From Sonic Retro
A technique originating in the Western Sonic canons, roboticization is the process of creating robots by transmuting living tissue into metal, producing Robians. It is distinct from the somewhat less invasive robotization, a method of simply imprisoning animals inside badniks seen in the early Sonic games.
Comics & TV
In the Sonic the Hedgehog cartoon, the roboticizer was originally created by Sir Charles "Uncle Chuck" Hedgehog with the intention of allowing the elderly to live longer. However, he was forced to abandon the project when test subjects began losing their free will. The machine was stolen and its purpose corrupted by Dr. Robotnik, then known as Julian, Minister of War for the Acorn Kingdom of Mobius. Robotnik considered the loss of free will to be a boon, and used the device to mount a coup of the Kingdom, transforming most of the population into his mechanical slaves. In a moment of irony, Sir Charles was roboticized by his own creation. According to the comic continuity, Sir Charles was also responsible for the roboticization of Sonic's father, Jules Hedgehog. Bunnie Rabbot was rescued from the roboticizer in the midst of the procedure, and is mechanical from the waist down.
According to the Sonic the Hedgehog TV series, although the roboticizer robs its victims of their free will, people who have been put through the process maintain their overall awareness of everything that is going on around them. They simply aren't in control of their actions. The "slave mind" effect can be fought, however. Sonic was able to help his Uncle Chuck regain his free will on multiple occasions, most notably through the use of emotion; Sonic finally managed to use his Uncle's emotional attachments and loyalties against his programming. However, if a subject is still roboticized, he or she can be plugged into a device that renders them subservient even after they have regained their free will.
The De-Roboticizer is a device that reverses the effects of Roboticization. It would effectively render the Roboticizer useless. Unfortunately, the device suffers major drawbacks. In the comic canon, the De-Roboticizer models built on Mobius are unrefined, and also potentially lethal. In the cartoon, the device's effects are only temporary, though they do allow the user to retain their free will.
By far, the worst De-Roboticizer is found in Sonic Underground. It is designed to scam money out of fearful aristocrats. The device supposedly restores people to normal, and claims to immunize them against Roboticization. Sadly, the device is a fraud, and Robotnik even made it into a Roboticizer to use on the Royal Hedgehogs as a trap. However, just as Sonia the Hedgehog was about to be roboticized, the inventor grew a conscience and pushed her out of the way, in the process getting himself roboticized.
Although the games mostly restricted themselves to the functionally similar but theoretically distinct robotization, flesh-to-metal transmutation is indicated to be a technique within Robotnik's arsenal during Sonic Chronicles: The Dark Brotherhood. Tails mentions the term in Mystic Ruins (Chapter 3), after defeating a squad of "Robodillos". The conversation is:
After defeating a second squad of mechanical armadillos, Tails salvages a box from the robot leader's head, which he says "must be what turned the animals into robots". Said box is presumably a portable roboticizer.