, as well as other anions such as sulfate and nitrate. The chloride deposition rate was between 0.1 and 4 μg cm−2 yr−1 depending on the orientation and location of the surface, with a chloride/sulfate ratio ranging from ∼0.3–2. The temperature and relative humidity typically ranged from 0–30°C and 40–90%, respectively. The greatest degree of corrosion developed on the base of the box, which had elevated chloride concentrations (10–140 μg cm−2). However, there was little evidence of corrosion propagation on the surface of the box and no evidence of stress corrosion cracking. The average pit propagation rates on a 316L coupon mounted next to the 4 m box were −1.

Intermediate-level radioactive waste is normally encapsulated in cementitious grout. However, for some wastes, grout may not be suitable and polymeric encapsulants are being considered as an alternative. One concern with such encapsulants is their long-term chemical stability and the possibility that release of aggressive degradation products could cause corrosion.This paper evaluates the potential for three polymeric encapsulants: two epoxy resins (the APS polymer system, (APS) and Alchemix 4760 (ALC)) and a vinyl-ester styrene (VES); to cause internal corrosion of stainless steel waste containers. The corrosion behaviour of stainless steel 316L in contact with each encapsulant was studied in saturated Ca(OH)2 solutions and deionized (DI) water, at 80°C, under non-irradiated and γ-irradiated conditions.In aerated, alkaline conditions, 316L was resistant to corrosion in all the conditions tested. However, in DI water, the pH fell to values as low as three due to release of acidic species from the polymers. The two epoxy materials (particularly APS) also released significant levels of chloride; VES did not. Chloride release appeared to be increased by γ-irradiation. As a result of the low pH chloride-containing environment created by the APS encapsulant, 316L experienced localized corrosion, whereas coupons in Alchemix 4760 and VES did not. Weight loss measurements correlated with visual observations. γ-irradiation appeared to increase the degree of corrosion.

This paper summarises recent experimental results from a programme that was carried out to investigate the effects of radiation on the anaerobic corrosion of carbon steel, in relation to the overpack that will be used in the Belgian supercontainer concept for radioactive waste disposal. Anaerobic corrosion rates of carbon steel were measured by monitoring hydrogen evolution using manometric gas cells and an autoclave and the corresponding electrochemical behaviour was investigated by measuring open circuit potential, linear polarisation resistance and alternating current impedance. The test medium was alkaline simulated pore water, at γ-irradiation dose rates of 0 and 25 Gy h−1, temperatures of 25 and 80°C and chloride concentrations of 0 and 100 mg L−1. The anaerobic corrosion rates exhibited a slow decline due to the formation of magnetite. Good agreement was found with weight loss measurements. A dose rate of 25 Gy h−1 had a negligible effect on gas generation rates.

The Supercontainer design is the preferred option for the underground disposal of high level nuclear waste in Belgium. It consists of a carbon steel overpack surrounded by a thick concrete buffer. In this high alkaline environment and under normal conditions (without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low uniform corrosion rates. The backbone of the RD&D strategy, which aims to provide confidence that the integrity of the overpack will be maintained at least during the thermal phase, is based on demonstrating that each localised corrosion mechanism (e.g. pitting corrosion, crevice corrosion and stress corrosion cracking), other than uniform corrosion, cannot take place under the high pH conditions prevailing within the Supercontainer (the ‘exclusion principle’). This paper gives an overview of the status of the RD&D programme related to the anaerobic uniform corrosion of the carbon steel overp...

To ensure the safe disposal of spent fuel in Sweden, SKB is planning to use the copper–iron canister in a granitic deep geological repository, surrounded by a compacted bentonite engineered barrier. In order to develop a deeper understanding of the internal corrosion behaviour of the design should a leak occur in the outer copper canister, a set of model canisters was set up in the Aspo underground laboratory in contact with bentonite with a range of densities. The environmental conditions and electrochemical corrosion behaviour were monitored using a range of techniques. Water analysis and electrochemical measurements indicated an increase in the corrosion rate of both iron and copper in contact with low density bentonite, and of iron only in experiments with no bentonite present. This behaviour may be attributable to microbial activity. The measured corrosion rate depends on the technique used and it will be necessary to confirm the measurements by removal and examination of weight loss coupons.

Carbon steel is a candidate material for radioactive waste containers in several countries. This paper summarizes and reviews the research that has been carried out within the United Kingd...

To ensure the safe encapsulation of spent nuclear fuel elements for geological disposal, SKB of Sweden are considering using a canister, which consists of an outer copper canister and a cast iron insert. Previous work has investigated the rate of gas generation due to the anaerobic corrosion of ferrous materials over a range of conditions. This paper examines the effect of radiation on the corrosion of steel in repository environments. Tests were carried out at two temperatures (30 °C and 50 °C), two dose rates (11 Gray h −1 and 300 Gray h −1 ) and in two different artificial groundwaters, for exposure periods of several months. Radiation was found to enhance the corrosion rate at both dose rates but the greatest enhancement occurred at the higher dose rate. The corrosion products were predominantly magnetite, with some indications of unidentified higher oxidation state corrosion products being formed at the higher dose rates.

In the horizontal emplacement concept (KBS-3H) for the disposal of radioactive waste, which is being developed in Sweden and Finland, copper canisters will be surrounded by bentonite buffer and placed in perforated steel containers in long horizontal boreholes in the crystalline bedrock, at a depth of ≈500 m. Under the chemical conditions in a deep repository, it is possible that the release of iron from the steel containers could influence the physico-chemical properties of the bentonite, for example, by exchange of the interlayer ions. In order to gain further insights into this process, an experimental study was undertaken, to investigate the mode of iron uptake into bentonite and the extent of changes induced in the basic physico-chemical properties of bentonite. The samples were taken from long-term anaerobic corrosion tests of carbon steel or cast iron in compacted bentonite (Na/Ca-bentonite: Volclay MX-80, ∼4% Fe 2 O 3 ) in contact with a simple artificial groundwater at 30 °C or 50 °C. A range of analytical techniques was applied to samples of corrosion product on carbon steel and cast iron and to the bentonite surrounding the corroding specimens. Corrosion products and bentonite samples were analysed using scanning electron microscopy (SEM), electron microprobe analysis (EPMA), Raman spectroscopy, X-ray diffraction (XRD) and Mossbauer transmission spectroscopy. In addition, the bentonite samples were analysed using Fourier transform infra-red spectroscopy (FTIR), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) and selected area electron diffraction (SAED), exchangeable cation analysis and cation exchange capacity (CEC) measurements. Hydraulic conductivity and swelling pressure were also measured. From visual observation, the corrosion product formed on the carbon steel in bentonite was less voluminous than that formed on steel in artificial porewaters with no bentonite, although previous work showed that the corrosion rates were slightly higher in the presence of bentonite. The Raman spectroscopy analysis showed that corrosion products on the surface of carbon steel and cast iron consisted of an inhomogeneous mixture of magnetite, hematite and goethite. The predominant species was magnetite. In the bentonite, the concentration of iron decreased with increasing distance away from the iron–bentonite interface, with local iron concentrations as high as 20 wt% in some experiments. The total iron content of the bentonite in contact with corroding carbon steel wires increased by several percentage points during the experiments and the cation exchange capacity of the bentonite was reduced. After contact with corroding steel wires the hydraulic conductivity of MX-80 increased substantially. The results of the analyses were consistent with ion exchange of Fe 2+ ions with Na + ions in the montmorillonite interlayer positions but the exact chemical location of all the additional Fe 2+ ions is currently uncertain. There was no evidence for the transformation of montmorillonite to an iron-rich clay mineral phase.

In Sweden, high-level radioactive waste will be disposed of in a canister with a copper outer container and a cast iron or carbon steel insert. If the iron insert comes into contact with a...

In Sweden, high-level radioactive waste will be disposed of in a canister with a copper outer container and a cast iron or carbon steel insert. If the iron insert comes into contact with anoxic geological water, anaerobic corrosion will occur. This paper presents a study of the electrochemical aspects of anaerobic corrosion of carbon steel in artificial Swedish granitic groundwaters. The electrochemical measurements confirm that anaerobic corrosion will lead to the generation of hydrogen, but the rate of corrosion will be anodically limited by the formation of a corrosion product film. The corrosion rate was unaffected by hydrogen pressures up to 100 atm.

The Supercontainer (SC) design is the preferred option for the final disposal of high level nuclear waste and spent fuel in Belgium. The SC consists of a carbon steel overpack surrounded by a very thick concrete buffer, contained within a stainless steel envelope. In this highly alkaline environment of the annulus and under normal conditions (without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low and almost negligible uniform corrosion rates. This paper discusses the modeling efforts simulating the evolution of various parameters that can potentially influence the corrosion processes (temperature, pH, saturation degree and concentration of aggressive species). The outcome of the Belgian experimental program to study the passive uniform corrosion of carbon steel in concrete is also addressed. Long-term uniform corrosion rates are determined using different independent techniques (hydrogen gas measurements by means of manometric gas cells or pressure transducers, long-term passive current density measurements).Copyright © 2013 by ASME

The ACHILLES expert system provides broad ranging advice on corrosion, protection, material selection and failure diagnosis. It contains modules dealing with nine aspects of corrosion, one of which is stress corrosion cracking (SCC). Each module was based on information provided by an expert in the form of a document or “resource digest”. The “Aspects of Stress Corrosion Cracking” module deals with the following topics: introduction to SCC, diagnosis, detection, monitoring and prevention of SCC, SCC of steels in various environments and SCC in specific plant items. Two example consultations are presented.

Stress corrosion crack growth rates have been measured for mild steel in a 1 N sodium phosphate solution adjusted to pH 6, using slow strain rate tensile and cantilever bend tests. It was found that de-aeration of the test solutions significantly reduced the stress corrosion susceptibility. Repassivation kinetics have been measured using the potential step and drop-weight straining wire techniques. Calculations of crack growth rates using the film rupture-dissolution mechanism agree well with the observed crack velocities. The effect of de-oxygenation can be explained in terms of its influence on the passive film properties.

In the horizontal emplacement concept (KBS-3H) for the disposal of radioactive waste, which is being developed in Sweden and Finland, copper canisters with cast iron inserts will be surrounded by bentonite buffer and mounted in perforated carbon steel support structures in boreholes within the bedrock. The groundwater will be reducing, leading to anaerobic corrosion of the ferrous material. It is important to understand both the effect of bentonite on the corrosion behaviour of the steel and the effect of the corrosion products on the performance of the bentonite. Previous work on the corrosion of steel in bentonite was extended to investigate a wider range of conditions, including the possible effects of alkaline plumes released from concrete support structures and the effect of chloride concentration and temperature on the corrosion rate of steel in bentonite. Corrosion rates were measured by collecting hydrogen produced by the anaerobic corrosion of iron. In addition, a range of analytical techniques was applied to study the composition and morphology of the corrosion products and the distribution and chemical state of the iron released into the bentonite. Comparison was also made between corrosion in compacted bentonite and artificial bentonite porewater. In the presence of bentonite, the corrosion product layer was relatively thin compared to fully aqueous conditions, probably because the ferrous ions released by corrosion exchanged with the bentonite interlayer or attached to the surface of the bentonite grains, rather than forming a separate iron oxide phase.

In Sweden, spent nuclear fuel will be encapsulated in sealed cylindrical canisters, consisting of a cast iron insert and a copper outer container. The canisters will be placed in a deep geologic repository and surrounded by bentonite. If a breach of the outer copper container were to occur the cast iron insert would undergo anaerobic corrosion, forming a magnetite film whose volume would be greater than that of the base metal. In principle there is a possibility that accumulation of iron corrosion product could cause expansion of the copper canister. Anaerobic corrosion rates are very slow, so in the work described in this paper reference was made to analogous archaeological materials that had been corroding for long periods in natural anoxic aqueous environments. This paper describes a number of archaeological artefacts containing iron and copper corroding in constrained geometries in anoxic natural waters. No evidence has been obtained which would suggest that severe damage is likely to occur to waste canisters as a result of expansive corrosion of cast iron under repository conditions.

In Sweden, it is proposed that spent nuclear fuel should be encapsulated in sealed cylindrical canisters for disposal in a geologic repository. The canisters would consist of a thick ferrous inner container and a copper overpack. If mechanical failure of the copper overpack occurred, allowing water to enter, there would be a build up of ferrous corrosion product, which could induce stresses in the outer copper canister. This paper describes an apparatus, the ‘stress cell’, which was designed to measure the expansion caused by the anaerobic corrosion of steel under compressive loads. The apparatus consisted of a stack of steel and copper discs, which were immersed in simulated anoxic groundwater. A system of levers amplified the change in height of the stack, and the displacement was measured using sensitive transducers. Three cells were set up; two contained alternate mild steel and copper discs, and the third, a control cell, consisted of alternate stainless steel and copper discs. A slight contraction of the control cell was observed but no expansion was measured in the mild steel - copper cells.In parallel, coupons of mild steel and cast iron were corroded in anoxic, artificial groundwater at 50°C and 80°C for several months. The coupons were examined by atomic force microscopy (AFM) to determine the mechanical properties and the structure of the corrosion product films, and X-ray photoelectron spectroscopy (XPS) to identify the chemical composition of the film.

In Sweden, it is proposed that spent fuel should be encapsulated in sealed cylindrical canisters for disposal in a geologic repository. The canisters would consist of a thick ferrous inner container and a copper overpack. If mechanical failure of the copper overpack occurred, allowing water to enter, the ferrous inner container would corrode anaerobically and liberate hydrogen. The rate of hydrogen generation due to the anaerobic corrosion of steel in anoxic groundwater has been measured using barometric cells. The aim of the work presented in this paper was to measure the redox potential, Eh and pH in the presence of anaerobically corroding steel, in a barometric cell. Two specially designed barometric cells were constructed. They were equipped with a silver chloride or calomel reference electrode, a gold Eh electrode, a glass electrode, and a steel electrode. The electrodes were allowed to stabilize in anoxic artificial groundwater and then a mass of pickled steel wire was introduced into the test cell. As the wires were added, the redox potential rapidly became more negative due to the rapid consumption of the residual oxygen. The corrosion potential of the steel was stable and a slow drift in pH was observed. The results are compared with the results of geochemical modelling. Extension of the work to investigate the electrochemical parameters in the presence of dissolved uranium species is discussed.

This paper describes recent results from an investigation of the effects of -radiation on the anaerobic corrosion of carbon steel in cement, in relation to the Belgian Supercontainer Concept for radioactive waste disposal. Anaerobic corrosion rates were measured by monitoring hydrogen evolution and the corresponding electrochemical behaviour was investigated by measuring open circuit potential and linear polarisation resistance. The test medium was alkaline simulated porewater, at -irradiation dose rates of 0 and 25 Gy hr −1 , temperatures of 25 ◦ C and 80 ◦ C and chloride concentrations of 0 and 100 mg/l. The effects of radiation on the corrosion behaviour were found to be small. The reference design for the Belgium Supercontainer for disposal of high-level nuclear waste and spent fuel consists of a 30 mm thick carbon steel cylindrical vessel ('the overpack') surrounding 309 grade stainless steel waste canisters. The overpack will be surrounded by a cementitious buffer material, which may or may not be encased in a stainless steel vessel ('the envelope'). This paper is concerned with the anaerobic corrosion processes that may affect the carbon steel overpack within the Supercontainer. The carbon steel will be exposed to alkaline porewater in the cementitious buffer or in the alkaline material which may be used as a filler in the annulus between the cementitious buffer and the overpack. After a relatively short period the interface between the steel and alkaline porewater will become anoxic as residual oxygen in the repository is consumed by aerobic corrosion and microbial activity. Low concentrations of chloride (typically 100 ppm) from the groundwater may penetrate the buffer and reach the surface of the overpack. Following a review of the corrosion issues affecting the Supercontainer design an experimental programme was initiated to investigate (i) the possible effect of gamma radiation on the anaerobic corrosion rate of carbon steel in cementitious porewaters and on the nature of the corrosion products formed, and (ii) the effect of radiation on the electrochemical and corrosion behaviour of carbon steel corroding anaerobically in simulated concrete porewater conditions. Previous publications have reported earlier results from this programme (1, 2) for both gas generation and electrochemical measurements. The aim of this paper is to provide an update on this work programme, with the main focus being on the results of the electrochemical measurements, although the results from the gas generation experiments are also shown for comparison. In essence the work programme involved setting up test cells containing representative corrosion systems and exposing them to controlled gamma radiation

ABSTRACT The nucleation of (Ba, Sr)S04 scale has been studied on different surfaces representative of those likely to be encountered in oil production. The amount of scale formed and the efficiencies ofthree typical scale inhibitors depended on the surface used. Similar results were obtained from mixtures of seawater with either synthetic or real formation water. INTRODUCTION Mineral scales are frequently formed in oil production, usually as the result of changes in the temperature or pressure of produced fluids, or the mixing of incompatible formation and injection waters. The scale may form a precipitate in thebulk fluid, and be carried along with it in suspension, or it may nucleate on the walls of containing vessels and grow to form an adherent scale. This adherent layer can reduce the flow of fluids in tubulars, prevent the proper functioning of chokes and safety valves, and concentrate some radioactive species from produced fluids to an extent sufficient to create a local radiation hazard. Some of the suspended scale may betransported to the walls to form a particulate deposit that is more porous, mechanically weaker, and easier to remove than those formed by direct nucleation on the surfaces. Despite the widespread occurrence of scale in oil production and other industrial and domestic situations, relatively little attention has been paid to the distinction between adherent and non-adherent scale. This paper describes some of the work being undertaken on scale nucleation on surfaces, and the effects of scale inhibitors on its inhibition and growth, in an on-going research programme at Harwell, supported by a number of oil producing companies. In view of the preponderance of mixed barium and strontium sulphate scaling in North Sea oil production as a result of mixing formation waters and seawater1, work has concentrated on (Ba, Sr)S04 scale formation on a number of surfaces representative of those likely to be encountered both downhole and topside. THE NUCLEATION PROCESS Nucleation of solid deposits is likely to be affected by the nature of the surface involved. The free energy change for the formation of a solid particle in a liquid can be written as(Available In Full Paper) where ø the driving force for the phase change, is given by(Available In Full Paper) in which S is the saturation index or saturation ratio, n is the number of molecular units in the particle,? the surface energy of the particle and A its surface area2. The change in G as the part1cle grows is given by(Available In Full Paper) where ? is the molecular volume and r is a measure of the radius of the particle that also allows for its shape. This change in free energy is thus affected by the saturation ratio, which isdetermined by the chemical composition of its surroundings and their temperature and pressure, and the energy required to create the new surface.

X-ray photoelectron spectroscopy (XPS) measurements have been made on a range of cadmium and tellurium compounds, including single-crystal wafers of CdTeO 3 and CdTe 2 O 5 , in order to identify the nature of anodically formed oxide films on Hg 0.8 Cd 0.2 Te. We find that the oxygen Auger parameter is significantly different for CdTeO 3 and CdTe 2 O 5 . Measurements of this parameter suggest that the most likely major constituents of the film are TeO 2 and CdTeO 3 . Significant differential sputtering and chemical reduction effects resulting from Ar + ion bombardment were observed for TeO 2 , CdTeO 3 and CdTe 2 O 5 . These effects cast doubt on the validity of quantitative XPS depth profiles of the anodic oxide.

Previous work has used X-ray photoelectron spectroscopy to examine the surface compositions of aluminium-alloy substrates subjected to various surface pretreatments prior to bonding. It was proposed that the presence of magnesium in the oxide structure adversely affected the service-life of adhesive joints when they were exposed to aqueous environments. The present work further explores this correlation by examining a range of aluminium alloys, basically of the same composition except for the level of magnesium in the alloy.

X-ray photoelectron spectroscopy and scanning electron microscopy have been used to investigate the surface chemistry of an aluminium-alloy which has been pretreated by various industrial methods commonly employed prior to adhesive bonding. The fracture surfaces of butt joints, consisting of the pretreated alloy bonded with an epoxy adhesive, have also been studied. The analyses have been conducted before and after exposure of the specimens to water, the main hostile environment that structural adhesive joints usually encounter. It is suggested that the concentration of magnesium, in the form of magnesium oxide, on the pretreated aluminium-alloy surface may be an important factor in influencing the durability of adhesive joints.

A long-term in situ corrosion experiment is ongoing in the Mont Terri Underground Research Laboratory in Switzerland to (i) measure the in situ corrosion behaviour of carbon steel in compacted bent...