Inibidores naturais de corrosão extraidos em vegetais tropicais

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Metal corrosion can be minimized or inhibited using corrosion inhibitors. The aim of this work was the extraction of inhibitors from natural sources. Peels of mango (Mangífera inidica L.) and of avocado-pear (Perfea americana L.) and cabbage (Brassica oleracea L.) leaves were used. Successive extractions were performed at high temperature using the crushed vegetables with solvents of increasing polarity. Test specimens of 1020 steel with 1 cm surface area were cast. The aqueous and ethanolic extracts showed the presence of substances with inhibiting properties when sulfuric acid was used as corrosive agent. The inhibiting efficiencies of mango, avocado-pear and cabbage were, respectively, 81, 80 and 71%, as measured by weight loss. Also, direct extraction with water, at 80°C, rendered a corrosion inhibitor solution when sulfuric acid was used as above, with an efficiency of 69%. Electrochemical impedance measurements and optical and scanning electron microscopy showed that the inhibiting species adsorb in the metallic surface. Infrared spectra and nuclear magnetic resonance indicated that the active species contain carboxylic, carbonyl and hydroxyl groups, which could attach to the surface. Mango extract was further analyzed in respect to temperature effect, showing the same efficiency up to 40°C and decreased efficiency at higher temperatures. The charge transfer resistance changed from 54.9 to 0.23 W and the double layer capacitance changed from 7.5 x 10 to 1.2 x 10 F cm in the range of 25 to 60°C. The results obtained in this work point to the feasibility of sing theses vegetables to commercially extract corrosion inhibitors.

ASSUNTO(S)

plantas tropicais aço manga abacate materiais resistentes a corrosão repolho

ACESSO AO ARTIGO

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