The benefits of high solids coatings for railroad tank cars
According to the American Association of Railroads, there are currently over 380,000 railroad tank cars in service. The vast majority of these cars are not owned by railroads, but leased by private customers who use them to transport their products. Many of these lessees encounter a similar problem with their tank cars. It has to do with the percent solids of the coatings used to protect them. For a refresher on the percent solids of a coating, check out this post we wrote on 100% solids coatings.
Due to the cylindrical shape of tank cars, and gravity, it’s more difficult to achieve the desired film build on the top of the tank, often leading to an unevenly applied coating. During its service life, this top portion of the car will be prominently exposed to repeated rain and harsh sunlight. Eventually, the stress leads to a problem known as “blooming,” or rusting on the top of the tank car. “Redheads,” as cars with this problem are known in the industry, are a good indication that something went wrong during the coating application process.
This problem can be avoided by using coatings with a higher percent solids. With fewer solvents flashing off, the coating dries more quickly and it’s easier to achieve high film builds on the top of the tank. The end result is a coating that’s more evenly distributed over the entire tank car. But that’s not the only benefit of using a higher solid coating.
Coatings that contain higher solids by volume also allow a shop to purchase less material to cover a given square footage. If a typical 60 percent epoxy has a theoretical coverage rate (where no loss occurs during the application) of 190 square feet applied at 5 mils DFT, an 80 percent solids version would have a theoretical coverage rate of 260 square feet applied at 5 mils DFT. The result is 27 percent less product that’s capable of covering the same area.
Higher solids coatings also significantly cut down on the amount of volatile organic compound (VOC) and hazardous air pollutant (HAP) byproducts. Lower levels of evaporating solvents mean fewer VOCs are released into the atmosphere, and into the shop. For large-scale operations VOCs can add up quickly, making cutting back on these substances necessary to avoid fines. Tighter regulation of VOC outputs may increase the importance of alternative choices in the near future.
Some attempt to completely take VOCs out of the equation with water-based coatings. But this approach also has its drawbacks. They take longer to cure, potentially causing backups in the shop. Properly accounted for, this strategy can be a viable solution. But like we’ve talked about before, the best solutions draw on a number of key features.
A balancing act
Ideally, the right product will offer a balance of these key features. It should have relatively high solids by volume for film build, and low VOC output to ensure that the shops where it is applied adhere to environmental standards. It should be able to be applied efficiently and in a timely manner. And of course, it must be a cost-effective solution. Click the link read more about our railcar coatings, or visit our tank linings page for more on linings.