Abstract
Anodizing and deposition of hydrophobic films are processes used separately to improve the atmospheric corrosion resistance and hydrophobicity of Al alloys used for heat exchangers. In the present work, we assessed the effect of various additives on the sulfuric acid anodizing (SAA) electrolyte, namely ethanol, trifluoroethanol, hexadecyltrimethoxysilane (HDTMS), and perfluorooctyltriethoxysilane (PFOTES). By tailoring the anodizing process, simultaneous growth of a protective porous layer and hydrophobicity increase of AA1100 were achieved in one step. Cell potential transients and XPS surface analysis confirm that silane incorporation into the oxide structure during anodizing enhances the hydrophobic properties of samples anodized in SAA-ethanolic PFOTES electrolytes. When HDTMS is added, a uniform hydrophobic protective coating is produced, but the electrolyte is unstable. The time required for nucleation of pitting corrosion in potentiostatic tests in NaCl increases when ethanol, HDTMS, or PFOTES are incorporated in the anodization bath.
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