Development of Sensitisation Resistant 5XXX series Aluminium Alloys

The study of 5xxx aluminium alloys based on the Al-Mg-Mn system, particularly for the prevention and reparation after sensitisation, has gained new attention in the past decade. AA 5083 alloys that exist on more than 200 commercial vessels as well as some navy vessels are reported to be susceptible to intergranular corrosion (IGC). However, compared with the significant efforts put into understanding and quantifying the sensitisation of 5xxx alloys, limited previous research has been performed to develop 5xxx alloys with better inherent resistance to IGC arising from sensitisation. This work will present an exploration towards the development of corrosion and sensitisation resistant 5xxx series. To achieve this, alloying additions of manganese were manipulated in amount, as well as alloying additions of silver, zinc and strontium were added to AA5083(Al-Mg-Mn) at low, medium and high levels, followed by a range of electrochemical tests and characterisation methods. Some major findings were made from the project, including that sensitisation behaviour was found to be largely independent of manganese elemental content over the expected range of its concentration in commercial 5083 alloys, while silver and zinc in small amounts improved nobility.