About 75% of the North American coil coating industry is dedicated to building products. Since the lifetime of these products is measured in decades, as opposed to merely years, the weathering performance of the coatings used for this market is critical. Understanding how coatings perform, therefore, is essential. There are many approaches to studying weathering performance, and one of the more interesting techniques to accelerate the weathering process involves the devices described in these two ASTM standards:
It goes by many names: prepainted metal, coil coated metal, prefinished metal. Each of these descriptions refers to the product of a coil coating line, sometimes called a continuous coil line (CCL). Prepainted metal is commonly used as a coated product in construction applications (metal walls and roofs are two examples), as well as appliances, HVAC units (air conditioners, furnaces, etc.), rainware products (gutters, downspouts, flashing, etc.), and many others. Prepainted metal is the product; a CCL is the application process used to produce prepainted metal.
Part One (of Three)
When you look at a piece of prepainted metal, what do you see? Certainly a colorful article that may or may not have some shape to it. Often the metal is fabricated with “ribs” to add structural strength to the panel, or it may be flat, as is the case with a metal composite material (MCM) panel. The surface of the prepainted article might be a smooth, homogeneous surface, or it may have a wood-grained pattern, or it might have a subtle pebbly texture. The color of prepainted metal ranges from whites, grays, and blacks to neutral earth tones to saturated, brilliant colors. Some of the colors have metallic or color-shifting effects. But this layer of color is only what you actually see. What you don’t see is all that is under the surface. Continue reading
By Kelvin Russell, Precoat Metals
Chances are, if you’re reading this blog regularly, you already know that prepainted metal is the substrate of choice for metal buildings, HVAC products, appliance products, and more. The list of applications for prepainted metal is endless, as are the reasons why prepainted metal is the substrate of choice for so many products. To be honest, this long list of reasons is not the subject of today’s post, save one: aesthetics. So many beautiful colors! Color and texture can make blockbusters out of the ordinary products we take for granted. In addition to the performance benefits of prepainted metal, its almost limitless beauty is quickly rising to the top of the list of reasons why consumers choose it for any number of applications. But then tradition steps in and says, “You can’t use metal here, it has to be wood!” Well, phooey. Now what? Continue reading
Parts One and Two of this series of posts on NCCA’s “The Color Project” discussed why we needed to run a visual assessment experiment and how we structured the study. You may recall that we created 54 panel pairs, and within this set there were 15 repeats (i.e., pairs that were shown to the observers—unbeknownst to them—a second time to see how closely they would rate the pairs), as well as 8 pairs of identical panels (i.e., take a panel, cut it in half, tape the halves together, and call it a color difference pair). I also mentioned the tedium of collecting data for 13 solid hours. And lastly, I teased you with promise of revealing data here in Part Three. So, without further ado, let’s dive in. But first, let’s discuss the visual observations. We’ll talk color data later. Continue reading
In the last post, Part One, we left off with two facts: We depend on a numerical description of color and color difference rather than judging a sample vs. a standard visually; and NCCA began to investigate ΔE2000 to determine how well it might work in the coil industry.
Let’s start Part Two with a short discussion on ΔE2000. It is way more than the usual ΔE with a little “2000” as a subscript. (If only it were that easy.) Our current ΔE is a straightforward root-mean-squared calculation, as shown here:
ΔEHunter = [(L2-L1)2 + (a2-a1)2 + (b2-b1)2]1/2
The National Coil Coating Association Technology Committee has been investigating color measurement, color difference, and how best to establish meaningful color tolerances. “Color” is a small word, but one with lots of tentacles. You see a blue car, you call it a blue car. The person you’re walking down the street with also describes this same car as blue. So you both call it “blue.” What’s the big deal? Seeing a “blue” car as it travels down the street is one thing. Putting two metal panels next to each other and comparing their colors closely and carefully is quite another thing. It’s all a matter of perspective. Continue reading