Do electronic corrosion prevention systems for cars really work, or
are they gimmicks that are relying on pseudo-science to sell?

The theory is valid but practice is impractical. It can work for
totally immersed objects but in which case sacrificial corrosion
blocks are more effective. On rig legs, the current flow between the
steelwork and the blocks (often zinc) can be many amps!

The problem with cars is that there is no way to complete the circuit
to all potentially (urg) affected parts. That?s why galvanising is so
effective because there is always intimate contact.

So though not pseudo-science, it is inappropriate science. Unless
someone knows better....

Best

The devices are totally bogus.  The Canadian government has gone after
the promoters.  The devives are said to work by impressed current
cathodic protection, but the car would have to be underwater for this
to be effective.
The galvanized sheet used in the cars produced today in the US has
just about solved all corrosion problems with body panels, see
http://www.a-sp.org/database/custom/cprotection/CorrosionProtection.pdf.

The devices are totally bogus.  The Canadian government has gone after
the promoters.  The devices are said to work by impressed current
cathodic protection, but the car would have to be underwater for this
to be effective.
The galvanized sheet used in the cars produced today in the US has
just about solved all corrosion problems with body panels, see
http://www.a-sp.org/database/custom/cprotection/CorrosionProtection.pdf.