Australian minerals and metals giant BHP Billiton has appointed Kotak Mahindra Capital (KMCC) as its investment banker for the Nalco privatisation process, according to reports. Goldman Sachs has a 26 percent stake in KMCC, the investment banking arm of the Kotak Mahindra Group. KMCC officials declined to comment.BHP-Billiton is the third international metals major to appoint an investment banker in preparation for a possible bid for Nalco.