Richard Brodie scored the only goal of the game with a late effort from a free-kick, it followed a period of pressure from the home side who deserved the win.
United played a reserve team, and the first-half saw few chances. The best opportunity saw Jonathan Forte's short turned away by Michael Ingham.
Bobby Grant forced a save out of Ingham with a curling shot from outside the area just before the break, but it was a routine save.
The best chances of the second-half for the Iron were tame efforts from Martyn Woolford and and Matthew Gooden that were hit straight at the home keeper.
The biggest concern was an injury to Eddie Nolan, who had to be replaced by Rory Coleman early in the second-half after a heavy tackle while offering support to Woolford on the left wing.