Alright, let's talk comic books. Remember when Tony Stark realized the weapons of his company were bombing innocent people and ironically one lands near him? Remember what he did? We all praised him for that. Wow, he stood against war, against genocide, war profiteering, all of it.

He took his money and did something good with it. He realizes he can't be the sleazy playboy billionaire and ride off the success of his parents arms company. He builds the first suit. He became Iron Man. He stood against the very evils his company was built on. Sometimes he fights alongside America's interests, other times he doesn't want to be their puppet and admits he fights for what HE KNOWS is right.

Therefore, in sort of a fictional way, he's incorruptible.

He makes mistakes sure, he battles his ego, but he learns from every experience and grows from it.