Vol.:(0123456789) 1 3 J Bio Tribo Corros (2017) 3:54 DOI 10.1007/s40735-017-0115-y Corrosion Inhibitive Behavior and Adsorption of Millet (Panicum miliaceum) Starch on Mild Steel in Hydrochloric Acid Environment S. C. Nwanonenyi 1  · I. O. Arukalam 1  · H. C. Obasi 1  · U. L. Ezeamaku 1  · I. O. Eze 1  · I. C. Chukwujike 2  · M. A. Chidiebere 3,4   Received: 11 April 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 © Springer International Publishing AG 2017 Keywords Corrosion · Mild steel · Inhibition eiciency · Mathematical simulation technique 1 Introduction Steel and its alloys are advantageously employed in various applications ranging from structural, industrial (chemical, petrochemical, metallurgical), automotive to domestic appli- cations. These wide range of applications are attributable to some speciic properties of steel and alloys [1] which include high thermal, mechanical strength, conductivity, electrical properties, and cost efectiveness. However, mild steel for instance gradually fails to display these speciic properties optimally on exposure to aggressive service environment for a longer range of time due to the resultant corrosion efect. Hence, during corrosion process (acid or alkaline induced), steel and alloys degrade or deteriorate because of reactions with the surrounding environment. Some typical applica- tions where acid solutions meet metals include textile dye- ing, automobile batteries, coolants and cleaners, water treat- ment, cleaning of oil and gas pipelines, oil and water drilling operations, fruit and juice processing plants. The resultant efects of exposing metals to harsh service environment lead to failures of mechanical or physical properties, injuries to human beings and the environment, cost and material loss. Hence, it is practicable using diferent inhibitors to control or reduce these efects of corrosion on metals. Starch (bio-polymer) is a viable alternative and reliable source of inhibitors for controlling unhealthy efects of exposing metals and their alloys to the aggressive environ- ment during service or maintenance. This behavior is likely because its molecular and structural constituents serve as media through which electrons transfer occurs between the inhibitor and surface charges on the metal thereby leading Abstract The performance of millet starch (MS) in controlling the corrosion of mild steel in 0.5 M HCl solu- tion at 30 ± 1 °C was investigated using potentiodynamic polarization, gravimetric, thermometric and mathematical simulation technique. Data obtained from gravimetric and thermometric results revealed that MS inhibited corrosion of mild steel in the acid solution and increase in inhibition eiciency was concentration dependent for all the concentra- tions of MS investigated. The mode of adsorption of MS on the mild steel surface obeyed Langmuir adsorption isotherm. The potentiodynamic polarization result indicates that MS act as a mixed type inhibitor with absolute control on the cathodic partial reaction. The thermodynamic parameters (∆H ads , ∆S ads , ∆G ads and E a ) for the inhibition process were calculated, and the results obtained supported the proposed physical adsorption mechanism. The mathematical simula- tion technique was used to evaluate the correlation between the inhibition eiciency of MS and its electronic molecu- lar structure. The results show that there is a satisfactory agreement between mathematical simulation technique and experimental data. * S. C. Nwanonenyi simeonnwanonenyi@gmail.com 1 Department of Polymer and Textile Engineering, Federal University of Technology, Owerri, Nigeria 2 Department of Polymer and Textile Engineering, Nnamdi Azikiwe University, Awka, Nigeria 3 Electrochemistry and Materials Science Research Laboratory, Department of Chemistry, Federal University of Technology, Owerri, Nigeria 4 Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China