Anti-rust protection at the Yaris

Halllo Yaris owner I bought a Yaris for my daughter, during the preliminary inspection I stated that the rust prevention is not exactly good, in some cases only sporadically applied underbody protection otherwise only the bare sheet metal. Had then agreed with the dealer a later wax treatment. Now my question to the owners of older Yaris vehicles, is rust a topic, or is the protection attached ex factory sufficient? Greeting Aljubo