Evaluation of corrosion of 5052 aluminum alloy using superhydrophobic coatings based on stearic acid

ABSTRACT The hydrophobicity of a surface gives it peculiar properties, making it non-sticky and more resistant to corrosion. Stearic acid (SA) is saturated carboxylic acid that has C18 in molecular structure. The longer the carbon chains of fatty acids in a coating, the lower its solubility in water and consequently the greater its superhydrophobic characteristic. This study is of fundamental importance because it presents the potential for technology transfer since the methods used in this study, both for manufacturing and deposition of coatings, are simple and can be applied industrially, and also use low-cost products such as SA. In this sense, the objective of this study is to evaluate the corrosion resistance of the 5052 aluminum alloy when coated with superhydrophobic films based on stearic acid. Stearic acid (SA) in a 1% ethanolic solution was deposited using dip-coating. Aluminum substrate coated with SA was tested with three variations of surface morphology: as received (L), sanded (#) and sandblasted (J). The morphology of the substrates was analyzed by scanning electron microscopy (SEM), and the chemical composition of the coating/substrates, by energy dispersive spectroscopy (EDS). Contact angle (CA) analysis was performed to verify the hydrophobicity provided by the coating. Corrosion resistance was assessed using electrochemical impedance spectroscopy (EIS) and salt spray testing. The blasted surface yielded the best contact angles, with a mean angle of 158.9°. The superhydrophobic sample showed better corrosion resistance than the other substrates, which had contact angles below 150°.