Sacrificial Electrodes on a Car?

Question

I know that sacrificial electrodes are used on outboard motors and in other marine applications to reduce or eliminate corrosion from salt water, etc. Could pieces of zinc be attached to an automobile frame to prevent rusting of the steel frame?

Answer 1

Putting zinc in one spot will not protect another place that is not part of a complete circuit (i.e., immersed in electrolyte). A boat in water is immersed in that electrolyte.

However: the whole part is protected if covered with the sacrificial metal.

For example, automobile exhaust mufflers at one time were commonly aluminized... which worked well on the aluminized exterior, until it wore through from abrasion or attack from moisture and road salts. The exhaust system often rusted from inside, though, which was not aluminized -- had the water condensed from the exhaust, inside the muffler, been contiguous with the aluminized exterior, there might have been less rust inside. Now, exhaust systems must meet governmental regulations to last a certain time and/or distance, and are often made from stainless steels.

Galvanized (sacrificial zinc-coated) steel is also widely used in automotive applications. Dipping in molten zinc leaves pretty spangles, which do not make for a smooth body finish, so electroplating is used, instead. If you think about it, we use electricity to deposit the zinc, then use electricity generated by oxidation of the zinc to protect the substrate.