Bare Galvalume (pg. 3)

Important Considerations:

FASTENER AND FLASHING MATERIALS SELECTION

Fastener and flashing materials should be selected to provide the same long-term durability exhibited by Galvalume Sheet.

Based on accelerated corrosion tests and field inspection results, the following fastener materials have been found to exhibit the compatibility and long-term corrosion resistance necessary for use with Galvalume sheet:

• 300-series stainless steel
• Nylon
• Aluminum
• 400-series stainless steel, preferably with a zinc-plating or dichromate treatment to forestall cosmetic rust appearance
• Zinc/aluminum alloy coatings, although corrosion product appearance may not be suitable for all highly visible applications
• Steel, heavily coated with zinc (2 mils) and a dichromate treatment

The best fastener recommendations are available from your supplier or fastener manufacturer. (for additional information, refer to Bethlehem Technical Bulletin TB-207A, "Fastener Selection Guidelines for Use with Galvalume Sheet.")

Flashing materials compatible with Galvalume sheet steel include prepainted galvanized sheet steel, plastics, aluminum and Galvalume sheet itself, either painted or unpainted. Bare galvanized sheet steel is also compatible, but a heavier coating weight than that of conventional G90, such as G185 or heavier, is needed in order to approach the durability of Galvalume sheet steel. (Refer to Bethlehem Technical Bulletin TB-204B.)

COMPATIBILITY OF MATERIALS; WHAT TO AVOID

Galvalume sheet steel should not be used with lead, copper, graphite/amorphous carbon, green or wet lumber or treated wood. Cooper and copper-containing brasses, lead (for flashing or as contaminants in other materials) and graphite (from pencils used to mark components) should not be used in any construction where Galvalume or aluminum-coated sheet is specified. Even run-off from copper flashing onto Galvalume sheet should be avoided, as corrosion can be greatly accelerated. (Refer to Bethlehem Technical Bulletin TB-204B, "Compatibility of Materials Used in Metal Building Construction.")

HANDLING

To preserve the surface appearance of Galvalume sheet, only clean, dry gloves should be used during handling. Care should also be exercised to prevent the sheets from sliding over rough surfaces or each other.

STORAGE PRECAUTIONS

Galvalume sheet steel, like galvanized or aluminum-coated sheet steels, is subject to wet-storage staining. However, tests indicate that Galvalume sheet is more resistant to storage staining than galvanized sheet. Galvalume sheet turns gray to black if moisture is trapped between coil laps, cut-length sheets or roll-formed parts during shipping and storage. In its early stages, it appears as a white stain, similar to the stain that forms on galvanized sheet.

Bethlehem treats Galvalume sheet at the mill with a thin film of an inhibitive chromate-containing coating as a first defense against storage staining. The coils are also packaged in a dry area using a water-resistant paper. And the method of shipment (rail, truck or water) is also considered.

However, it should be noted that the protection afforded by these methods is only temporary. Shippers, fabricators, erectors and users of the material must also take precautions to keep it dry. (For additional information, refer to Bethlehem Technical Bulletin TB-206, "preventing Wet Storage Staining of Galvalume Sheet.")

FIELD PAINTING GALVALUME SHEET

Galvalume sheet can be successfully field painted by following established procedures and using readily available paints. The surface to be painted must be clean and dry and free of debris. Grease and oil may be removed with a mild detergent. Careful selection of the paint system is necessary to insure its compatibility with the metal and to promote adhesion. (Refer to Bethlehem Technical Bulletin TB-200A, "Field Painting of Galvalume Sheet" for more complete information.)

ANIMAL CONFINEMENT STRUCTURES

Bare Galvalume and prepainted Galvalume sheet are not recommended for use in pig and cattle confinement buildings. These structures are subject to extremely corrosive environments due to the presence of animal wastes and their decomposition by-products. Many coated sheet materials exhibit higher than normal rates of corrosion in these applications, even when good insulation and ventilation practices are observed. Galvalume sheet remains an excellent choice for other non-confinement agricultural applications. (Refer to Bethlehem Technical Bulletin TB-208, "Performance of Galvalume Sheet in Animal Confinement Applications" for more information.)