The evolution of pit morphology and growth kinetics in aluminum during atmospheric corrosion

Abstract

Assessing the lifetimes of alloys in humid, corrosive environments requires growth kinetic information regarding individual instances of damage, e.g. pit growth rates. Corrosion rates measured at the continuum scale using mass change convolute the rate of pit nucleation and growth, providing limited information on local kinetics. The current study used in-situ X-ray computed tomography to measure growth rates of individual pits in aluminum over 100 h of exposure in a humid, chloride environment. While pits grew at relatively constant rates over the first hours after nucleation, significant growth-rate nonlinearities subsequently occurred. These were linked to both droplet spreading, which altered the cathode size, and changes in the mode of pit growth. Pit morphology appeared to influence the dominant growth mode and the duration of pit growth. Post-mortem serial sectioning revealed pits preferentially attacked grain-boundary triple junctions and dislocation boundaries.

Fracture Behaviour of Aluminium Alloys under Coastal Environmental Conditions: A Review

“…This layer consists of metal oxides and can act as a barrier, preventing further corrosion by isolating the metal from the surrounding environment. Pits are small, localised cavities that form on the surface of a material due to exposure to a NaCl solution [89]. They are typically deeper than they are wide and can penetrate the material, compromising its integrity.…”

“…This leads to the formation of cracks and corrosion products, which decreases corrosion resistance, as shown in Figure 9. Corrosion Pits are small, localised cavities that form on the surface of a material due to exposure to a NaCl solution [89]. They are typically deeper than they are wide and can penetrate the material, compromising its integrity.…”