High purity iron and commercial Type 304 and 430 stainless steels were anodized in ethylene glycol electrolytes containing fluoride and water. When iron was anodized in the electrolytes containing relatively high water concentrations (≥1.5 mol dm−3) at 50 V, porous anodic films with scalloped metal/film interface were developed. In contrast, the anodic films formed in the electrolytes with low water concentrations (≤0.5 mol dm−3) resulted in the flat metal/film interface. In addition, the interpore distance became smaller with respect to the thickness of barrier layer when the water concentration is reduced. These morphological changes may be associated with the change in the composition of the anodic films. Anodizing of stainless steels was dependent upon the type of stainless steel; a steady-state current continued up to ~160 V on Type 430 stainless steel, while exponential current increase occurred above ~50 V on Type 304 stainless steel during potentiodynamic anodizing. The thickness of the barrier layer and the morphology of the porous layer were largely dependent upon the type of stainless steel. Based on such findings, the mechanism of film growth was discussed.

Highlights ・The CeO-coating is formed on Type 304 stainless steel by anodic deposition. ・The hydrophilic CeO 2 surface is transformed to hydrophobic during air exposure. ・Superhydrophobic CeO 2 surface is obtained on hierarchically rough substrate. ・Superhydrophobic CeO 2 surface shows self-healing property.

Effects of an inhibitor on the corrosion of Al and Al alloys in Cl and Cu 2 solutions at 363 K have been investigated by gravimetr y and analyses of surfaces and vertical cross sections of specimens with a scanning electron microscope and an energy dispersive X-ray spectrometer. Addition of the inhibitor to the Cu 2 solution inhibited effectively the corrosion of Al and Al alloys, while inhibitor addition to the Cl solution didnt at all. The inhibitive effect in the Cu 2 solution can be explained in terms of the SiO 2 film formation on the specimen, leading to the suppression of Cu deposition.

Corrosion of A1050-, 3003-and 4043-Al alloys has been investigated by dry-wet repeating tests with droplets of NaCl solution and pure water at 323 K, and compared with that obtained by immersion tests. Scanning electron microscopy and energy dispersive X-ray spectrometry showed that 50 -100 μm-size pits are formed at edge areas of NaCl -droplet, while a local dissolution of Al occurs around Fe-Al-intermetallic compound phase and Si-phase at central regions of the droplets, being similar to the behavior during immersion tests in a NaCl solution. In the case of pure-water dry-wet repeating atmospheres, needle like crystalline hydroxide films are formed at edge areas of pure water-droplets, while thin amorphous hydroxide films are formed at the central regions.Key words : aluminum alloys, corrosion, Cl -ion, pure water, Dry-Wet-Cycle test