Corrosion of Al-Alloys during Dry/Wet-Repeating Atmospheres with Pure Water and NaCl Solution

Abstract

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.