Regenerative Bio-steel is a material developed by Egon Stetmann after researching the cellular structure of zerg organisms. It uses regenerative nanobots to slowly repair the hull of whatever vehicle it is made from. While the process is slower then that of an SCV repair, it can serve to aid frontline vehicles when the need is dire.
In-game, the rates of healing vary wildly, from approximately 0.6/s in Wings of Liberty, to 10 in Nova Covert Ops, and 2/s in Co-op Missions. In the two campaigns it is typically passive and requires reaching some zerg objective.
Damaged mechanical units recover hit points when out of combat, at a rate of 0.6015 each second.
Our ship and vehicle hulls are now made from a material called Regenerative Bio-Steel. This material uses internal nanobots to slowly repair any damage the hull sustains. While this regeneration process is much slower than conventional SCV repairs, it can be the difference between life and death if no SCVs are available.