What material are water closet bolts often made out of due to corrosion resistance?

Water closet bolts are commonly made from brass because of its excellent corrosion resistance properties. Brass is an alloy primarily composed of copper and zinc, which provides strength and durability while resisting rust and corrosion that often occur in moist environments, such as those typically found in bathrooms. The corrosion resistance of brass helps prolong the lifespan of the bolts, ensuring that they maintain their integrity and functionality over time, especially when exposed to water, humidity, and various cleaning agents typically used in restroom cleaning.

Other materials listed, such as steel, are more susceptible to rust when exposed to moisture unless they are specially treated or coated, which might not always be sufficient in a bathroom environment. Iron is also prone to rust and corrosion and would not be suitable for applications where water exposure is frequent. While plastic can be corrosion-resistant, it may not offer the necessary strength and structural integrity needed for the secure attachment of a water closet. Thus, brass emerges as the ideal choice for water closet bolts in terms of durability and resistance to the elements typically found in their application.