Abstract
The present work investigates the influence of temperature on C38 steel corrosion in a 1 M HCl medium with and without different concentrations of a hydro-alcoholic extract of used coffee grounds (HECG). The potentiodynamic polarization technique and the electrochemical impedance spectroscopy were performed in temperatures ranging from 293.15 to 323.15 K. It was observed that the inhibition efficiency decreased with increased temperature and inhibitor concentration. The HECG adsorption process on C38 steel surface was found to be spontaneous and obeyed to Langmuir isotherm at all studied temperatures. The associated thermodynamic parameters of adsorption led to suggest the occurrence of physical adsorption of the HECG compounds on the C38 steel surface.
Highlights
Corrosion inhibitors remain an original method to protect metals and their alloys against corrosion processes in corrosive environment [1, 2]. ese are essentially organic molecules containing sulfur, oxygen, nitrogen, and phosphor. e inhibiting action of such compounds is mainly attributed to their adsorption on the metal surface [3, 4]
It is a blend of Arabica and Robusta coffees; which are the two most commonly consumed varieties of coffee in the world [12]. e used coffee grounds were put in the oven at 40°C in order to avoid any alteration during storage and for drying
Tests were performed under varying temperatures from 293.15 to 323.15 K in 1 M HCl medium with and without different concentrations of the hydro-alcoholic extract of used coffee grounds (HECG) a er 30 min of immersion, in order to obtain a steady-state of the open circuit potential (EOCP)
Summary
Corrosion inhibitors remain an original method to protect metals and their alloys against corrosion processes in corrosive environment [1, 2]. ese are essentially organic molecules containing sulfur, oxygen, nitrogen, and phosphor. e inhibiting action of such compounds is mainly attributed to their adsorption on the metal surface [3, 4]. Based on the literature, used coffee grounds are rich in dietary fiber, protein, essential amino acids, and sugar [9]. This waste is le with no apparent value in the industrial sector [10]. For these reasons, the use of this residue for metals protection against corrosion is an interesting ecofriendly solution. Several studies have investigated the effect of temperature on the inhibition of steel corrosion in acidic environments in the presence of green inhibitors [16, 17].
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