Which metal is NOT listed as a corrosion-resistant material for roof valley linings?

• A. Aluminum
• B. Galvanized steel
• C. Stainless steel
• D. Cold-rolled copper

Answer: (C)

In roof valley lining, the metal chosen must stand up to constant moisture and outdoor weather while being easy to form and install. Aluminum is favored because it resists atmospheric corrosion, is lightweight, and easy to work into valley shapes. Galvanized steel offers durable protection through its zinc coating, giving sacrificial corrosion resistance that holds up well in exposed roof areas. Cold-rolled copper is highly durable and develops a protective patina over time, providing long-lasting performance in contact with roofing materials. Stainless steel, while very corrosion-resistant, is not typically listed for valley linings due to higher cost and practical considerations—other common metals already meet the needed resistance and provide sufficient compatibility with standard roofing assemblies.