|Refinishing Metal Buildings|
Metal buildings are made from coil-coated stock. Large coils of metal, steel, galvanized steel, and aluminum are painted on a coil coating line. The coil is unrolled, cleaned, metal treatment is applied, a primer is applied and baked, a top coat is applied and baked, and the coil is rolled up at the end of the line. The coating process is very fast with line speeds of several hundred feet a minute. The coil is then shipped to a metal building manufacture who cuts the coil into pieces and forms the pieces to the desired shape.
The most common types of factory-applied coatings used on metal buildings are polyesters, silicone polyesters, organosols, plastisols, and fluorocarbons. All can be recoated.
Metal buildings are a good substrate to paint since they are dimensionally stable and don't crack like wood surfaces do. With care in surface preparation, selection of primer and topcoat, and good application, a repaint job's longevity can approach the life of the original baked on factory finish.
The surface must be clean. There are four things that usually must be eliminated before priming can occur: dirt, grease and grime, mildew, chalk and rust. Rust must be removed by brushing with a steel brush. A power wash will normally, but not always, remove dirt and chalk. Usually, plain water will do the job. If cleaners or bleach is used in the wash, the chemicals must be rinsed off before priming. After power washing, the surface should be rubbed with a black cloth. If there is evidence of chalk on the rag, the remaining chalk must be abraded off by scrubbing with a brush followed by a rinse. Paint will not stick to a chalky surface. A chlorine containing chemical such as household bleach will remove mildew. If bleach is used, it must be rinsed off before priming.
After the surface has been prepared, spot prime the rusted areas and any areas that shows bare metal with a good rust inhibitive primer such as 471-00 Aqua Borne Acrylic Primer/Basecoat. This primer may be applied by brush, roller or spray. Thin very sparingly with water if necessary. Use a .017 to .021 tip on an airless gun. Allow to dry 2 hours under normal conditions before recoating. Do not apply below 50°F.
After spot priming, apply a full coat of 471-00 Aqua Borne Acrylic Primer/Basecoat to the entire surface. Let dry for at least 2 hours under normal drying conditions. Do not apply below 50°F. One coat of primer will give adequate protection, but for optimum results, two coats is recommended. The minimum recommended system is: spot prime, prime the entire surface and one top coat. For maximum longevity approaching the life of the original factory baked on finish, the recommended system is: spot prime, two coats of primer followed by two coats of top coat.
If the surface has minor scratches that need to be disguised, 320-00 Aqua Borne Acrylic Blockout/Undercoat will provide the build needed to hide minor defects. 320-00 is a superb primer and undercoater that can be used in place of 471-00. However, 471-00 should be used to spot prime rusty areas since 320-00 has only minimal rust inhibitive properties.
After the primer is thoroughly dry, apply a coat of 152 Aqua Borne Ceramic™ Acrylic Soft Gloss House Paint if a semi-gloss finish is desired or 142 Aqua Borne Ceramic™ Lo-Sheen House & Trim Paint if an eggshell finish is desired. Apply by brush, roller or spray. Thin sparingly with water as needed. Do not apply under 50°F. Use a .017 to .021 tip for airless spray applications. Both finishes dry to a hard, impervious finish that resists dirt pickup and is non-chalking. One coat will give long lasting protection, but two coats is recommended for the utmost in durability. Allow the first coat to dry thoroughly before recoating. At least two hours under normal conditions is needed before recoating.