Photo-corrosion of an anodized titanium surface in 0.05 mol dm −3 sulfuric acid solution was investigated by using an in situ electrochemical ellipso-microscope. Irradiation of ultra-violet (UV) light on an anodized surface, which showed a patch-like bright image on an ellipso-microscopic view due to non-uniform growth of the oxide film, under potentiostatic polarization allowed the flow of a photo-induced anodic current and changed the brightness and patch pattern in the image. This indicates that the irradiation promotes photo-electrochemical reaction, resulting in a change in the thickness and/or structure of the oxide film on the surface. The film change was dependent not only on power density of the irradiation light but also on applied potential during the irradiation and crystallographic orientation of the substrate. Pitting initiation during potentiodynamic polarization in the acid with bromide ions was also monitored using the ellipso-microscope. The irradiation resulted in pitting initiation at lower potentials than those in a non-irradiated condition.
The photo-reaction of halogen-substituted anthraquinones in sulfuric acid was studied with near UV or visible light. α-Chloro-substituted anthraquinones were photo-hydroxylated mainly to form α-hydroxyanthraquinones in fairly good yields. However, β-halogenoanthraquinones gave no dehalogenated products under the same conditions.
Die Photo‐Reaktion der α‐Chloranthrachinone (I) in konz. H2SO4 führt zu einem Gemisch aus den 1‐Hydroxyanthrachinonen (II) und den Chlorhydroxyanthrachinonen (III).
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