In situ X-ray tomography of intergranular corrosion of 2024 and 7050 aluminium alloys

Operando Observation of Galvanic Corrosion Between Aluminum Alloy 7050-T7451 and 304 Stainless Steel in a Simulated Fastener Arrangement Using X-Ray Tomography

“…[18][19][20] It has previously been used to study the 3D nature of initiation and propagation of IGC under droplets and has been used to study localized corrosion and the transition to SCC. [20][21][22] XCT has also been used to study the role of second-phase particles in corrosion initiation of AA6016 (UNS A96016) and found corrosion propagation to be independent of grain boundaries and second-phase particles. 23 However, this technique has not been used to provide operando information on the galvanic coupling of dissimilar metals, especially hidden corrosion damage inside a model fastener arrangement, which normally could not be assessed until the end of an exposure.…”

The effect of droplet size on the localized corrosion of high‐strength aluminum alloys

“…Corrosion was found to initiate discretely all over the surface and was not confined to a central anodic region as is suggested by the classical Evans droplet model. It is agreed here that the initiation of corrosion depends on the microstructure such as the arrangement of constituent particles into clusters. This would explain why corrosion initiates near the extremities of the droplet, in a region that the Evans droplet model would suggest to be predominantly cathodic due to the reduction of oxygen.…”

“…The Evans model , which was largely developed for steels and zinc , assumes that the oxygen concentration is greatest at the extremities of the droplet, which establishes as a relatively more cathodic region compared with the center of the hemispherical droplet, which is relatively more anodic. This separation of anodes and cathodes also occurs in passive metals such as aluminum ; however, complications arise because corrosion initiation maybe more dependent on microstructural features such as clusters of intermetallic particles . Furthermore, the Evans model is applicable to relatively large droplets where oxygen depletion in the center of the droplet can occur but was not applicable to relatively smaller droplets or thin layers of moisture where oxygen depletion does not occur .…”

Self-Healing Effect of Hybrid Sol-Gel Coatings Based on GPTMS, TEOS, SiO2Nanoparticles and Ce(NO3)3Applied on Aluminum Alloy 7075-T6

“…It is known that the deposition of Ce-oxides proceeds at the cathodic sites at the surface which are, in the case of AA7075-T6, Cu-containing intermetallic particles (IMPs). [54][55][56][57][58][59] The fact that no Cu could be identified at the intermetallic particles proves that the deposits of Ce hydroxide/oxide are thicker than is the EDS analysis depth, i.e. several micrometers.…”