What is electrolytic protection?
I understand why a HS text might call it "electrolytic" , but in the real world it is called "cathodic protection" or CP. That is what to look for on the net. It is a multibillion dollar industry. Essentially all pipelines ( oil, gas, products, water , etc.) use it . A large majority off offshore steel structures ( oil  platforms, ships, etc) use it. And many steel products are galvanized . There are two basic types ; sacrificial coatings and impressed current. Sacrificial coatings are represented by galvanized steel , also aluminum and cadmium coatings. Impressed current, CP is also  two categories : Sacrificial anodes , usually aluminum ( which do not use rectifiers) , and inert anodes , usually titanium or graphite. These are buried in soils made more conductive with graphite powder (typically) and electrically connected to rectifiers  which are then connected to the steel to be protected . The voltage is adjusted and monitored along the protected steel , eg. pipeline. Pipelines are coated with an electrically insulating coating to reduce the amount of current required to maintain a protective voltage , normally lower than - 0.65 V ( Cu - Cu SO4 half cell) Too low a voltage can cause hydrogen gas bubbles under the coating and hydrogen embrittlement of certain steels.There is also anodic protection but it has very specific limited applications. So, there is such a thing as "electrolytic" protection.