An agreement has been reached to sell steelmaker and mining group Arrium to GFG Alliance, ending more than a year of uncertainty for the struggling company.

The administrator KordaMentha announced on Wednesday morning that it had signed a binding agreement to sell Arrium to the London-based group, which is owned by the Gupta family from Britain.

KordaMentha said the sale was subject to the approval of the Foreign Investment Review Board, as well as the Arrium Committee of Creditors, which is scheduled to meet next week.

"Subject to those approvals, this is a great result for Arrium employees and the city and people of Whyalla. It ensures their future and ends 15 months of uncertainty," said administrator Mark Mentha.

"Taking all factors into consideration, including the timeframes required to complete a sale, KordaMentha and our sale advisers Morgan Stanley decided that GFG was an option superior to the conditional offer of the Korean alliance with whom we were negotiating," he said.

Mr Mentha also said the sale was a credit to stakeholders who worked extremely hard to give Arrium the chance of a future.

Thousands of jobs in South Australia and all across the country had been in jeopardy since the steel and mining company collapsed and entered voluntary administration last year.

Union officials representing more than 2000 Arrium workers on Wednesday praised the "outstanding credentials" of the company's new owner

Australian Workers Union national secretary Daniel Walton said the announcement was a great day for the town of Whyalla.

"This is the outcome we have been working so hard toward for well over a year," he said. "This is the certainty we wanted to deliver for workers and their families."

Mr Walton said GFG Alliance had an international reputation as a good corporate citizen with a "responsible, long-term vision of success".

"They have invested strongly in heavy industry in Europe and the UK, and it is this mindset they will bring to Australia," he said.

"The Australian steel industry has a bright future, and the GFG Alliance has the track record to realise it."

The sale is still subject to approval, but the South Australian government says it may be completed as early as next month.

Premier Jay Weatherill said the deal signalled the "beginning of the end of the 15 months of uncertainty" for the Whyalla community and "heralded a new future for the state's steel city".