Samuel Jouen

Atmospheric corrosion of nickel in various outdoor environments

As part of a field exposure program in the north-west of France on atmospheric corrosion of metal and alloys, this study presents the results of the behaviour of nickel panels exposed in industrial, urban and rural atmospheres. Mass measurements were investigated during the exposure and adherent corrosion layers were followed by means of several methods of analysis: Fourier transform infrared reflection–absorption spectroscopy, X-ray diffraction and scanning electron microscopy with X-ray microanalysis. In order to determine all the chemical species formed in the corrosion layers, corrosion products released from the surface by rainfall were also studied by collecting the streaming water from the nickel surfaces. Anionic and cationic quantities in the streaming water were determined respectively with ionic chromatography and polarography. The nickel attack appears as a pitting corrosion process accompanied by the formation of soluble corrosion products in dry exposure periods, these being regularly dissolved by rainfall events. Pits are associated with the formation of nickel salts, mainly sulphates and chlorides with small amounts of nitrate, and surrounded by carbonate species. The corrosion rate increases from rural to industrial areas.

Simultaneous copper runoff and copper surface analysis in an outdoor area

Simultaneous copper runoff and copper surface analysis has been performed during a field exposure in a French industrial area. Corrosion layer composition was studied with fourier transform infrared reflection-absorption spectroscopy, x-ray diffraction and scanning electron microscopy with energy-dispensive scattering analysis, revealing cuprite, basic copper sulphates (brochantite and posjnakite) and copper sulphate pentahydrate (CuSO 4 .5H 2 O) as the main corrosion products after 3 months of exposure. In order to determine the soluble corrosion compounds carried with rain, the water streaming over a copper coupon was collected and analysed by means of ionic chromatography and potentiometric stripping analysis. Significant sulphate and copper concentrations were detected in water and interpreted as resulting from the dissolution of copper sulphate compounds.

FT-IR Microscopic Base Imaging System: Applications for Chemical Analysis of Zn and Ni Atmospheric Corrosion

The possible use of an FT-IR imaging system for surface studies of atmospheric corrosion products on zinc and nickel samples has been explored. Samples have been exposed in an urban site located at Rouen in France. Corrosion products, detected by means of energy-dispersive spectrometry/X-ray diffraction (EDS/XRD) and FT-IR spectroscopy, are mainly Zn4CO3(OH)6·H2O, ZnSO3·nH2O, Zn4SO4(OH)6·nH2O, and NiSO4·xH2O. IR microspectroscopy and mapping techniques allow the observation of the heterogeneous distribution of chemical species on sample surfaces. While the zinc corroded surface seems uniform, inhomogeneity in the development of carbonate and hydroxysulfate compounds in layers is observed. The imaging chemical analysis enables the assignment of the 1550 cm−1 absorption band of the corrosion product to zinc hydroxycarbonate. The corrosion mechanism observed on nickel is pitting corrosion. Pit size, chemical mapping, and 3-D visualization determined from SEM/EDS and FT-IR maps are very similar.

Atomic-scale characterization of the nucleation and growth of SnO2 particles in oxidized CuSn alloys

The internal oxidation of Sn was investigated to understand the oxidation kinetics of monophase CuSn alloys. SnO 2 particles were characterized by analytical transmission electron microscopy. The orientation relationship between SnO 2 and Cu was determined with a special emphasis on the atomic-scale structure of Cu/SnO 2 interfaces (misfit dislocations and chemical structure). Habit planes with a pure oxygen plane terminating the SnO 2 phase are greatly favored and large misfits promote the growth of plate-shaped precipitates.

Scaling and internal oxidation of α-CuSn alloy

Abstract α-CuSn alloy containing 8.2 wt% tin oxidized in laboratory air at 610°C is studied for its microstructural evolution with time. A cross-sectional study of the sample after oxidation shows the presence of a multilayered oxide scale on the surface and internal oxidation. Oxide morphology is expected to give an insight on undergoing oxidation mechanism. Analysis shows that SnO2 is present in porous morphology close to the substrate as clusters and not as a continuous layer; and as an internal oxide, occurring non-uniformly throughout the sample surface.