title: The effect of superhydrophobic wetting state on corrosion protection--the AKD example.
abstract: Corrosion is of considerable concern whenever metal is used as construction material. In this study we address whether superhydrophobic coatings could be used as part of an environmentally friendly corrosion-protective system, and specific focus is put on how the wetting regime of a superhydrophobic coating affects corrosion inhibition. Superhydrophobic alkyl ketene dimer (AKD) wax coatings were produced, using different methods resulting in hierarchical structures, where the coatings exhibit the same surface chemistry but different wetting regimes. Contact angle measurements, ESEM, confocal Raman microscopy, open circuit potential and electrochemical impedance spectroscopy were used to evaluate the surfaces. Remarkably high impedance values of 10(10)Ω cm(2) (at 10(-2) Hz) were reached for the sample showing superhydrophobic lotus-like wetting. Simultaneous open circuit potential measurements suggest that the circuit is broken, most likely due to the formation of a thin air layer at the coating-water interface that inhibits ion transport from the electrolyte to the metal substrate. The remaining samples, showing superhydrophobic wetting in the rose state and hydrophobic Wenzel-like wetting, showed less promising corrosion-protective properties. Due to the absence of air films on these surfaces the coatings were penetrated by the electrolyte, which allowed the corrosion reaction to proceed.
authors.affiliation: SP Technical Research Institute of Sweden, Chemistry, Materials and Surfaces, Box 5607, SE-114 86 Stockholm, Sweden; KTH Royal Institute of Technology, Division of Surface and Corrosion Science, SE-10044 Stockholm, Sweden. Electronic address: linamart@kth.se.
authors.forename: Lina
authors.initials: L
authors.lastname: Ejenstam
authors.forename: Louise
authors.initials: L
authors.lastname: Ovaskainen
authors.forename: Irene
authors.initials: I
authors.lastname: Rodriguez-Meizoso
authors.forename: Lars
authors.initials: L
authors.lastname: Wågberg
authors.forename: Jinshan
authors.initials: J
authors.lastname: Pan
authors.forename: Agne
authors.initials: A
authors.lastname: Swerin
authors.forename: Per M
authors.initials: PM
authors.lastname: Claesson
keywords: Alkyl ketene dimer (AKD); Corrosion protection; Superhydrophobic coating; Wetting state