Workers at South32's Worsley Alumina refinery in Western Australia began a 48-hour stoppage on 10 November, turning the planned transfer of the asset to Alcoa into a test of how existing pay and working conditions will be carried across an ownership change. Around 200 union members are employed at the operation, according to AMWU state secretary Steve McCartney. The action involves the Electrical Trades Union and the Australian Manufacturing Workers' Union and coincides with a scheduled shutdown at the refinery's main processing plant.
A dispute over guarantees, not increases
The stoppage is focused on remuneration security rather than a demand for higher pay, according to McCartney. Worsley workers have received an average bonus of 10 per cent over the past five years, and the union wants short-term incentive payments secured through the enterprise agreement. The union says South32 has referred to incentive payments when discussing employees' overall remuneration but has not provided a binding guarantee to protect those earnings.
That gap between a policy commitment and an enterprise-agreement guarantee is the core of the dispute. South32 says its existing short-term incentive policy will continue after the transaction is completed, and that Worsley employees receive benefits beyond their base wages. The union is seeking a binding commitment through the enterprise agreement, while South32 points to the continuation of its policy. McCartney said the request was for continuation of benefits workers had consistently received, not an increase.
Hours differences become an integration issue
Working hours have emerged as a second fault line. ETU WA secretary Adam Woodage said Alcoa's shift and day workers have a 36-hour working week, compared with 42 hours for shift workers at Worsley. South32's day workers complete 40 hours across four 10-hour days. Woodage argued that those differences would come under greater scrutiny as the companies move towards combining their aluminium operations. He said employees wanted an agreement that recognised their skills, contributions and role in the business.
The hours comparison matters because the transaction would bring Worsley into a larger Alcoa portfolio that already includes Western Australian operations. Alcoa expects approximately USD 900 million in net present value from operational synergies, including improved integration between Worsley and its existing Western Australian operations. If comparable roles carry different working-time arrangements, the integration process will have to address how those terms are reconciled, not just how assets are combined.
The acquisition backdrop
Alcoa's proposed acquisition of South32's aluminium assets has an implied enterprise value of up to USD 5.6 billion. Announced in July 2026, it covers South32's 86 per cent interest in Worsley Alumina, full ownership of the Hillside Aluminium smelter in South Africa, a 33 per cent interest in Brazil's Mineração Rio do Norte bauxite mine, a 36 per cent interest in the Brazil Alumina refinery and a 40 per cent interest in the Brazil Aluminium smelter.
The consideration is structured as USD 3.1 billion in cash, approximately USD 1 billion in newly issued Alcoa shares, around USD 750 million in net debt and lease liabilities assumed by Alcoa, and up to USD 750 million in contingent cash payments linked to agreed alumina and aluminium price targets through 2030. Alcoa will also assume rehabilitation provisions estimated at about USD 1.2 billion, which are separate from the implied enterprise value. South32 intends to distribute about half of the Alcoa shares it receives, worth around USD 500 million at the time of announcement, to eligible shareholders through a fully franked special dividend after completion.
The transaction excludes Mozal Aluminium in Mozambique, which remains under South32 ownership and on care and maintenance. Completion is targeted for 29 June 2027, subject to regulatory and other closing conditions. South32 shareholders approved the transaction on 15 October 2026. Those approvals reduce one layer of uncertainty, but they do not settle the employment terms that would apply at Worsley after closing.
Why Worsley matters
Worsley's strategic weight explains why the dispute matters beyond the refinery gate. The facility has annual alumina production capacity of approximately 4.4 million tonnes. According to Wood Mackenzie, the acquisition would increase Alcoa's attributable bauxite production by 53.6 per cent to nearly 53 million tonnes annually and attributable alumina production by 51.6 per cent. The consultancy also estimates that Alcoa's aluminium smelting capacity would rise by around 26 per cent.
Once completed, the expanded portfolio is expected to produce approximately 14.8 million tonnes of alumina and 3.2 million tonnes of aluminium annually. Those figures make stable operations and experienced employees at Worsley an integration issue, not only a site-level bargaining issue. South32 said it was engaging constructively with employees and their representatives during enterprise agreement negotiations. It also said it had plans to maintain operations at Worsley during the industrial action and did not expect the stoppage to affect production.
What the dispute does and does not establish
The boundaries of the dispute are also clear. The unions have not called for higher bonus payments; they are seeking to preserve existing earnings through the enterprise agreement. South32 has not announced a change to its incentive policy; it says the policy will continue after completion. Alcoa has not yet completed the acquisition, and the transaction remains subject to closing conditions. South32 says it expects no production effect from the stoppage, while the industrial action is underway.
What happens next will depend on whether the enterprise agreement can convert the union's two concerns—short-term incentives and hours—into enforceable terms before ownership changes. A policy commitment from South32 may provide continuity after completion, but the union is seeking a binding agreement. If the gap remains, the Worsley dispute could become an early test of how Alcoa integrates acquired assets with different employment conditions.