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The Coil Coating Process: Prepainted Steel And Aluminum

Coil coating refers to the process of creating prepainted steel and aluminum. Prepainted steel or aluminum can be found in a high number of household products. From refrigerators to air conditioners and construction material, prepainted steel can be found everywhere. Different coatings can be applied for different demands.

“In some coatings, you are going to need more exterior environment weathering, flexibility, and more impact resistance than you do with other coatings,” says Aaron Small, Corporate Vice President at Kloeckner Metals U.S. and President of the National Coil Coating Association (NCCA). “If we’re going to do roofing and sidewalls, we would often choose either a fluorocarbon, siliconized polyester, or modified polyesters.”

Coil Coating: The Basics

Coil coating is how the coating material is applied to the strip of steel or aluminum. A coil of metal sheet is continuously fed into the process which is controlled via accumulators at each end of the line. They take in a bare coil of metal at one end and let out the finished product on the other end. In the middle, the coil coating process is applied.

“What we do is actually referred to as high-speed, continuous coil coating,” Small says. “What makes high-speed, continuous coil coating possible is the non-stop application of the cleaning, the treating, the coating, the curing, and potentially the leveling, while the sheet is flat, all in one high-speed path through a coil coating line.”

The Key to Coil Coating

The key is being able to maintain a constant speed of the strip through the process. The accumulators allow this by letting the middle of the line to continue running at the prescribed rate while new metal is added at the decoil end, or the finished product is removed from the recoil end of the line.

“You don’t have starts and stops,” Small says. “This allows our coaters to consistently clean, treat, seal, apply a paper-thin coating, cure it evenly, and cool it back down without burning the metal or the coating.