In order to test the applicability of 8090-T81 alloy in a marine environment, its corrosion behaviour was investigated in natural sea water at 25 deg C. Corrosion resistance was examined using free corrosion and electrochemical tests. The surface film was characterised by IR spectroscopy, X-ray microdiffractometry, and X-ray photoelectron spectroscopy. Microstructural heterogeneity increases susceptibility to localised attack, particularly to crevice corrosion, thus discouraging any marine use of this alloy in a non-protected form. The corrosion resistance of 8090-T81 alloy in sea water does not appear to match the favourable physical and mechanical properties of this innovative material. In fact, potentiodynamic anodic polarisation tests show that the Al-Li alloy in a T81 state could suffer pitting corrosion, since its perfect passivity domain (ca. 25 mV) and its selfrepair domain (ca. 50 mV) are very small. Free corrosion experiments show that 8090-T81 alloy held in sea water under conditions of varying degrees of dissolved oxygen content (owing to voids, fissures, shielding phenomena, etc.) suffers crevice corrosion, enhanced by the presence of copper in the bare alloy. Metallic copper coming from the desmutting reaction of Cu(+) ions, also precipitates on metallic surfaces thus creating microgalvanic cells and favouring crevice corrosion attack. Selective lithium dissolution takes place in the alloy: the Li/Al ratio between lithium and aluminium as soluble corrosion products is higher than that of the ratio between lithium and aluminium in the metal.
Corrosion behaviour of aluminium-lithium alloy 8090-T81 in sea water
Korrosionsverhalten der Aluminium-Lithium-Legierung 8090-T81 in Meerwasser
British Corrosion Journal ; 30 , 3 ; 227-231
1995
5 Seiten, 10 Bilder, 31 Quellen
Aufsatz (Zeitschrift)
Englisch
Korrosionsprüfung , potentiostatische Prüfung , Meerwasser , Spaltkorrosion , Lochfraßkorrosion , Korrosionsstrom , Korrosionsprodukt , Aluminiumlithiumlegierung , Wärmebehandlung (Materialbearbeitung) , Passivierung , elektrochemische Korrosion , chemische Zusammensetzung , Konzentration , Ablagerung , Sauerstoffgehalt , selektive Korrosion
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