Corrosion behavior of iron in cementitious solution at 80°C in anoxic condition

International audienceThe Belgian reference concept for high-level radioactive waste packaging proposed by ONDRAF/NIRAS is called Supercontainer. The design of the Supercontainer includes a stainless-steel liner, a concrete buffer and a carbon steel overpack containing one or several waste canisters. An objective of the concrete buffer is to maintain high alkaline conditions on the surface of the overpack during underground disposal of these wastes. In these conditions (alkaline and anoxic conditions), a passive film forms on the surface of the steel, resulting in very low and almost negligible uniform corrosion rates (passive dissolution). This film is generally composed of a double layer an inner layer, accounting for passivity, and a more or less porous outer layer. The latter is in contact with the environment and is formed by precipitation of elements in solution. The presence of silicon and cations from the cementitious environment could lead to neo-formed phases such as ferrous-silicates or phyllosilicates possessing corrosion inhibiting properties. The aim of this work is to study the impact of the cementitious materials during the corrosion at 80DC in anoxic media by characterizing the layer formed during the corrosion process. To ensure these measurements, iron plates were corroded in solution representative of a cementitious environment (at 80DC and under anoxic conditions). Evolution of the nature and growth of the corrosion layer is studied on samples after several duration tests. Corrosion products are characterized by means of several analytical techniques such as scanning electron microscopy, Raman micro-spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and transmission electronic microscopy. Results have revealed evolution of composition as a function of time. Layers are mainly composed of magnetite and others phases containing iron, calcium and silicon

Que deviendraient nos réalisations architecturales, industrielles ou artistiques si l'humanité disparaissait ?

National audienceDans cette expérience de pensée, nous imaginons comment le monde industriel, architectural et artistique évoluerait si les humains disparaissaient. L'exposé sera structuré selon des allers retours entre les représentations d'ouvrages de science fiction et ce que nous dit la science sur ces sujets (dégradation des ouvrages en béton et développement de la corrosion)

PASSIVATION, LOCALISED CORROSION AND GENERAL CORROSION OF STEEL IN CONCRETE AND BENTONITE. THEORY AND EXPERIMENTALS

International audienceIt has been argued in various places that prediction of the behaviour of corrosion allowance materials is easier than for passive materials which may undergo localised corrosion.The mechanisms of localised corrosion are presented in this paper, together with supporting experimental facts. Important parameters are pH and aggressive ions in the environment, protection potential and changes of electrode potentials with time

Eau de mer synthétique biochimique pour essais de corrosion

Une eau de mer synthétique est mise au point afin de reproduire les résultats obtenus sur la tenue des aciers inoxydables en eau de mer naturelle. Cette nouvelle eau de mer synthétique est basée sur la composition chimique de l’eau de mer et sur les mécanismes d’action des bactéries marines présentes dans les biofilms sur les alliages passivables. Son originalité est dans l’addition d’enzymes qui simulent l’augmentation de la vitesse de la réaction cathodique observée en eau de mer naturelle. Les résultats des essais de corrosion par effet de crevasse dans cette nouvelle eau de mer synthétique biochimique sont tout à fait en accord avec le comportement connu des aciers inoxydables en eau de mer naturelle

Corrosion and Green Chemistry

International audienc

Carbonation induced corrosion of steel in concrete based on low pH binders

International audienceNowadays, with an increase of awareness of society and industry on the environmental footprints, there is an increasing need in innovative concrete binders, usually secondary resources and by-products, utilised as partial or full substitution of ordinary Portland cement. Most of these materials have beneficial particle size distribution and/or chemical composition, leading to concrete with lower permeability and higher electrical resistivity. At the same time, their different chemistry leads to changes in pH values of pore solution and in concrete microstructure, which could consequently lead to changes in corrosion properties of steel embedded in these types of concrete. These changes in corrosion properties are especially highlighted when concrete is exposed to long-term carbonation process.The aim of this paper is to research the difference in corrosion behaviour of steel in carbonated concrete based on different types of low pH binders. In the paper results on four concrete mixes are presented, all having different type of binder reference mix with ordinary Portland cement, mix with high volume of fly ash and silica fume, mix with blast furnace slag cement with the addition of nanosilica and mix with high volume of metakaolin and lime. After curing reinforced concrete samples were carbonated at 3% CO2 to ensure representativeness with natural carbonation. During early ages and after carbonation changes of corrosion potential, corrosion rate and electrical impedance parameters are monitored and discussed in the paper. Corrosion behaviour was connected to the changes in microstructure of these different types of concrete during carbonation

Electrochemical behavior of metallic materials used in seawater—interactions between glucose oxidase and passive layers

International audienceSix materials (stainless steel, nickel-base alloy, titanium, chromium, nickel and admiralty brass) are tested in chemical and biochemical synthetic seawaters. The biochemical seawater contains enzymes catalyzing oxidation of glucose (glucose oxidase), simulating the action of natural biofilms. The evolutions of free corrosion potential (Ecor) versus time, and of cathodic and anodic reactions are compared with those obtained in natural seawater. Then, electrochemical behavior is related to semi-conducting properties of passive films. When glucose oxidase is present, increase of Ecor versus time is only reported for materials presenting a n-type semi-conductor passive film, and whose cathodic reaction current is increased. On the contrary, when passive layers are p-type semi-conductors, cathodic and anodic reactions are increased, and lead to a global Ecor constant with time of immersion. It appears that interaction between bacteria, medium and materials includes evolution of semi-conducting properties of passive layers

Contribution to the micro-mechanical analysis of corrosion products formed during long-term carbonation induced corrosion of steel

International audienceUse micro-indentation to distinguish different phases of corrosion products, confirmed with Raman and SEM Obtain spatial distribution of different phases, in relation to the surface of the steel Compare mechanical properties of same phases at different ag