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Accelerated Weathering: Part Two

Part One of this blog described some of the difficulties associated with accelerated corrosion testing. The chemistry is complex. There are many microclimates to consider. And the list goes on. There is good news, however. We are not alone. Extensive amounts of research across all coatings areas is done and reported routinely.

french-corrosion-instituteAs a Part Two blog on accelerated corrosion testing, here is a sampling of work done by the French Corrosion Institute, an organization that has done a great deal of work in the past with the European Coil Coating Association. The bullet points following the titles and attributions are my own comments from reading the documents: Continue reading


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Accelerated Weathering: Part One

“Not this topic again,” you might say. By “this,” you probably inferred that you are about to read a few hundred words describing the difficulties of meaningfully correlating accelerated weathering to real-time performance. Rest easy; that old topic is kids’ stuff compared to understanding the meaningfulness of corrosion testing.

The performance of coil coatings over the lifetime of a product is of paramount importance. Of the markets served by prepainted metal, the building products market poses the greatest challenges. During a recent NCCA meeting, there were plenty of conversations about accelerated corrosion testing, and this got me thinking about the similarities—and distinct differences—when comparing accelerated corrosion testing and accelerated weathering. Of course, corrosion is a form of weathering, but the term “weathering” commonly refers to what happens to a product’s appearance properties (chalk, fade, gloss retention) when exposed to sunlight, heat and moisture.  On the other hand, corrosion refers to the degradation of the metal substrate.

Great progress has been made over the last 20 years to understand how to model an accelerated weathering test to better simulate the environment in which a product will be placed. We now have a better understanding of the need to duplicate the solar power distribution, the unrealistic effects of <295 nm UV wavelengths, and, most recently, the importance and necessity of coating moisture imbibition in the physio-chemical degradation of coatings. This level of understanding is mostly absent when it comes to accelerated corrosion testing.

What makes corrosion testing so difficult? Let’s start with the chemistry of corrosion versus accelerated weathering. Don’t worry; I do not intend to get into the chemistry and physics. We’ll leave that to the researchers, but it is important to know that these researchers are always striving to duplicate in an accelerated test cabinet the same chemistry that is taking place in the real world. When done effectively, new products can be introduced with an assurance that they will perform suitably in the field.

As demanding as it is to understand the degradation reactions of an organic coating during typical weathering, understanding corrosion reactions is way more convoluted! Continue reading


Preventing Job Site Storage Corrosion of Pre-painted Building Panels

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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: Continue reading


Five Benefits of Using Coil Coated Metal

Since the 1930s, pre-painted metals have become the superior choice in coating options in a variety of different ways. From going green to saving green, here are just a handful of the reasons why coil coating is becoming the future of the coating industry.

Beauty:

Architects, manufacturers and consumers appreciate the beauty  and benefits of coil-coated metal, including consistent quality, low cost, design flexibility and green properties. Many savvy manufacturers now know that pre-painted metal can be easily fabricated and joined.coil-coating-process-prepainted-metal-header-image

Durability: Continue reading