MSC corporate comms manager Paul Weigh said Onillon, who takes the new post of director of investor relations in June, would boost investor interest in the New York and Amsterdam stock exchange listed company among existing and potential shareholders.
'Interest from the investment community has massively increased,' said Weigh.
'We have a lot of new shareholders on board and we want to increase dialogue with the investment community,' he added.
Onillon will work alongside head of North American investor relations Tom McCue. Both report to MSC president and chief financial officer Aditya Mittal.
The move comes in the wake of MSC's formation last year, when Ispat International, 77 per cent owned by Indian tycoon Lakshmi Mittal's family, conducted a reverse takeover of its privately owned LNM Holdings through an issue of around £7.2bn in shares.
At the same time, MSC announced the acquisition of the International Steel Group for £2.4bn in a cash and shares deal completed last month that created the world's largest steel manufacturer. It now has a market capitalisation of around £11bn and production capacity of about 70 million tonnes a year.
Onillon arrives as the outlook for the world steel market becomes less certain.
'Lots of commentators have been talking about a slight slowdown in world steel prices,' said Weigh. 'In the first quarter, we said we expected prices to soften in the following quarter, but we are still experiencing good global demand.
'China has been a net importer and industry commentators have said that it could become a net exporter in the next couple of years.'