Theoretical investigation of the effect of some inhibitors on the corrosion of al (2024) alloy used in the aviation sector

In the aviation industry, corrosion is a very important form of damage. It causes excessive fatigue of materials used in aircraft, decreases life and productivity. This situation also affects the service life and maintenance intervals of the vehicle. Manufacturers operating in the aviation industry, prefer corrosion-resistant materials during material selection. Furthermore, with the addition of inhibitors which reduce the corrosion rate when added to the environment in a certain amount to delay the formation of corrosion, more cost-effective materials can be used instead of using durable but high-cost materials. Aluminum alloys are a good choice for aircraft wings and various construction materials. Performance properties, cost, design and manufacturing techniques are the reasons for the use of significant amounts of aluminum alloys for the new generation of aircraft. Al (2024) alloy plates have good fracture toughness and fatigue properties. They are also preferred for aviation applications because they have higher damage tolerance and longer durability. In this study, the effects of Na2CrO4, CeCl3, SrCrO4, C7H5NaO2 inhibitors were examined theoretically by Density Functional Theory-DFT method for corrosion of Al (2024) alloy, which is widely used in aviation sector, due to various conditions occurring with time. Electronic structure calculations and visualization were performed with the help of Gaussian 09 program. These calculations were carried out separately in the gas and aqueous phases for the states of both neutral compounds and in the presence of NaCl that simulates a corrosive environment. The optimization was performed using the B3LYP function and SDD basis set. In order to understand the electronic structure, quantum chemical parameters such as EHOMO, ELUMO, ΔE, dipole moment (μ), electronegativity (χ), spherical hardness (𝜂), and electrophilicity index (ω) were calculated. In addition, the experimental data including corrosion rate and polarization resistance (Rp) referred to in this thesis study belong to a previous experimental study on Al (2024) alloy, which is corroded in 0.1 M NaCl environment. When the theoretical calculations and experimental results are compared, it is concluded that there is no direct correlation between the inhibition properties and the electronic structure parameters for the neutral states of the compounds, but in the presence of a NaCl compound, it is found that the theoretical data obtained in the presence of a NaCl compound for the best inhibitor Na2CrO4 are related closely with EHOMO and ΔE parameters.