Boyne Smelters is 59.4% owned by Rio and operated by its Alcan division. It is Australia's largest aluminium smelting operation and is located near Gladstone in central coastal Queensland.
The floods have cut road and rail access between Gladstone and Brisbane and the Brisbane port is closed, preventing deliveries to some domestic and international customers.
Rio Tinto Alcan said it was investigating alternative arrangements for customers, including shipping aluminium directly out of the Gladstone port.
Rio Tinto Alcan said it was unable to provide an estimate of the full impact of the disruption to the supply of aluminium from Boyne Smelters Limited or the duration of the force majeure declaration.