Ultrahydrophobic aluminium surfaces: properties and EIS measurements of different oxidic and thin-film coated states

Firstly, the contribution summarises important results of the work dedicated to the formation of ultrahydrophobic aluminium surfaces. This treatment comprises sulphuric acid anodisation under intensified temperature and current density conditions ('SAAi') as well as subsequent chemical modification ('C'). The usual sulphuric acid anodisation ('SAAu') was included for comparison. These various states were examined by electrochemical impedance spectrometry (EIS) to derive typical EIS-related features, especially for the ultrahydrophobic states compared to the anodised surfaces. Based on well-defined spectra types, modelling yielded results, preferentially with regard to the nano-porosity of the oxidic layers. EIS measurements allowed the conclusion that the original nano-porosity underwent specific changes due to the chemical modification variants employed. The chances of EIS predicting the stability of the ultrahydrophobically modified systems are critically assessed on the background of standardised weathering tests.