At Novelis, we specialize in a variety of continuous treatment processes to ensure the best final product for our customers. From heat treatments to conversion layers and coil coating, Novelis continuous treatments work to assure we are tailoring products to our customers’ every need.
Conversion Layer & Coil Coating
Aluminum Coil Coating & Conversion Layers
One of the benefits of aluminum is the ability to apply special surfaces and unique characteristics. With the help of conversion layers and coil coating, Novelis supplies aluminum in a variety of textures to meet every customer’s needs.
Aluminum Coil Coating
Novelis pre-painted aluminum sheets and decorative aluminum finishes are produced using an aluminum coil coating process. Coil coating is a continuous process where the aluminum substrate is degreased, chemically pre-treated and coated. The paint, an organic solvent or water-borne system, is applied through rolls. Compared with a post-painted material, aluminum coil coating can improve productivity and quality, while decreasing cost and environmental emissions.
Novelis continuously works with customers to assure that the end product is tailored to their needs.
The steps in the Novelis production process are:
- Tension Leveling: Tension leveling works to guarantee an absolutely flat product.
- Cleaning and Pre-treatment: During this step, chemicals are added for cleaning and oxides are removed, as are dirt and lubricants. Our process ensures that cleaning is more efficient than conventional technologies, reusing water and cutting consumption levels. From there, pre-treatment occurs by adding a conversion layer on the aluminum strip.
- Coating: Paint is applied using rolls. All paint systems are geared to match the requirements of the application. There are two primary types of coating: decorative and functional.
- Curing: Depending on the paint system, the curing temperature lies between 200° and 300°C. In order to protect the environment, the solvent vapor is used to heat the oven without gases escaping from the closed system.
- Quality Control: By means of a computerized process involving highly sensitive electronic measuring devices, the paint quality is constantly controlled. Novelis examines each product for color uniformity, coating thickness, gloss, paint hardness, paint adhesion and forming characteristics.
- Protective Film Application: A protective film is applied to some of our products, based on customer need. The protective films differ depending on the particular product and often carry additional information such as coating direction and brand details.
- Further Processing: In this step, painted strips are stored for processing, and Novelis cuts the sizes of coils per the customer’s request.
Novelis has two solutions for conversion layering. The choice depends on the subsequent processes the customer chooses to use:
Thin Anodized Films (TAF)
Within a special process, a thin artificial oxide layer is applied to the material by continuous strip anodizing, which then “grows” into the aluminum surface. The oxide layer consists of a barrier layer and a filament layer. It is impermeable to oxygen and water vapor and it also resists corrosion. The compact porous structure of the material surface makes it especially well-suited for adhesive bonded joints. TAF is often used for inner panels, body-in-white applications and traffic signs.
Pre-Treatments on a Titanium Base
With this method, aluminum sheets can be pre-treated on a titanium basis (titanium fluoride, titanium/zirconium fluoride, zirconium fluoride). The natural aluminum oxide layer is completely removed and then, during a complex chemical reaction, replaced by a chemically stable surface with a thickness of only some nanometers. The main advantages of this process are improved adhesive bonding performance within the guaranteed storage time due to the inert surface.
Aluminum Heat Treatment
Novelis aluminum alloys are available in various combinations of strength and formability, depending on their composition, processing, heat treatment, cold work and gauge. The formability of the aluminum sheet we produce varies considerably depending on the alloy and temper of the metal.
Heat treating aluminum and aluminum alloy materials comprises a number of different thermal operations, which are used to achieve specific properties for further processing or service behavior. A thermal cycle is characterized not only by time and temperature, but also by heating and cooling rates.
Our aluminum alloys are subjected to a series of processes to ensure the ideal qualities for their specific application:
- Annealing (Recovery and Recrystallization)
- Solution treatment
Novelis operates three continuous annealing lines with air cooling and water-spray cooling systems for the heat treatment of aluminum in strip flotation furnaces. Two lines are located in Europe and one in North America.