Evaluation of the Sapindus saponaria L extract as an acid medium corrosion inhibitor

Abstract

Copper and its alloys have characteristics of electrical and thermal conductivity and good toughness. As copper has a positive value for standard reduction potential, it does not react with water, but with oxidizing acids. A useful method to protect metals and alloys is the addition of corrosion inhibiting substances in the solution, which has a high inhibition efficiency.However, many inhibitors are undesirable because of their toxicity to the environment and their high cost. Studies have been developed in order to investigate plant extracts as corrosion inhibitors. The sapindus saponaria L plant may have some technological interest in relation to corrosive processes.For this purpose, the techniques of potentiodynamic polarization of cyclic and linear scanning, chronoamperiometry, gravimetric by mass loss immersion, flame atomic absorption spectrometry and scanning electron microscopy were used. In cyclic voltammetry with the cathodic region extract, there is some interaction with the species in solution. From the polarization curves, linear voltammetry, the efficiency was 63.6%, where the extract behaved as a mixed type inhibitor. Determining the values of the corrosion rate in the absence and in the presence of the extract, the value of 59.8% of inhibitory efficiency in terms of mass loss immersion and 80.0% in terms of copper ions content in solution from flame atomic absorption were found.The micrographic images show that in the presence of the extract, on the copper surface there were no significant changes and the formation of corrosion products did not occur. It is concluded that the extract of sapindus saponaria L is a reasonable inhibitor of copper corrosion in HNO3 1 mol/L.