Electrochemical and anticorrosion properties of 5-hydroxytryptophan on mild steel in a simulated well-acidizing fluid

Peer review under responsibility of Taibah University.

Abstract

The anticorrosion effect of 5-hydroxytryptophan (5-HTP) on mild steel (MS) was investigated by gravimetric and electrochemical techniques. Two different concentrations (1 M and 15%) of hydrochloric acid were used to simulate well-acidizing fluid. The results show that 10 × 10⁻⁵ M 5-HTP is 96.1% efficient in 1 M HCl and 78.1% efficient in 15% HCl at 30 °C. The efficiency decreases as the temperature increases, reaching 66.9% and 39.8% in 1 M and 15% HCl, respectively, at 90 °C. When 5-HTP is blended with potassium iodide and glutathione, the efficiency increases to above 88% and 78% in 1 M and 15% HCl, respectively, at 90 °C. Increasing the 5-HTP concentration decreases the double-layer capacitance and increases the charge-transfer resistance. 5-HTP behaves as a mixed‐type corrosion inhibitor with anodic predominance and is spontaneously adsorbed on the steel surface. Physisorption of 5-HTP is best described by the Langmuir adsorption model and is also exothermic with a resultant decrease in the entropy of the bulk solution. The results of SEM/EDAX, FTIR and UV–VIS studies support the hypothesis that a protective film of 5-HTP forms on MS facilitated by O, N and C=C functionalities.

Keywords:

• 5-Hydroxytryptophan
• Well acidizing
• Corrosion inhibitor
• EIS
• SEM/EDAX
• Acid corrosion

Acknowledgements

The authors acknowledge support from the World Bank through the Robert S. McNamara Fellowship programme to conduct laboratory work abroad. We also acknowledge Dr. Shuangqin Sun and the entire Corrosion Protection research group of the Materials Physics and Chemistry Department, China University of Petroleum Qingdao for providing the facilities for carrying out this research. We appreciate the African Centre of Excellence (ACE), Centre for Oilfield Chemicals Research (CEFOR) for their support. EI is grateful to Prof A. P. Udoh, Dr. Li, Dr. Wang, Ubong Jerome, Chen, Chao, Xiang and Min in UPC for their assistance.

Notes

Peer review under responsibility of Taibah University.