The Addicks have offered a contract to Hayes, 27, and expect him to sign when he returns from a family holiday.
A club statement said: "The club is confident it will beat off interest from two other clubs who competed in last season's Championship so Hayes will be present when pre-season training begins at Sparrows Lane at the end of the month."
The comment from Charlton raises the possibility that Hayes was a target for the Iron, for whom he has already had two successful spells.
A third spell in North Lincolnshire was in the offing last season, but a proposed loan move was never finalised.
He has twice left Glanford Park on Bosman transfers, but his move to Preston North End last summer did not work out and he quickly fell away from the first-team picture at Deepdale.
Should he sign for Chris Powell's side, he could face Scunthorpe as an Addicks player in a League One game at The Valley on Saturday August 20.
Charlton have so far signed Danny Hollands, John Sullivan and Bradley Pritchard, and have agreed a deal for rookie goalkeeper Nick Pope.