Corrosion analysis of renewable inhibitor Citrus aurantifolia peels extract for API 5L Grade B steel in acid solution

An extract from the peels of Citrus aurantifolia (CA) has been investigated as a corrosion inhibitor on API 5L grade B material in acid solution. It was confirmed by FT-IR measurements that the CA peels contained functional groups that could favor corrosion inhibition. The effectiveness of corrosion inhibition was examined through the use of electrochemical techniques and scanning electron microscopy. In 1 M H2SO4, the effectiveness of the inhibitor (200 mg/ L) was 99.2% (from PDP measurements) or 99.1% (from EIS measurement). The Langmuir isotherm model was used to examine the adsorption behavior of the extract. The negative and low Gibbs free energy values supported that the inhibitor was adsorbed on the surface of API 5L Grade B material. This value can also be used as a reference that CA peels extract has a physisorption ability. SEM images show that the surface of the specimen in the presence of the inhibitor forms a thin layer that is thought to be able to inhibit the corrosion rate, whereas on the surface of the specimen in the absence of inhibitor, no thin layer is formed. The results show that under acid corrosion, CA peels extract effectively inhibits the corrosion of API 5L Grade B material because it forms a thin film on the surface of the material.