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A combination of quartz crystal microweighing (QCM) and infrared reflection absorption spectroscopy (IRRAS) was used to investigate the formation of ultrathin polysiloxane films on iron oxide surfaces by the adsorption of alkyltrimethoxysilanes in a humid atmosphere. It was shown that in the absence of a catalyst, only the most reactive methyltrimethoxysilane led to film formation. These films are not completely polymerized and incorporate silanols and water. The addition of n-propylamine to the reactive gas phase as an alkaline catalyst enables one to use even the butyltrimethoxysilane as a starting material and leads to a much higher deposition rate. In addition, these films are completely condensed and very hydrophobic. Layers of both alkoxysilanes even with a thickness corresponding to only a few monolayers showed high stability in the presence of a corrosive atmosphere (SO2, H2O, O2), leading to significant inhibition of the corrosion process. Corrosion started at local defects in the film, whereas t...

Combinatorial material development was combined with high throughput microelectrochemistry to allow an efficient but comprehensive investigation of the interface chemistry of Al rich Al–Fe alloys as a function of their chemical composition. Composition spread thin films with a linear composition gradient were produced by thermal codeposition. A scanning droplet cell was used to determine the open circuit potential and to perform successive anodic oxide formation with intermittent impedance spectroscopy. The film formation factor, the relative permittivity of the oxides and the onset potential of oxide formation were determined quantitatively as function of the composition with a resolution of 0.5 at.%. An unexpected synergistic effect is found in a very narrow composition range between 9 and 12 at.% Fe. This effect, which shifts the onset potential by nearly 1 V, is discussed in terms of a local accumulation of Fe resulting in a redox stabilisation of space charge layer formation during high-field oxide growth. The results are supported by composition and depth dependent XPS measurements.