Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Paint keeps oxygen and water from coming into direct contact with the metal, which prevents corrosion. Paint is more necessary because salt is an electrolyte that increases the conductivity of water and facilitates the flow of electric current between anodic and cathodic sites. Answer: corrosion
Output:
Paint keeps oxygen and water from coming into direct contact with the metal, which prevents what?