PSI - Issue 42

Christina Margaraita Charalampidou et al. / Procedia Structural Integrity 42 (2022) 1708–1713 Charalampidou et al./ Structural Integrity Procedia 00 (0000) 000 – 000

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specimens, while solution temperature was 25 ± 1  C. More details can be found in the respective standards. The specimens were cleaned with alcohol prior to corrosion exposure according to ASTM G1 standard. Additionally, they were masked with appropriate insulating PVC tape to be exposed only at the reduced surface area of approximate 55 mm in length. The experimental procedure was carried out in laboratory environmental conditions and at room temperature. The corroded specimens were immediately cleaned according to ASTM G1 standard after the corrosion exposure, and then were subjected to tensile mechanical testing. 2.2.2 Macroscopical examination After the immersion of the specimens to the various corrosive environments and prior to tensile testing, corroded specimens were examined in a KERN ® OZP 558 stereo zoom microscope to reveal the surface corrosion damage. The upper and down flat surfaces of the tensile specimens were examined. 2.2.3 Tensile tests After the immersion of tensile specimens for several exposure times to different corrosive environments, tensile tests were conducted. Tensile tests were carried out in a servo hydraulic Instron 100 kN testing machine according to ASTM E8 standard. Crosshead displacement rate was kept constant and equal to 0.7 mm/min. An external Instron extensometer with 50 mm ± 10 mm maximum travel was attached to the reduced cross-section gauge length of the specimens. A data logger was used during all tensile tests and the values of load, displacement and axial strain were recorded and stored in a computer. More than three specimens were tested in each different case to get reliable average data. Exposure of aluminum alloy 2198-T8 specimens to corrosive solutions leads to surface deterioration due to nucleation of corrosion-induced surface pits, as can be seen in Fig. 1. No significant difference on the morphology of corroded surfaces was noticed for the specimens exposed for different times to EXCO solution, e.g., Fig. 1a. Nevertheless, signs of exfoliation are evident after 48 h of exposure. Pitting corrosion was found to be uniformly distributed to the whole specimen’s surface for all exposure times to EXCO solution. On the contrary, essential difference in pitting density and / or size was noticed on Fig. 1b and Fig. 1c with increasing exposure time for the specimens exposed to NaCl and Harrison’s solutions , respectively. Nevertheless , specimens exposed to Harrison’s solution exhibited severe localized corrosion, while this was not the case for the specimens exposed to NaCl solution. 3. Results and discussion 3.1 Macroscopical analysis

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(c) Fig. 1: Typical photographs of pre-corroded tensile specimens of AA2198-T8 exposed to three different corrosive solutions.