Avaliação da eficiência do pó de semente de abacate (Persea americana) como inibidor da corrosão do aço galvanizado em meio ácido

Abstract

Galvanized steel has good resistance to corrosion when exposed to mild environments, such as normal atmospheric conditions or natural waters, due to the cathodic protection provided by the zinc coating layer and the formation of basic zinc carbonate, which is a protective compound produced in urban atmospheres with humidity and carbonic gas. However, in more aggressive media, such as polluted atmospheres containing acidic substances and humid and confined environments, the corrosion resistance of galvanized steel is low, requiring complementary protective methods. Corrosion inhibitors are an alternative to mitigate corrosion, and they act in the modification of the corrosive environment. In recent years, there has been a growing concern about replacing conventional inhibitors with green inhibitors, which have less adverse environmental effects. In this sense, this work proposes to investigate the corrosion inhibition of galvanized steel in 0,5 mol/L hydrochloric acid medium, using avocado seed powder. Avocado seed powder was characterized by Fourier transform infrared spectroscopy (FTIR). The hydroethanolic extract of avocado seed powder was characterized by thin layer chromatography (TLC), hydrogen nuclear magnetic resonance (1H NMR) and high performance liquid chromatography equipped with a sequential mass spectrometry detector (HPLC­MS/MS). The result of these characterizations allowed the identification of compounds and classes of natural products that have in their chemical structure centers responsible for the adsorption of the inhibitor on the metallic surface of galvanized steel. The natural inhibitor was tested through gravimetric and electrochemical tests. The highest inhibition efficiency obtained was 66,51%, in the electrochemical test of electrochemical impedance spectroscopy (EIS), for the avocado seed powder at a concentration of 1,77 g/L. The morphology was also analyzed by scanning electron microscopy (SEM), coupled with an energy dispersive spectroscopy (EDS) system.