The Australian Workers Union says its first wage negotiations in 20 years at Rio Tinto's Bell Bay Aluminium will give workers a greater say in working conditions.
The union's Tasmanian secretary, Ian Wakefield, said it was unlikely workers would push for wage parity with the mainland given the smelter's tough trading conditions.
Rio agreed to bargain collectively after Fair Work Australia found most workers wanted the union involved.
Bell Bay was Rio's first smelter to go non-union in 1994 and the company has negotiated directly with workers since.
``It means for the first time in 20 years workers will be able to have input in to the bargaining,'' Mr Wakefield said.
The new bargaining process to cover 350 workers will start in the next few weeks.
Rio claimed it was always prepared to negotiate with the union if it could prove the Bell Bay workforce wanted to collectively bargain.
``The AWU was not prepared to provide us with information to validate its claim to have majority support,'' a Rio spokeswoman said.
The union made an application to Fair Work Australia, which was satisfied a majority of employees wanted to bargain for a collective agreement.
``It is disappointing that the union decided to take this course of action when they could have provided this information to us directly,'' the spokeswoman said.
But Mr Wakefield said the union had given an undertaking to workers that the ballot would be confidential and going through the industrial umpire was the best method.
Last year the smelter reviewed its viability after tough competition from Asia, low steel prices and a high Australian dollar threatened profitability.
A cheap electricity deal struck with Hydro Tasmania was key in keeping the smelter open.
Mr Wakefield said the workers understood the tough environment better than anyone.