However they were given a shock by a hard-working Scunthorpe side, that took a share of the spoils despite being on the back foot for long periods of the game.
This is the first League meeting between the two sides for 34 years and the highest level that Scunthorpe have played in for 43 years, and they certainly were not overawed by the occasion and the travelling Iron army celebrated at the end as though they had won a cup final.
There were early chances for both sides with Charlton's new skipper Andy Reid firing just over the bar and then seeing his free-kick deflected for a corner, while at the other end Charlton's new goalkeeper Nicky Weaver had to be alert to save from Jonathan Forte as United created the best chance of the opening period.
Charlton began to dominate the game and youngster Lloyd Sam wriggled through the visitors defence, but his weak shot was comfortably saved by Joe Murphy.
The Scunthorpe keeper also did well to deny Darren Ambrose, tipping over his fierce volley from Charlton's best chance of the goalless first-half.
Charlton had loud claims for a penalty when Marcus Bent appeared to be brought down by Iriekpen, but the home side took the lead after 62 minutes when Bent scored from close range for his 100th career goal, converting Sam's cross. The referee only gave the goal after consulting a linesman.
Forte thought he'd levelled moments later, only for a linesman to rule it out for offside.
United scored a shock equaliser on 69 minutes when Iriekpen - making his debut following a Bosman transfer from Swansea in the summer - rose unmarked above the Charlton defence to head home a Kevan Hurst corner.
It was Scunthorpe that finished the game better, although Charlton's Reid should have put the Addicks in front, only to screw his shot wide from close range.
But it was the home side that were hanging on at the end as the visitors twice put headers over the bar in a frantic finale.