Search results for "CORROSION"
showing 10 items of 456 documents
Visually low-impacting methods for the measurement of parameters related to IAQ risk indicators in exhibition halls
2021
Microclimate for cultural heritage plays a fundamental role in the degradation process of artefacts exhibited in museums. Generally, the Indoor Air Quality (IAQ) monitoring inside museums is based on conventional measurements of thermo-hygrometry parameters and longtime averaged measurements of atmospheric pollutants’ concentration. Unfortunately, all these approaches require electric supply and are usually characterized by a noticeable visual impact on the exhibition space, which clearly negatively affects the visitors’ experience. This paper intends to revisit and discuss a methodology (and its test application on field, to estimate the risk of damage of three artefacts displayed in an ol…
Investigation of structure, stability, phase composition and magnetic ordering in ultrathin iron/nickel films
1995
By thermal and chemical treatment of Langmuir-Blodgett (LB) films, oxidic and metallic Fe and Ni layers can be prepared. The films are characterised, where differences e.g. in the lateral homogeneity are found. The metallic Fe containing samples show a higher corrosion stability as compared with films prepared by other coating techniques. Mixed Fe/Ni oxidic and metallic layers, respectively, are prepared, where the Ni concentration in the oxidic films can be determined as a function of the ratio of initially transferred numbers of LB layers. The phase composition of the metallic Fe changes systematically with the Ni concentration.
Exploring corrosion protection properties of alkyd@lanthanide bis-phthalocyanine nanocomposite coatings
2017
Organic coatings have been widely used to protect carbon steel pipelines from external corrosion; however, they often suffer from permeability and weak adhesion. Here we show that synthetic lanthanide bis-phthalocyanine complexes, LnPc2 (Ln = lanthanide metal, Pc = C32H16N8 denotes the phthalocyanine ligand) can be used to form new nanocomposite coatings to provide corrosion protection to the underlying carbon steel pipelines. Electrochemical studies (EIS and potentiodynamic polarization) showed that the incorporation of LnPc2 compound (PrPc2, SmPc2 and HoPc2) additives with alkyd coating, leads to a significant increase in the corrosion resistance of carbon steel in 0.5 M HCl solution. The…
Coupling of electrochemical, electrogravimetric and surface analysis techniques to study dithiocarbamate/bronze interactions in chloride media
2018
International audience; Interaction between ammonium pyrrolidinedithiocarbamate (PDTC) and bronze in 30 g L-1 NaCl was investigated at several concentrations between 0.1 and 10 mM by means of various electrochemical and spectroscopic techniques. Electrochemical measurements revealed a fast adsorption process of PDTC on Cu and Pb and the formation of a thick insulating and protective film with a high surface coverage. At high concentrations, PDTC prevents oxides formation. Surface analyses confirm PDTC adsorption on bronze mainly via interaction between sulphur atoms and Cu sites to form Cu I-PDTC complex.
Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation.
2011
Abstract In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10–15% for female adults and 1–3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni–Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni–Cr dental alloys. Microstructure characterization, corrosion r…
Instability and bistability during the growth of a corrosion scale on metals and alloys
1986
This paper summarizes the main results for the interpretation of the self organized corrosion scales observed in oxidation or sulfidation of some metals or alloys. It consists also of a reconsideration of the classical theoretical concepts used in Reactivity of Solids. It proposes new theoretical tools that have been fruitfully utilized in other topics : non linear and coupled processes, stability analysis and bifurcation theory. Some examples are developed, where the corrosion kinetics at high temperature are interpreted in term of chemical bistable system able to oscillate spontaneously and mechanochemical couplings are also taken into account. In according with experimental results, all …
A study of electrochemically-induced corrosion of low carbon steel in a medium modelling acid rain
1994
Complementary electrochemical, spectrophotometric and electron microsopic investigations were made in addition to the conversion electron Mossbauer spectroscopic (CEMS) measurements to learn more about the mechanism of corrosion of low carbon steel samples in aqueous sulfate and sulfite containing sulfate solutions (pH 3.5, 6.5 and 8.5). Passivation of iron in pure sulfate solution was studied in detail in earlier papers. In the present work, we used a solution containing both sulfate and sulfite anions to obtain more information about the effect of acid rain on low carbon steel samples. The compositions and thicknesses of the passive films formed due to the electrochemical treatments were …
Electrochemical and conversion electron mössbauer study of corrosion induced by acid rain
1993
Abstract The passivation of low carbon steel was studied in aqueous solution of 0.5M Na2SO4 +0.001M NaHSO3 (pH 3.5, 6.5 and 8.5) which can be considered as a model of acid rain. The used conversion electron Mossbauer spectroscopy (CEMS) with the complementary electrochemical investigations proved that the sulfite ions induce pitting corrosion at pH 3.5 and 6 5 while the measurements showed much weaker pitting at pH 8.5. The compositions and thicknesses of the passive films formed during the electrochemical treatments are determined from the CEM spectra. Only γ-FeOOH was found on the surface of the samples at pH 6.5 and 8.5. Nevertheless, at pH 3.5 the sextet belonging to Fe3C appears in the…
High magnification SEM observations for two types of granularity in a high burnup PWR fuel rim
1998
Abstract Rim microstructure of an UO2 pellet irradiated up to 61 GWd/tU, observed with high magnification scanning electron microscopy, presented two types of subgrains: polyhedral and round subgrains. Round subgrains were also observed on the surface of fabrication pores along the pellet radius. These round-shaped subgrains seem to be associated to free surface rearrangement. This new type of round subgrains was proved to be independent of the rim effect. Observations of the fuel structure in the vicinity of rim area evidenced two types of defects specific to rim effect: planar defects and small intergranular pores. Hypothesis is made that the accumulation of planar defects could generate …
Magnetic field effect on the corrosion processes at the Eurofer–Pb–17Li flow interface
2015
Abstract Structural and elemental analyses of the RAFM steel (EUROFER 97) interface with flowing Pb–17Li eutectic (velocity 5 cm/s at 550 °C, 1000 h) under the action of a strong magnetic field (B = 1.7 T) were performed using optical microscopy, SEM, confocal microscopy, precision micro-hardness methods, SIMS and point or line-scan EDX analyses. The results show that the magnetic field induces a faster crushing of martensite into the grains, a deeper dissolution of grain boundaries, an enhancement of the Fe and Cr mass transfer and a fast detachment of corrosion layers due to MHD effects.