الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 175 |  |  |
| | | from | 175 | | |
Abstract
Surface active agents are considered as important compounds which have important applications in various industrial fields. In addition to participate in the formulation of emulsions and phase transfer catalysis, surface active agents are used as corrosion inhibitors for different metals in the corrosive media. As a result of the integrated usage of the surface active agents in several industrial fields, their improvement was urgent to synthesize new types which characterized by higher efficiency in their applications and also to decrease the used dose.
The unique improvement of the surface active agents was introducing Schiff base groups in their skeleton to improve their adsorption at the different surfaces. That increased their efficiency as corrosion inhibitors.
Also, Gemini surfactants need to be symmetrically disposed about the center of the spacer can self-assemble at much lower concentrations and are superior in the surface activity as compared to conventional surfactants. These surfactants have very low critical micelle concentration (CMC) and have high solubilizing capacity than the corresponding conventional surfactants. The adsorption mechanism of Gemini surfactants on steel surface is quite different and more complicated from that of conventional single chained surfactants. Like conventional surfactants, in case of Gemini surfactants also multilayer may form at surfactant concentration above CMC.
In this work, four Schiff bases Gemini surfactants were synthesized acting as surface active agents. The chemical structures of the synthesized compounds were confirmed using elemental analysis, infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) spectroscopy. The surface activity of the synthesized compounds was investigated and showed good surface activity in their solution. The prepared compounds were evaluated as corrosion inhibitors for carbon steel in acidic medium using different tools: weight loss, electrochemical polarization and electrochemical impedance techniques.
The results of the corrosion inhibition measurements revealed that:
1. The inhibition efficiencies of the different inhibitors were increased by increasing the hydrophobic chain spacer of the Gemini cationic surfactants.
2. The presence of the heteroatoms in the rings increases the inhibition efficiencies considerably.
3. Increasing the number of positive charge in the synthesized molecule (+N) increasing the adsorption on the surface of steel and consequently increases the inhibition efficiencies.
4. Calculation of the free energy of the corrosion processes showed that the corrosion inhibitors are attached to the metal surface physically. The negative values of the free energy of adsorption of the inhibitor molecules on the metal surface indicate that their adsorption is spontaneous.
5. The electrochemical polarization and impedance techniques were confirmed the inhibition efficiencies data which prove the validity of the data obtained from two different tools.