Corrosion resistance of 5052 aluminum alloy using hydrophobic silane coatings

ABSTRACT

The fabrication of silane-based hydrophobic surfaces depends on factors such as organic substitution reactions, the extension of the surface area being covered, and the distribution of hydroxyl groups on the surface area to increase the anchoring of the coating and consequently improve the corrosion resistance of the metal. In this sense, the objective of the present work is to evaluate the corrosion resistance of the 5052 aluminum alloy was evaluated by the development of hydrophobic surfaces using silanes. Nanoparticles (NPTs) of tetraethoxysilane silane (TEOS) were used to provide morphological roughness for the studied substrates. TEOS and vinyltriethoxysilane (VTES) NPTs were combined to verify the synergistic effect occurring when obtaining angles greater than 150°. The fabrication of the TEOS NPT solution was based on propanone and sodium hydroxide, whereas for the mixing of the VTES solution, ethanol, water and acetic acid were used. The silane deposition was carried out using dip coating and electro-assisted techniques. The aluminum substrate with the silane coatings was tested using two variations of surface morphology, as-received (L) and blasted (J). Substrate composition was verified by X-ray fluorescence (XRF). Contact angle (CA) analysis was performed to evaluate the hydrophobicity provided by the coating. The morphology of the substrates was analyzed by TEM (transmission electron microscopy). Corrosion resistance was verified by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results obtained from the VTES coating tests verified that a potential of −1.2 V, combined with the blasted substrate, provided lower wettability. However, the results of the electrochemical tests showed that smooth surfaces with film deposition and potentials of −1.2 V and −0.8 V had more corrosion resistance compared to the other analyzed samples.

Keywords:
Aluminum alloy; Corrosion; Coating; Hydrophobic silanes