Evaluation of the Inhibition Efficiency of a Green Inhibitor on Corrosion of Cu-Ni Alloys in the Marine Application

Abstract

The aim of this article describes the application of green tea aqueous extract as an eco-friendly corrosion inhibitor for two Cu-Ni alloys in 3.5% NaCl solution. This ability has been studied by using electrochemical techniques (i.e. PDP, CT and EIS), IR spectroscopy measurements and the surface analysis technique (i.e. SEM/EDX). This ability was compared with it's of a commercial cooling water (green water). The results show that tested extract exhibited a good ability to decrease the corrosion rate of alloys in 3.5% NaCl solution.The inhibition efficiency of the green water and green tea extract inhibitors increased with increasing the concentration and decreased with increasing the temperature. The inhibition efficiency of two Cu-Ni alloys which reaching ̴ 91.5% and ̴ 93.9% with 50 % green tea aqueous extract for Cu-10 Ni and Cu-30 Ni alloy, respectively. Electrochemical impedance showed that the change in charge transfer resistance (Rct) and double layer capacity (Cdl) which adsorbed on the alloy surface. Adsorption of the inhibitors gives a good fit to Langmuir isotherm model. Some thermodynamic parameters of activation and adsorption processes were also determined and discussed. Surface examination studies by SEM and EDX confirm the presence of protective film on the alloy surface. In the present study, we investigated the corrosion of the Cu-Ni (cupronickel) alloys in 3.5 % NaCl environment to simulate the seawater desalination plants conditions. Therefore, the future studies can be focused on the development of polymeric compounds used as self- healing or production of new natural corrosion inhibitors especially recommended the waste product of green tea.

Corrosion inhibition of two Schiff base complexes on the mild steel in 1M HCl solution

“…The founding of single semi-circle showed the single charge transfer process during dissolution which is unaffected by the existence of inhibitor molecules. Deviations from excellent circular form area unit typically noted the frequency dispersion of surface ohmic resistance that arises because of surface roughness, impurities, dislocations, grain boundaries, sorption of inhibitors, and porous layers formation and in homogenates of the electrode surface [20,23]. The Rct values for the systems containing inhibitors are larger than that of the blank.…”

“…It might be discussed on the basis that the double layer between charged alloy surface and the solution is considered as an electrical capacitor. The decrease in the capacitance might be attributed to the protective layer formation on the alloy surface [20,23].…”

“…The apparent activation energy value, E a , of the blank is larger than the inhibited, however it did not change significantly in the presence of inhibitor, supportive of the proposed chemical adsorption mechanism. Due to reports, activation energy Ea due to chemical adsorption (> 80 KJ/ mol) is considerably larger than because of physical adsorption (< 80 KJ/mol) [20]. The heat of adsorption values Q ads of Cd(II) and UO 2 (II) complexes adsorption on mild steel surface were obtained using Eq.…”

“…Values of heat of adsorption were obtained from the slope (-Q ads / 2.303 R) of a plot of log (θ / 1-θ) against (1/T) for mild steel in concentration of 500 ppm of investigated complexes are shown in Table 8. Obtained values of Q ads are all negative, indicative of exthothemal nature of the dissolution process of mild steel surface in the acidic solution [20]. The apparent enthalpy of activation ∆H ads and entropy of activation ∆S ads values were obtained through the linearized transition -state theory equation given by Eq.…”

“…9, from where values of ∆H ads and ∆S ads were calculated and are existence in Table 8. From Table 8, it is found that the positive values of ∆H reflect that the process of adsorption of the inhibitors on the mild steel surface is an endothermic process; it is shared unequivocally to chemisorption [20].…”