The story
It was incorporated in 1965 as a Public Sector Undertaking. It is the first public sector enterprise in India which started producing aluminium in 1974. Till 2001, BALCO was a public sector enterprise owned 100% by Government of India. In 2001, Government of India divested 51% equity and management control in favour of Sterlite Industries India Limited.
There's a little history behind the privatisation of the company that was not doing so well being a public sector company. There were groups formed among people or rather BALCO employees namely supporters of privatisation and the ones who opposed it. Rallies and processions were carried out in the evenings to oppose the privatisation and those who supported it were left in minority. Eventually, things happened as they were planned and the company was listed under Sterlite. There were allegation of scam involved in disinvestment of BALCO.
From Wikipedia’s article on Bharat Aluminium Company, shared under CC BY-SA 4.0.5