Copper corrosion in soil: influence of chloride contents, aeration and humidity |
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Authors: | F. Soares Afonso M. M. M. Neto M. H. Mendonça G. Pimenta L. Proença I. T. E. Fonseca |
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Affiliation: | 1. CCMM, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016, Lisbon, Portugal 2. Departamento de Química Agrícola e Ambiental, Instituto Superior de Agronomia, Tapada da Ajuda, TU Lisbon, 1349-017, Lisbon, Portugal 3. Instituto de Soldadura e Qualidade (ISQ), Av. Professor Cavaco Silva, 33, Tagus Park-Talaíde, 2781-994, Porto Salvo, Oeiras, Portugal 4. Instituto Superior de Ciências da Saúde Egas Moniz (ISCSEM), Quinta da Granja, Monte de Caparica, 2829-511, Caparica, Portugal
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Abstract: | The corrosion of copper in a typical Portuguese soil was studied. The original soil was characterised, and modifications were produced by adding chloride, and HClO4 solutions, or by increasing its relative humidity. The aggressiveness degree of the various soil samples was determined. Copper coupons exposed for 3 months in the original and in the modified soil samples were analysed. The average corrosion rates determined from gravimetric data were in good correlation with the soil aggressiveness. The morphology of the corroded copper surfaces, with and without corrosion products, was analysed by visual observation, optical microscopy and scanning electron microscopy. Energy dispersive spectroscopy was used for the semi-quantitative analysis of the corrosion products and X-ray diffraction spectroscopy to identify the crystalline products. Cuprite has been identified on the copper samples corresponding to the interfaces Cu|S6 and Cu|S8, plus paratacamite on the copper coupon exposed to the soil with higher concentration of chloride (S6). Polarisation curves of copper samples in neutral solutions made by adding different amounts of chloride ions to the soil washing water, under deaereated conditions, were recorded and analysed. The passivity breakdown potential has shown, as expected, a displacement to the cathodic direction as the Cl− ion concentration increases. |
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