Mining giant Rio Tinto said on Tuesday it will buy Mitsubishi Corp's 11.65% stake in Boyne Smelters (BSL) for an undisclosed sum.

Boyne, which owns and operates the Boyne Island aluminium smelter in Gladstone, Australia, is a joint venture between Rio Tinto, YKK Aluminium and others.

In late May, Rio signed a deal to buy Sumitomo Chemical's 2.46% interest in the venture.

The purchase from Sumitomo Chemical and the completion of the deal with Mitsubishi will see Rio's interest in Boyne increase to 73.5%, the Australian miner said.

"Rio Tinto looks forward to continuing to work with its remaining BSL joint venture partners and other stakeholders on securing a competitive low-carbon future for its Gladstone operations," Rio Tinto said.

The acquisition is set to be finalised in the second half of 2024.

For Mitsubishi, the sale is part of a reshuffle of its aluminium portfolio, and the financial impact - to be booked in the July-September quarter - on its annual earnings forecast will be limited, a company spokesperson said.

The Japanese trading house will no longer hold stakes in any aluminium smelter but will remain active in the aluminium business, including trading and investment in bauxite assets, the spokesperson said. The metal's growth potential is in light-weight automobiles to achieve greater efficiency, they said.

In 2021, Mitsubishi agreed to buy 30% of the Aurukun bauxite project in Australia from Glencore.

(Reporting by John Biju in Bengaluru; Additional reporting by Yuka Obayashi in Tokyo; Editing by Shounak Dasgupta and Christopher Cushing)