Study of the anticorrosive properties on SAE 1010 steel of rosemary (Rosmarinus officinalis), laurel (Laurus nobilis) and false incense (Plectranthus coleoides)

The leaves of perennials plants Rosmarinus officinalis, Laurus nobilis and Plectranthus coleoides have a large number of chemical compounds that contain heteroatoms in their structure. This type of heterocompounds has been reported to have chemical affinity for metal surfaces. This work presents the obtaining, characterization and study of the anticorrosive performance on SAE 1010 steel of the aqueous extracts of the aforementioned perennials plants. The plant species were cultivated and harvested in the Greater La Plata area, Province of Buenos Aires, Argentine Republic. The preparation of the aqueous extracts was carried out using the maceration technique. The solid residue of the aqueous extracts was characterized by Fourier transform infrared spectroscopy (FTIR). Electrochemical evaluation was accomplished by linear polarization tests. The anticorrosive performance was determined by exposing SAE 1010 steel samples for 24 h to a corrosive medium in the presence of each of the extracts, and the subsequent analysis of the surfaces obtained through scanning electron microscopy (SEM) and X-ray scattering spectroscopy (EDX). The results were compared with those obtained using zinc aluminum polyphosphate hydrate (ZAPP), a commercial anticorrosive pigment. The results obtained allow us to conclude that the extracts of the three plants inhibit the corrosion of SAE 1010 steel in a manner comparable to that carried out by ZAPP, with the extract of Plectranthus coleoides being the one that presents the best anticorrosive action.