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.

Developing appropriate protecting coatings for Mg alloy applications is a challenging issue. Herein, nanohydroxyapatite (nanoHAP) powder was first fabricated by the simple hydrothermal microwave-assisted method. A direct current electrophoresis deposition (EPD) of nanoHAP composite coatings on Mg–3Zn–0.8Ca magnesium alloy was successfully executed. Three suspensions with HAP-dispersive resin solution (ETELAC) ratios (in wt %) of 5–5, 5–2.5, and 2.5–2.5 were chosen for optimizing the effect of applied voltage, deposition time, and stirring mode and rates on the EPD process. NanoHAP composite coatings were applied on each sample in single- and double-run depositions. The results revealed that the maximum weight gain on the coated samples was obtained in 5–5 suspension at 50 V under 150 rpm mechanical stirring rate. Surface examination indicated crack-free coating formation with varying grain sizes. Adhesion tests demonstrated high interconnection between the obtained nanocomposite coatings and the alloy substrate. Electrochemical evaluation measurements in SBF at 37 °C indicated that the corrosion resistance of any coated sample is always superior compared to that of the uncoated bare substrate. It was suggested that the EPD of nanoHAP/ETELAC composite coatings on Mg–Zn–Ca alloy can be a good solution for protecting the alloy from the attack of the aggressive ions bound in the SBF environment.

The superhydrophobic surface (SHS) is the surface with a high apparent contact angle (> 150 °), low hysteresis in the contact angle (< 10 °), and low sliding angle. Owing to many applications of SHS (such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces, etc.), the artificial SHS could be prepared. This review article focuses on the deposition, behaviour and application of the SHS. It includes an introduction, fundamental principles of superhydrophobicity, main factors for SHS fabrications, deposition methods used to prepare the SHS, and factors affecting the electrochemical synthesis of electroconducting polymers. Moreover, the mechanism of the electrochemical synthesis of polymers, applications of SHS in different fields, and the stability of SHS have been presented. Finally, the challenges of SHS have been discussed.