The $345-million offer also includes Rio Tinto’s 53% share in Dutch anode facility Aluminium & Chemie Rotterdam BV (Aluchemie), and 50% of the shares in Swedish aluminium fluoride plant Alufluor AB.

The transaction is expected to be finalized in the second quarter of 2018, subject to successful consultations with Rio Tinto employees and other stakeholders, and approval from European Union competition authorities.

"The bid demonstrates our strong belief in aluminium, which is seeing the strongest global demand growth among base metals. Having presence across the value chain is essential to create value from this growth and promote sustainable practices in our global operations," Svein Richard Brandtzæg, Hydro’s president and chief executive officer (CEO), said.

Isal produces approximately 210,000 tonnes per year of liquid primary aluminium and 230,000 tpy of extrusion ingot for the European building, construction and transportation segments.

“[The acquisition] will further strengthen Hydro's position as the preferred and leading extrusion ingot supplier in Europe,” Hydro said.

The purchase will increase Hydro’s total primary aluminium production capacity to 2.4 million tonnes in 2018 and its share of production that is based on renewable energy to over 70%, the company said.

Hydro also sees synergies with respect to technology, optimization of its anode portfolio, and freight and handling.

"We see great potential in exchanging competence and technology elements between our aluminium plants. We are now running a technology pilot in Norway which aims to be the world's most energy-efficient and climate friendly aluminium production facility. These innovations will be expanded to other Hydro facilities, and as part of Hydro, Isal will benefit from such technological spin-offs and competence," Hilde Merete Aasheim, head of Hydro's primary metal business area, said.

Isal runs on the same technology platform as Hydro's Husnes plant in Norway.

Aluchemie, currently 53.3%-owned by Rio Tinto and 46.7%-owned by Hydro, is an anode production facility in Rotterdam in the Netherlands. It produces around 340,000 tpy of anodes.

Alufluor produces high-purity aluminium fluoride - which is used in the primary aluminium process - in Helsingborg, Sweden. It is currently 50% owned by Rio Tinto and 50% by Yara International.

"The binding offer for the sale of these assets provides further evidence of Rio Tinto's commitment to strengthen our business and deliver value by streamlining our portfolio,” Alf Barrios, Rio Tinto aluminium chief executive, said.

Rio Tinto, under CEO Jean-Sebastien Jacques, has been looking to streamline its portfolio and retain only its best-performing units. Liberty House recently made a binding conditional offer of $500 million to acquire Rio Tinto’s Dunkerque aluminium smelter in northern France, the largest smelter in Europe.

Other than Isal, other assets for sale include the Anglo-Australian’s Pacific Aluminium portfolio in Australia and New Zealand, Metal Bulletin understands.