The Industrial Union on Friday issued a new strike warning to the employers' groups Technology Industries of Finland and Chemical Industry Federation of Finland.
Additionally, Trade Union Pro, one of the country's largest trade unions, issued a strike warning to Technology Industries of Finland, which would affect operations at 21 companies if it is carried out.
Union members staged a series of other strikes towards the end of last year.
According to the Industrial Union, the planned six-day series of strikes would start on 27 January and end in early February.
The 50 companies that would be affected include Metso, Wärtsilä and Valmet. The union has posted a full list of the affected companies on its website.
If the strikes go ahead, they will affect around 13,000 employees.
According to the employers' group CEO, Jarkko Ruohoniemi, the strike warning was not a surprise. He said the negotiation situation had not changed since the beginning of December.
"The parties have not reached a common view on realistic wage adjustments in coming years. We've offered [wage] levels that would significantly improve [workers'] purchasing power, but this does not seem to be sufficient for the trade unions," Ruohoniemi said.
Users with an Yle ID can leave comments on our news stories. You can create your Yle ID via this link. Our guidelines on commenting and moderation are explained here.