XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society PD 02
Copper corrosion in soils contaminated with chloride ions
Carla Barradas Dias 1 , M. M. M. Neto 1,2 , I. T. E. Fonseca 1
1 CCMM, Departamento de Química e Bioquímica da Universidade de Lisboa, Campo Grande
Ed C8,1749-016 Lisboa, Portugal
2 UIQA, Instituto Superior de Agronomia, TU Lisbon, Tapada da Ajuda, 1349-017 Lisboa, Portugal
carlabarradasdias@gmail
Soils are, in general, very complex matrices; physical conditions (pH, porosity, humidity
degree, oxygenation and conductivity, among others) and the presence of different ions
in soils may induce corrosion on buried metallic structures and pieces leading to its
deterioration. Toxic species released during the corrosion processes can affect soils
causing serious contamination problems. On the other hand, the deterioration of metals
such as copper and copper alloys used in buried electricity earthing systems may give
rise to safety problems.
Thus, studies on the behaviour of metallic samples, buried in soils with different degrees
of agressivity, are an important topic in materials as well as in environmental sciences.
Following previous studies 1, we have carried on working in this type of subject.
The present communication reports a study performed with a set of copper samples
buried, during a 3 month period, in soil samples with different degrees of aggressivity,
particularly, with different chloride contents (Cl - : 0.01 to 0.5 M). The initial soil
sample was characterized and the other modified soil samples were prepared by the
addition of different amounts of chloride ions.
Copper coupons were characterized before the test and after being removed from the soil
samples in which they have been buried. The analysis was performed by visual
observation and different techniques, namely optical microscopy, gravimetry, scanning
electron microscopy (SEM) and X-Rays diffraction spectroscopy (DRX).
Another set of experiments was performed with a copper electrode immersed in
solutions made with different chloride concentrations, using the soil washing water as
solvent (Cl - : 0.01 to 0.5 M), at constant pH of 6.4 (pH value of the original soil
sample). The effect of acidifying the medium was also studied; studies were performed
at pH 6.4, 5.8 and 4.8.
Acknowledgments: CCMM (Centro de Ciências Moleculares e Materiais) and UIQA (Unidade de
Investigação de Química Ambiental) are grant aided by F CT (Fundação para a Ciência e
Tecnologia).
References
[1] Afonso, F. S.; Neto, M. M. M.; Mendonça, M. H.; Pimenta, G.; Proença, L.; Fonseca, I. T. E., J
Solid State Electrochem., 2009, 13, 1757.
September, 811, 2010. ISEL - Lisbon 84