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Coatings Technology: Learning to Accommodate the Local Weather

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We’ll confine our discussion here to obvious weather differences, but we won’t get into how coil coatings formulators accommodate those differences. That’s a discussion for another day. Just know that steel and aluminum companies, pretreatment suppliers, and coatings chemists are working hard to formulate a coil coating system that provides the necessary performance for a particular region.

One size rarely fits all, and the same is true about coil coating technology. What makes sense in Europe may not make sense in the U.S. What performs well in the U.S. may perform poorly in Australia. Different environmental conditions demand different approaches to providing a coil coating system that can stand up to the demands of the local environment on the substrate, the pretreatment, and the coatings.

When you check the local weather forecast, you will always learn three things: the temperature, the amount of sunshine, and the outlook for precipitation. Sure, there’s pollen count, UV index, and other seasonal data, but we are mostly interested in average annual data to demonstrate differences around the globe. First let’s look at temperature.

In the map below you will find the annualized average temperature for all parts of the globe. The hottest areas are near the equator. No surprise, right? But there are indeed some surprises. Look at how hot Australia is, especially considering how far south it is. And notice how the continent of Europe is more or less consistent in temperature. Europe lies far more north than other population centers around the globe. The same temperature equivalency is not true in the United States. Florida is hot, and the South-Southeast regions, while not as hot on average as Florida, are certainly hotter than the Northeast-Midwest-Northwest regions. NOTE: The U.S. map is correct: Florida, on average, is hotter than Arizona.

How can this be, given how blazing hot places like Phoenix can get, and especially given the fact that it rarely hits 100 °F in Miami? It’s because the nighttime temperatures in, say, Phoenix, drop a lot at night, whereas the nighttime temperatures in southern Florida do not drop nearly as much. Desert vs. the Everglades; dry air vs. moist air—that explains everything. And it is how “average temperature” may sometimes mislead you. A cheap plastic object may become dramatically more degraded in Phoenix at 125 °F than it does in Miami at 90 °F, since more bad things happen to that plastic at the high temperatures occurring in Phoenix. We know the paint systems used today for coil coated building products can take the heat very well, certainly much better than a cheap plastic object. While heat is important—heat always accelerates degradation—water is necessary in addition to UV radiation to degrade high-performance coatings.

So now let’s see what precipitation looks like around the globe.


https://upload.wikimedia.org/wikipedia/commons/9/92/Annual_Average_Temperature_Map.png

Phoenix may be hot, but it sure is dry. The area east of the Mississippi River is quite similar to Europe for precipitation, as is the eastern region of Australia, which is where most of the people live on that continent. It’s hard to see on this map, but southern Florida (Miami, Homestead, Tampa) is dark green, meaning it has distinctly more rainfall than central Florida. And this is why nearly everyone interested in weathering chooses southern Florida to expose their panels: it’s hot and wet, and we haven’t even gotten to sunshine yet.


“Total Annual Rainfall,” by Joseph Casey.
https://www.climate-charts.com/World-Climate-Maps.html#rain

We all know about the effect that UV radiation has on our skin, and it’s really no different for organic coatings, the “skin” of a coil coating system. The greater the amount of UV, the more damaging the effect. Below is a global map showing solar energy levels, which tells you a lot about the more- and less-demanding areas around the world. Southern Europe (Madrid, Rome, Athens) is similar to much of the U.S. Much of northern Europe (London, Amsterdam, Stockholm) shows quite gentle amounts of UV, similar to Toronto and Vancouver. Surprisingly, everything south of the Tropic of Cancer, except for the western part of South America—gets a heavy dose of UV. Australia gets hit hard with UV, especially given that it lies south of the Tropic of Capricorn. Melbourne, Australia, for example, is about 40 degrees south latitude, which is similar in the Northern Hemisphere to Philadelphia, Columbus, Indianapolis, Denver, and Reno. Sadly, there is no simple rule regarding latitude when it comes to weathering.

Onward to corrosion. Here is map of chloride deposition throughout the world.


https://www.researchgate.net/figure/Distribution-of-atmospheric-corrosivity-on-the-global-map-final-results-of-GIS-analyst_fig5_233841501

Although it is apparent that coastal areas have high corrosivity, check out Europe. The entire continent is bathed in chloride. Ocean currents such as the Gulf Stream probably are responsible for this.

This discussion only shows you what is going on but not how steel and aluminum makers, pretreatment suppliers, and coatings formulators accommodate these differences. All of the regional conditions we’ve looked at—temperature, precipitation, and corrosivity potential—create a complex and variable demand.

Different regions can have substantially different environmental conditions. In addition, customers have different demands, so there is no simple solution to this complex combination of effects and demands. That is why laboratories around the globe are continuously working to improve performance and to produce a system of metal, pretreatment, and coating that can survive—and thrive—under any number of conditions.

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