The Trade Union Pro announced on Sunday that 14,000 of its members will begin a two-week strike at major export corporations on 27 January unless a new contract is agreed by then.
The Industrial Union has also announced a two-week strike for the same period, likewise covering about 14,000 workers. Meanwhile the Paper Workers' Union says 9,000 of its members will walk out on the same day, likely closing the nation's paper mills.
All three job actions are to run from midnight on 27 January until 9 February.
The companies affected by the Pro action include industrial giants such as ABB, Metso, Nokia, Outokumpu, Meyer Turku, Patria, Rautaruukki, Valmet and Wärtsilä.
On Friday, Pro imposed a ban on overtime and shift swaps in the sector.
It says the strike is needed since no agreement has been reached in collective agreement negotiations with the employers' umbrella group Technology Finland.
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Ghosts of 2016 competitiveness pact
The main sticking point is an extra unpaid 24 hours added to most salaried employees' annual workload back in 2016. That was part of the centre-right Juha Sipilä government's so-called competitiveness pact ('kiky'), aimed at boosting Finnish exports.
"Technology Finland's refusal to remove these 24 hours of free work from white-collar workers' contracts leaves us no other option than to announce a new work stoppage and the ban on overtime and shift swaps," Pro union chair Jorma Malinen said in a statement on Sunday.
The union says that the so-called 'kiky hours' – totalling about three working days annually – have been dropped for most other workers in the technology industries, but that employers want to keep forcing white-collar staff doing 'volunteer work'.
"Not workable or sensible"
"Managers and experts should work even if [other] employees are not there – not a workable or sensible solution. In addition, Technology Finland does not want to pay general wage increases to white-collar workers at all, but rather to be able to decide who get such raises and how much," Malinen asserted.
In early January, Technology Finland reached a contract deal with rank-and-file workers in the sector, represented by the Industrial Union.
Malinen said that Pro is ready to fast-track talks "if the employers' associations have a genuine desire to reach an agreement".
Pro represents 120,000 educated professionals, experts and managerial staff in sectors including heavy industry, finance, services, IT and communications. It is the biggest bloc within the Finnish Confederation of Professionals (STTK).
Malinen has led the union since 2015, when he took over from Antti Rinne, who had led the union since its inception in 2011. Rinne went on to lead the Social Democratic Party and become prime minister last summer, only to resign in early December.