Iron Horse Roofing, Inc.- MadCow Roofing, Inc.

What is Galvalume?

The Benefits of Aluminum and Zinc

The composition of the Galvalume sheet alloy coating is typically 55% aluminum, 1.6% silicon and the balance zinc, nominal percentages by weight. The coating is applied to a substrate of steel bt apatented, hot-dip process developed by the Bethlehem reserach engineers. The result is a highly corrosion-resistant sheet steel that delivers the optimum combination of features of aluminum and zinc: the barrier protection and log-term durability of aluminum and the sacrificial or galvanic protection of sheared edges that characteristic of zinc.

Excellent Long-Term Durability

Galvalume sheet has been subjected to long-term testing for resistance to atmospheric corrosion. Test specimens of Galvalume sheet and competitive products are exposed at sites in four different environments: severe marine, marine, industrial and rural. After more than 23 years of exposure, Galvalume sheet continues to demonstrate an optimum combination of durability, edge protection and resistance to crevice corrosion. Typical durability for Galvalume sheet is two to four times that of galvanized G90 Sheet.

The accompanying photographs show atmospheric corrosion test specimens of G90 galvanized, Galvalume and aluminum-coated, type 2 steel that have been exposed to moderate marine and rural environments for 23 years.

Cut Edge Performance

Galvalume sheet provides superior cut edge performance compared to G90 galvanized sheet. This is mainly because the 55% Al-Zn coating remains on the steel sheet providing sacrificial protection for a much longer time period (2 to 4 times) than the pure zinc coating. This level of performance is particularly important in applications where sheared edges will be exposed or where localized damage to the coating may occur during fabrication or service.

Good Resistance to Crevice Corrosion

Galvalume sheet also demonstrates that it is more resistant thatn aluminum-coated, type 2 sheet to crevice corrosion in chloride-containing atmospheres.