Ramaphosa had vowed to reform the companies as part of efforts to tackle state corruption, which he admitted blossomed under the nine-year rule of his predecessor Jacob Zuma.
Public Enterprises Minister Pravin Gordhan announced Phakamani Hadeb had been appointed permanent head of Eskom, the state-owned power monopoly on the verge of bankrupcy.
He also confirmed Popo Molefe as chairman of the Transnet transport company, while announcing further board changes at Transnet, arms manufacturer Denel and the SA Express airline.
"A number of the state owned enterprises are experiencing financial, operational and governance challenges. This has negative spillover implications for the economy," Gordhan said.
"The poor performance of these companies was a result of deep and widespread corruption and maladministration."
Gordhan criticised "stealing" by the management of SA Express, which on Thursday was grounded by the South African Civil Aviation Authority due to safety concerns.
Mismanagement allegations at the state owned companies have been linked to the wealthy Gupta business family, who are accused of receiving favourable government deals during Zuma's presidency.
Zuma was forced to resign as president in February as criticism grew from within the ruling ANC party over corruption allegations against him.
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