What is pre-anodising of aluminium and what do you need to know if you specify projects with powder coated aluminium extrusions? One of the most critical processes to ensure a quality powder coated finish is the pre-treatment of aluminium.
Pre-anodising of aluminium frequently asked questions.
At Superior Paint and Powder Coating, we strive to adopt the most up-to-date standards and processes in the painting and powder coating of aluminium. Here we answer the pre-anodising of aluminium frequently asked questions.
What is pre-anodising of aluminium?
The pre-anodising of aluminium is similar to the anodising process used for the external finishing of aluminium. There are differences between powder coating and anodising, but when used for pre-treatment, anodising offers more durability with superb results in corrosion protection.
Pre-anodising is relatively new in the UK although widely used in continental Europe, especially for the ‘seaside class’ of powder coating to the Qualicoat Standard.
Why is pre-anodising so important?
The European Commission (EC) has proposed to ban the use of (the widely-used) hexavalent chromates used to pretreat aluminium before powder coating. Initially, the cut-off date for applying hexavalent chromates was September 2017.
Following consultation and opposition with many sectors involved in the finishing industry, a four-year extension to the ban looks likely, and an extension of the -implementation date for architectural use will be put back to 2021.
Is pre-anodising and chromate-free better?
Aside from the obvious environmental benefits of anodising before powder coating, there are benefits to this method of pretreatment.
- Improved quality and longevity.
- Exceptional resistance to corrosion.
- Better adhesion of the polyester powder.
- No chromate or other hazardous materials.
- A more uniform paint finish across the entire extrusion.
Is pre-anodising of aluminium a new technology.
No. Pre-anodising has already been used in Europe and the UK with more professional powder coaters adding this process as part of their overall service. Most European architectural finishers operate a pre-anodising or other non-hexavalent chromate or pre-anodising systems.
How is pre-anodising carried out?
The core principle of anodisation applies before the application of the polyester powder. An oxide layer is produced under controlled conditions, and unlike anodising for external finishes, this layer is not sealed.
Anodising does use more electricity as a process compared to traditional pre-treatment methods.
What paint guarantees come with pre-anodised extrusions?
With pre-anodising, you can expect the same extended paint warranties that have been available with polyester powder coated finishes for many years already. Guarantees specific to the use, application and location remain available. The process can be applied to the whole range of current polyester powder colours and powder manufacturers.
Pre-anodising of aluminium creates a durable, attractive and corrosion resistant coating that offers better-looking products, produced in a more environmentally friendly way.