Trade union Solidarity says its members at the petrochemicals firm Sasol will embark on a three-week strike starting on Thursday.
This after they went on a go-slow protest on Monday over a share scheme that the firm has exclusively offered to black staff.
South African companies are required to meet quotas on black ownership, employment and procurement as part of a drive to reverse decades of exclusion under apartheid.
Meeting the rules makes a company more likely to qualify for government tenders.
Solidarity has been waging a challenge against racial quotas in the workplace.
It lodged a complaint against the policy with the UN Human Rights Commission in 2016.
Economist Yashodan Naidoo says Solidarity is being unreasonable.
Naidoo says Solidarity is a union which has shown its colours many times regarding which side of the fence it sits on, so it’s no surprise that they would go on strike.
