First, a bit of history …
The pre-paint industry started in the 1930s and arose from the need for painted strips used to make venetian blinds. Wide coils were painted in flat form, and the coils were then cut into the strips to form the blind slats.
Over the years, the coatings have evolved to allow many other industries to be able to manufacture products using pre-painted metals.
Over the years, the industry has grown sizably. According to the The National Coil Coaters Assn., over 4.5 million tons of steel and aluminum are coated annually in North America and approximately and 5 million tons in Europe.
We’ve seen painted metals being used throughout industrial applications. It’s common knowledge that a part can be formed out of metal and then the part can be painted after it’s formed. There are a variety of coatings than can be used to apply paint, post-forming, including powder coating, dip coating and spray coating. But did you know that in some instances, the paint is applied before the forming takes place?
Post paint applications are those in which coatings are applied post-forming of the part, and pre-paint applications are those where the paint is applied to the flat coil before any cutting or forming takes place.
Pre-paint coatings must not only withstand the rigors of the forming processes, but they are also designed to be able to stay on the part and survive all sorts of real-world applications. The coatings used for pre-paint are considered “performance coatings.’
In other words, they are designed to perform. Some examples of performance coatings include food can liners, designed to protect the food from the can, or roof coatings, designed to withstand sun exposure over many years of direct exposure.
Pre-painted metals are produced at high speeds in high volume.Unlike spray or powder coating, the process of applying the paint does not lend itself to small volume runs or lots of complex color changes.For this reason, many of the industries that already use pre-paint tend to be high volume production.
The substrates used for pre-painted metal can be cold rolled steel, galvanized steel, hot rolled steel, galvalume, stainless, and aluminum.Basically, anything that can be manufactured in coil form is a possible input substrate for painting; however, the costs of some substrates generally keep them from being widely used.Most of the metal coatings that are coil coated range between .008 to .125 thick. The widest coil that can be painted is around 72” wide.
The application process is continuous and runs at line speeds of between 300 to 900 feet/minute. Both sides of the coil can be painted simultaneously, and up to three layers of paint can be applied on one side (on some paint lines). Coils can be coated with two different coatings on each side (2 colors for example, or one smooth and one textured coating on either side). The coatings on either side can also be applied at varying thicknesses.
What Are Common Grades of Metal that Can Be Coated?
For aluminum, one of the most common grades used for coated applications is 3105 H24 and H14.
For carbon, common grades are found in Colorklad such as these.
Pre-painted metal is a value-added product. Complex supply chains are built to support the selection of the coating, the application of the coating, and all the logistical concerns.
If you find that you can’t meet your cost savings goals, or if you are struggling with overall throughput on your paint line, contact Ryerson to talk about the possibility of a conversion to pre-paint.
About the author
Lisa Shelton has worked in the coil coatings industry since the early 1990s. She’s held positions at the coil coaters, service centers, and the paint companies who manufacture the coatings. With over 28 years of experience, Lisa has helped companies that need to source existing pre-paint, as well as companies that are interested in using it for the first time.