Is stealing iron from a company that has departed unlawful (haram) or lawful (halal), and how can one atone for this sin?

If the iron was taken after the company had left and abandoned it, then it is permissible to own and sell it, based on the opinion of Ibn Uthaymeen in "Al-Sharh Al-Mumti'" that whatever its owner abandons out of disinterest, it is permissible to take, such as the burnt frame of a car. However, if it was taken before the company left and without its permission, then one must repent and return the value of the sold iron to the company, without needing to inform them of what happened.