Anodização com silanização simultânea: aumento de hidrofobicidade e proteção contra a corrosão em alumínio

In refrigeration systems, aluminum sheets are continually submitted to condensation of water, which provides a corrosive environment and eventually results in the formation of ice and impairment of heat exchange. Therefore, hydrophobic surfaces are highly desirable, in order to extend life and improve performance of refrigeration systems. In this work, we propose a novel anodizing method combining porous anodic oxidation with simultane ous incorporation of hydrophobic organosilanes. Commercially pure aluminum (AA1100) was used as substrate andanodizing baths consisted of different portions of sulfuric acid, water, ethanol and hexadecyl-trimethoxysilane (HDTMS). In some cases, HDTMS hydrolysis was started in controlled environment before anodizing. Anodizing was performed galvanostatically, starting at different temperatures with a current density of 15mA/cm2, for 25 minutes. The anodic layersobtained were characterized by scanning electron microscopy, Raman spectroscopy and fourier transforminfrared spectroscopy (FTIR) and contact angles were measured by the sessile drop technique. The anodic layers obtained are circa 10μm thick with incorporation of silanes inside pores and on the surface, partially blocking the pores. Hydrophobicity was significantly enhanced by adding organosilanes, achieving contact angles greater than 130°. The effects of ethanol concentration, HDTMS concentration and curing process on contact angles werestudied. Corrosion resistance of anodic layers was evaluated using potentiostatic methods and compared to other traditional anodizing methods.