Surface Treatments & Finishes for Fenestration Systems
Fenestration systems made out of aluminium alloys require specific surface treatment to optimize their functionality and increase their durability. Surface treatments generally refer to altering the constitution of a product’s surface; this enables it to interact with an adhesive, ink, coating, paint, etc., in order to create a strong bond between the two. The reason for controlling the chemical composition of the surface layers is to enhance the adhesion properties, simply to make them resistant to damage and corrosion or to improve the products’ appearance. Therefore, surface treatment constitutes a very fundamental aspect of product manufactures before they are assembled.
ALCOI provides a wide range of customized finishes and colour choices in fenestration systems. There are various methods by which a coating can be applied as a surface treatment to increase the performance of a material.
Anodizing
Anodizing is an electrochemical process that enhances aluminium’s natural oxide surface by forming an even more durable anodic oxide surface that can accept various colours. In the anodising process, extruded aluminium parts are immersed in an acid electrolyte bath. An electrical current is passed through the solution following a series of cleaning, rinsing and etching steps. Dyes can subsequently be applied as the final step.
Usually, a thickness of 15 microns and a minimum of 18 microns for saline atmosphere and coastal areas is used in this process. The resulting oxide layer is extremely hard and corrosion-resistant, thus providing outstanding durability and low maintenance costs. Owing to these properties, anodising is considered a popular finishing choice for applications in architectural products, home appliances, furniture, boats and sporting goods, and personal electronics.
Powder Coating
In powder coating technology, fine particles of organic resins and colouring pigments are electrostatically charged and sprayed onto the product’s surface. The spraying process can either be done manually or by automatic horizontal and vertical lines of paint. These charged powder paint particles adhere to the surface and are retained until melted in the polymerisation furnace to form a homogeneous and durable coating. The products are kept in this furnace for 15-20 minutes at 160-210°C, depending on the type of powder paint. Under the influence of heat, the powder particles soften and form a continuous uniform coating.
Generally, powder coating uses pure polyester powder of “Jotun/AkzoNobel” or equivalent in minimum 50-60-micron thickness. It is an effective surface treatment process to create a strong, durable, protective and decorative coating.
Sublimation
Sublimation is a process that uses a polyurethane base coat on which special heat transfer inks from “Decoral, Italy” are transferred to provide a wood grain effect or other special effects. The profiles are provided with masking tapes for safety against external scratches, which the contractor removes at the time of handing over.
The sublimation process has four primary steps — First, a film with the decorative pattern is wrapped around the aluminium profile. All the air is then removed from the space between the film and the profile. This ensures that the film stays firm against the coated aluminium. The wrapped extrusions are placed into a curing oven. As they heat up, the wood grain pattern gets transferred from the film to the aluminium. Finally, the extrusions are pulled out of the oven and are allowed to cool down after the film is removed.
The surface treatment of aluminium fenestration systems is mainly done for corrosion resistance and the purpose of aesthetics. Not only does it provide the profiles with superior qualities and functionalities, but it also plays an enormous role in extending the life of the products. Designing spaces with fenestration systems that are extruded from light aluminium alloys have become increasingly common today. Hence, choosing an appropriate surface treatment and finish is really important to ensure high overall performance and a fine appearance of your fenestration system.
