Extensive testing confirms top quality
Research engineers at Bethlehem developed Galvalume sheet in the mid-1960s. Introduced commercially in 1972, it has enjoyed the fastest growth rate of any steel product on the world market.

The long-lasting resistance of bare Galvalume sheet steel to atmospheric corrosion is well established throughout the metal building industry. Results are conclusive: Bare Galvalume sheet is at least two to four times more resistant to atmospheric corrosion than G90 galvanized sheet - and at least comparable to aluminum-coated Type 2 sheet in durability - while providing superior galvanic protection and crevice corrosion resistance.

It is not surprising, then, that prepainted Galvalume sheet is also demonstrating excellent resistance to corrosion. In laboratory tests, as well as in controlled, real-life tests throughout the United States, prepainted Galvalume sheet outperforms prepainted galvanized G90 sheet.

Flexibility and paint adherence
The accompanying photographs below are 1.3 x magnification views of prepainted sheet deformed by an 80-inch-pound reverse impact. A tape-pull has been used to evaluate the paint adherence after deformation. Prepainted extra-smooth Galvalume sheet is on the left and prepainted minimized-spangle, extra-smooth galvanized sheet is on the right. Both substrates were painted with the same primer systems and topcoats. The Galvalume sheet was painted with a chromate pretreatment, while the galvanized sheet was painted with a complex oxide pretreatment.

Prepainted Galvalume sheet is seen to be less susceptible to micro-cracking and loss of paint adhesion during forming. This finding is consistent with laboratory forming evaluations which have demonstrated that the 55% aluminum-zinc coating can withstand higher strain levels before a crack penetrates to the base steel, compared to a 100% zinc coating. Thus, prepainted Galvalume sheet can more easily accommodate the strains encountered in typical roll forming operations used to manufacture metal panel components. Such paint formability benefits are important for protection against atmospheric corrosion.

Prepainted Galvalume Sheet	Prepainted galvanized G90 sheet

Eight-year atmospheric exposures
After eight years exposure at four different test sites, prepainted Galvalume sheet exhibits superior overall performance compared to prepainted galvanized G90 sheet. Each material was painted with Bethlehem-approved paint systems. The only difference in processing was the use of a chromate pretreatment for Galvalume sheet versus a complex oxide pretreatment for the galvanized sheet.

Galvalume sheet vs. galvanized sheet
At the relatively severe Kure Beach, NC exposure site, 250 meters from the surf of the Atlantic Ocean, prepainted Galvalume sheet, left, exhibits excellent corrosion protection along a scribe used to simulate panel damage. By contrast, the galvanized G90 sheet, right, exhibits light rust staining and the onset of paint creepback from the scribe. Also of concern, is the appearance of micro-blisters over the entire surface of the sheet. (Photographs below are at 4x magnification).

Prepainted Galvalume Sheet	Prepainted galvanized G90 sheet

Edge creep
Edge creep can be defined as paint undercutting along sheared edges on prepainted metal sheets. Bethlehem's prepainted Galvalume sheet exhibits consistently minimal edge creep which tends to taper off to less than a millimeter after eight years exposure at our most corrosive test site. (See following chart.) Adherence to Bethlehem's Process Specification is reflected in this excellent, long-term behavior.

By contrast, galvanized G90 sheet, prepainted with conventional paint systems, exhibits more variable edge creep performance. The overall range of edge creep corrosion has also begun to increase beyond 6 years exposure.

Bethlehem Technical Bulletins
As with all materials of construction, there are guidelines for obtaining optimum performance in the field. The Technical Bulletins listed below have been developed by Bethlehem engineers to provide guidelines for the proper application of prepainted Galvalume sheet components.

• Field Painting of Galvalume Sheet, TB-200A
• Guidelines for Welding Galvalume Sheet, TB-201
• Design, Construction and Maintenance Guidelines for Galvalume Sheet, TB-203
• Compatibility of Materials used in Metal Building Construction, TB-204A
• Coating Weight and Thickness Designations for Coated Sheet Steels, TB-205
• Preventing Wet Storage Staining of Galvalume Sheet, TB-206
• Fastener Selection Guidelines for Use with Galvalume Sheet, TB-207A
• Performance of Galvalume Sheet in Animal Confinement Applications, TB-208

Warranties
Warranties are available to cover base metal and paint systems. Bethlehem offers standard paint protection warranties of three years (white roofing applications) and five years (white and color siding applications) on its prepainted Galvalume sheet. Longer warranties are available from the paint supplier and coil coater.

In addition, subject to the terms of the warranty, the base metal of prepainted or unpainted Galvalume sheet roofing or siding is guaranteed by Bethlehem not to rupture, fail structurally, or perforate due to corrosion for a period of 20 years and 6 months. The warranty assumes that the material is used in accordance with the manufacturer's instructions. Contact Bethlehem for more details concerning the warranty available for prepainted Galvalume sheet.

Design resources
Helpful design resources are available on the use of metal architectural systems and components, a number of which are listed below. You are encouraged to consult these resources for additional technical information.

1. Architectural Design Guidelines
"Architectural Design and Planning Guidelines," Building Systems Institute, 1230 Keith Building, Cleveland, Ohio 44115.

Vonier, Thomas: "Beyond Shade and Shelter: Pre-engineered Metal Building Systems," Progressive Architecture, March 1982.

2. Structural Design and Wind Loading Specifications
"Specifications for the Design, Fabrication and Erection of Steel for Buildings," American Institute for Steel Construction.

"Specifications for the Design of Cold-Formed Steel Structural Members," American Iron and Steel Institute.

"1986 Low Rise Building Systems Manual," Metal Building Manufacturers Association, Cleveland, Ohio.

"Class 90 Rating for Wind Resistive Construction," Underwriters Laboratories.

3. Materials Specifications
Galvalume sheet is described in American Society for Testing and Materials (ASTM), Designation A792, and is usually ordered in one of two coating classes: AZ50 or AZ55.

Bare and prepainted Galvalume sheet steel have been incorporated with guide specifications for metal building systems and components by the U.S. Army Corps of Engineers. The applicable specifications are CEGS-07413, CEGS-07415, CEGS-07416 and CEGS-13120. Prepainted Galvalume sheet is also recognized in the Department of Navy guide specification NFGS-13121 and NFGS-07410.

4. Additional Contacts
A significant advantage to users of metal building systems and components is the availability of expert, experienced technical advice and consultation, usually when and where it is needed, and at no charge. Each of the organizations listed below offers design assistance and technical consultation. Each will also provide information on the availability of products that match specific project requirements.

• Metal Building Manufacturers Association, Cleveland, Ohio.
• Metal Construction Association, Washington, D.C.
• Building Systems Institute, Cleveland, Ohio.
• Systems Builders Association, Arlington, Texas.

Galvalume® is a registered trademark of BIEC International, Inc. or one of its licensed producers.