Aluminium Powder Coating Treatment

Aluminium clad windows are increasingly becoming the smart choice for homebuilders. Environmentally friendly, durable, weather-resistant and easy to maintain, aluminuim has therefore become a popular choice. Aluminium is equipped with very good natural corrosion protection as a thin transparent oxide layer forms already on the blank metal surface. Based on qualitative considerations, the surface of aluminium profiles is treated and protected by colour coating (powder coating) or anodising oxidation. Aluminium Powder coating is hence, a standard proceedure which is explained below.

Internorm windows and doors have an extensive range of aluminium clad windows and doors which go through this standard proceedure in their making.

What are the advantages of Powder-coating?

Powder-coated aluminium facades have been used in architecture for more than 20 years. With proper care they can withstand demands of environmental and climatic influences.

With powder coating, an electrically charged paint powder is applied to aluminium profiles and afterwards burned-in (approx. 180°C). Through this, a closed polyester resin film is formed which is characterised by high resistance against environmental influences and mechanical stress.

Weather resistance is measured through laboratory tests along with short term as well as long term weather resistance tests. With long term tests, coated aluminium profiles are exposed to natural UV radiation and are checked and evaluated in regular intervals for residual gloss and colour changes.

Colour coated aluminium profiles are also checked for resistance to chemicals (e.g.: mortar, cleaners etc.) and also offer relevant protection for these. Electrostatic powder coating is therefore, environmental-friendly technology as it completely avoids any solvents. Correct cleaning should be carried out twice per year or depending on the degree of dirt, more often.

What is the Set-up of powder-coated surface?Diagram showing the composition of the layer of the powder coating of aluminium

  • Suitable pre-treatment is the most essential pre-requisite for a lasting coated metal surface. Degreasing and staining remove dirt and the natural aluminium oxide layer.
  • Above this, a thin yellow or green chromite layer is applied to provide a good adhesion and prevent infiltration on cutting edges or with paint damage.
  • The powder layer is applied on top of the chromate layer and burnt in. The thickness of the powder coating is approx. 50 – 150 ?m depending on profile geometry and colour.

What are the Quality criteria of a powder coated surface?

Powder coating is an industrial coating which is carried out according to the quality criteria of the GSB International (GSB AL 631). This provides the quality label, licensing and regulations for the coating of building components and pre-treatment of chemicals.

Evaluation of decorative appearance (colour, structure, etc.) is rather made without the use of any tools. The following viewing distances apply for quality assessment:

Outside viewing with 3 m distance and inside viewing with 2 m distance

Gloss level

The required gloss level of surface with powder coating depends on the type of colours-(Standard/Special) used on the aluminium surface. Standard colours manufactured with matte surface require about approximately 25±5% gloss level. Whereas the special colours according to the RAL chart manufactured with gloss surface require about almost 80 to 95% of gloss.

What is HM (HWF)?

HWF is highly weather-resistant and fading resistant powder coating. Here, the surface is treated with improved gloss and colour retention properties. This characteristic is available in limited pigments due to certain limitations. It has lower chalking tendency. Therefore, the high-quality coating of the HMF surfaces result in high value retention of property. In addition, HMF coated aluminium products have been tested in extreme weather conditions in South Florida.

Furthermore, this coating is certified and approved by the QUALICOAT quality label which is an international association of product quality for liquid and powder coatings on aluminuim for architectural applications.

The above explained standard and a quality proceedure is consequently, a testimony of the way powder coating is done on Internorm’s aluminium clad windows and doors.