Rollinia occidentalis extract as green corrosion inhibitor for carbon steel in HCl solution

An extract of Rollinia occidentalis as well as pure solutions of two acetogenins isolated from this extract, namely Rolliniastatin-1 and Motrilin, were tested as corrosion inhibitors for carbon steel in acidic solutions. Weight loss measurements were performed in the 298–328 K temperature range and the obtained data were used to calculate corrosion rate and inhibition efficiency. It was found that the extract and the acetogenins solutions act as good corrosion inhibitors for the tested C-steel in 1 M HCl media. Moreover, results from potentiodynamic polarization measurements indicate that R. occidentalis and the two tested acetogenins act as mixed-type inhibitors. Data collected from EIS studies were modeled with an equivalent circuit containing a single time constant what can be understood in terms of a corrosion inhibition process resulting from the geometric blocking effect of the carbon steel surface by an adsorbed inhibitor species. Inhibitor adsorption follows a Langmuir adsorption isotherm. The inhibition efficiency decreases with increasing temperature and extract concentration. Spectroscopic analysis points to the formation of a complex between metal cations and compounds present in the R. occidentalis extract. This additional aspect is considered in the proposed inhibition mechanism of C-steel.