Solvent selection and studies of the anti-corrosion efficacy of Heliotropium curassavicum leaves extract on API L X60 steel in 5 wt% hydrochloric acid solution

Corrosion is a huge challenge in the manufacturing industry during sticky oxides, grease, and rust removal from metal surfaces. It is often managed by the use of inhibitors and current interest is on sustainable inhibitors with less to zero harmful effects. This study explores the efficacy of Heliotropium curassavicum leaves extracts (HCLEs) in retarding the deterioration of API X60 grade steel in 5 wt% HCl solution and the influence of extracting solvent namely acetone (ACE), ethanol (ETH), water (WAT), butanol (BUT), methanol (MET), isopropanol (ISO), and ethyl acetate (ETA) on performance. The characterization of the HCLEs was achieved by Fourier-transform infrared (FTIR) and ultraviolet–visible (UV–vis) spectroscopies while the weight loss, electrochemical, and surface examination approaches were used for anticorrosion property evaluation. The results disclose that irrespective of extracting solvent, the extracts could suppress the dissolution of the substrate under the studied conditions. The best performance is, however, noted for ethanolic HCLE where 300 mg/L protected the substrate surface by 51.46% at 25 °C. Hence, ethanolic HCLE was selected for detailed studies and results indicate that the steel surface can be protected by 78.42% if 1000 mg/L of extract is used. Furthermore, the performance of the extract improves upon an increase in the temperature of the corrodent. The findings suggest that ethanolic HCLE could be considered for material protection during HCl pickling.