First, lead will not show up as an identifiable object like clothing will however it will show up on the x-ray as an identifiable dark mass. This would immediately alert the staff and the bag would be pulled and possibly detonated, at a safe distance, by the bomb squad. They would assume that the lead was there to hide something sinister. Of course by this time you would be sitting in security trying to explain why you had lead in your luggage (and they do not have a sense of humour).
So yes, lead would show up on the screen
"hellmax" indicates that it is useful for hiding objects but the fact it is there would be obvious to the people viewing the x-ray and, in fact, highlight that there is something to be hidden. So it would, in fact, have the opposite effect.