Which fastener material should not be used to fasten tiles?

Electro-galvanized fasteners, while often used in various construction applications due to their affordability and corrosion resistance, are not recommended for fastening tiles. This is primarily because electro-galvanizing provides only a thin zinc coating that can wear off over time, especially in moist environments where tiles are typically installed, such as bathrooms or kitchens. Once the zinc layer wears away, the underlying steel is susceptible to corrosion, which can lead to rust stains that damage the tile and the underlying structure.

In contrast, materials like stainless steel, which have a much higher resistance to corrosion due to their alloy composition, are ideal for tile installation. Similarly, aluminum and galvanized steel offer better protection against rust in various environmental conditions, making them more appropriate choices compared to electro-galvanized fasteners.