Prepainted building panels have been successfully used for many years. Properly installed building panels under normal service conditions have excellent corrosion resistance and extremely long life expectancy. However, prepainted building panels may be subject to premature corrosion failures prior to installation if they are not handled and stored properly on the job site. Excessive storage periods or poor storage conditions can result in water intrusion into panel bundles. Prolonged exposure of bundled panels to wet conditions can cause paint blistering and substrate corrosion.
Environmental and Service Conditions
Water is a necessary prerequisite for corrosion of stored prepainted panels. When water or water vapor is available along the sides of a panel bundle, it may penetrate between the panels by capillary action. If proper precautions are not taken during transport, water may be present between the panels upon delivery at the job site.
Besides water, two other important factors that contribute to the corrosion of stored pre-painted panels are temperature and exposure time. Corrosion will accelerate with increased temperature. Given enough time, panel bundles will eventually become wet and storage corrosion may occur . Customer satisfaction can be increased, and storage corrosion can be prevented by:
- Reducing site storage time.
- Decreasing water contact.
- Moderating temperature extremes.
Pre-painted Panel Properties
Both environmental conditions and the pre-painted material itself influence storage corrosion. Specifically, the metal substrate, pretreatment, paint system and panel geometry can all contribute to the durability of the pre-painted panel in both the storage and service environments.
To minimize job site storage corrosion, panel bundles must be paper wrapped and possibly have cover (waster) sheets and end caps. Proper paper wrapping requires that the top sheet lap over the bottom sheet to shed water. The paper wrapping should have no folds or laps that could collect and hold water in or on the panel bundle.
The contents of each bundle must be described in an external packing slip to minimize damage to paper packaging required for receipt inspection. Generic labels may also be affixed to panel bundles describing proper handling and storage practices.
Panel bundles must always be carefully inspected when received at the job site. The bundles must be received paper wrapped as described above. The bundles must be examined for mechanical damage, rips and tears in the packaging and the presence of water. Rips and tears in the paper wrapping have to be repaired using water-resistant tape.
Proper handling of the individual panels and panel bundles is important for avoiding product damage and maintaining worker safety. Handling of panels and bundles is thoroughly addressed in the Metal Construction Association, “Guide to Metal Panel Shipping and Job Site Handling and Storage.”
Job Site Storage
Prolonged storage will always increase the likelihood of storage corrosion; therefore, the best prevention is to minimize the storage time. Proper storage limits the collection of water from rain, snow and condensation on the panel surfaces. Under roof storage is always preferred.
For more information on preventing corrosion, visit our Tool Kit.
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