Optimus Prime, and Ratchet go on a mission to check for a live Energon signal. When they arrive, it turns out to be a ship from the War on Cybertron, it is a crashed Autobot ship. Inside were many Mech carcasses that were rusty and covered in infected Energon.

Ratchet signaled not to touch the body. Because there is a possibility that the virus is still active. But the ship swayed which made Optimus fall and his face was hit by the infected Energon.

They are forced to return to base, and when they arrive. You see Optimus lying on the Medbay, his face looks.. rusty?

He lay weakly on the Medbay muttering Optimus Prime: "Hmm.."