“…The electrons generated by metal oxidation supported the cathodic reactions (oxygen reduction reactions) on the particle and on the alloy surface at the periphery of the trench. The maximum cathodic region around the pit depended on the number of electrons provided by metal dissolution [25]. Figure 9 Schematic presentation for the evolution of the localised corrosion of AA5083 in simulated seawater.…”
The localised corrosion of aluminium alloy (AA) 5083-H111 in 3.5 wt-% NaCl solution was studied by combing scanning electron microscope (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. It was found that the Ti-rich intermetallic particles (IMPs) served as the cathodes and triggered the dissolution of its adjacent Al matrix; as a result, a trench was formed between the IMP and its surrounding Al matrix. Raised 'circles' were identified on the alloy surface at the periphery of the IMPs, which was considered to be the cathodic region on which corrosion products deposited. A sub-surface that consisted of fine Al grains and corroded Al-Mg phases were observed under the raised 'circle' region.
“…The electrons generated by metal oxidation supported the cathodic reactions (oxygen reduction reactions) on the particle and on the alloy surface at the periphery of the trench. The maximum cathodic region around the pit depended on the number of electrons provided by metal dissolution [25]. Figure 9 Schematic presentation for the evolution of the localised corrosion of AA5083 in simulated seawater.…”
The localised corrosion of aluminium alloy (AA) 5083-H111 in 3.5 wt-% NaCl solution was studied by combing scanning electron microscope (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. It was found that the Ti-rich intermetallic particles (IMPs) served as the cathodes and triggered the dissolution of its adjacent Al matrix; as a result, a trench was formed between the IMP and its surrounding Al matrix. Raised 'circles' were identified on the alloy surface at the periphery of the IMPs, which was considered to be the cathodic region on which corrosion products deposited. A sub-surface that consisted of fine Al grains and corroded Al-Mg phases were observed under the raised 'circle' region.
“…9d, e. First, accumulation of corrosion product within the pit increases ohmic drop between the cathode and anode 47 . Secondly, the migration of Al 3+ and OHions into the droplet Table 1.…”
Section: Discussionmentioning
confidence: 99%
“…The coupling between these factors is complex and is challenging to discern in the experimental data presented in this study. These may be decoupled more readily in modeling studies such as references 47,54,55 .…”
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.
“…50 At atmospheric conditions, the number of water layers residing on the outer surface of the oxide film depends on the humidity but usually exceed a few nanometer in thickness. 51,52 We focus on charge-neutral interfaces with no electric double layers in the electrolyte, and assume that ∼12-18 Å thick pure water films suffice. A system size convergence check is conducted for the lower energy cut of the(110) oxide surface.…”
The surfaces of most metals immersed in aqueous electrolytes have a several-nanometer-thick oxide/hydroxide surface layer. This gives rise to the existence of both metal|oxide and oxide|liquid electrotlyte interfaces, and makes it challenging to correlate atomic length-scale structures with electrochemical properties such the potential-of-zero-charge (PZC). The PZC value has been shown to be correlated to the pitting onset potential for corrosion. In this work, we conduct large-scale Density Functional Theory and ab initio molecular dynamics to calculate the PZC of a Al(111)|gamma-Al(2)O(3)(110)|water double-interface model within the context of aluminum corrosion. By partitioning the multiple interfaces involved into binary components with additive contributions to the overall work function and voltage, we predict the PZC to be -1.53~V vs. SHE for this model. We also calculate the orbital energy levels of defects like oxygen vacancies in the oxide, which are critical parameters in theories associated with pitting corrosion. We predict that the Fermi level at the PZC lies above the impurity defect levels of the oxygen vacancies, which are therefore uncharged at the PZC. From the PZC estimate, we predict the voltage needed to create oxygen vacancies with net postive charges within a flat-band approximation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
