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We have received enquiries from customers manufacturing black anodised aluminium outdoor products who are concerned about the colour fading in beach areas or other high temperature environments. This is an understandable concern, but anodised aluminium is not the same as painted or powder coated surfaces in this respect. However, it is true that anodised aluminium can appear to “fade” in outdoor environments. This has led to questions regarding the long-term effectiveness of anodising as a metal protection method.
The positive news is that the “fade” you see is not actually a result of the anodising process itself, but rather due to microscopic surface contamination and environmental abrasion affecting the appearance of the anodised layer. Please refer to the illustrations provided for further details on the reasons for this.
Structure of Anodised Aluminium
Anodised aluminium is a type of aluminium that has been subjected to an electrolytic process, during which a layer of oxide is formed on the surface. This process creates a porous oxide layer on the surface of the aluminium, allowing dyes to penetrate and result in deep, rich colours. A barrier layer is also formed at the bottom of the pores, protecting the underlying metal. As long as the anodic oxide layer remains intact, the colour will remain stable.
Surface Contamination and Dull Appearance
With time, the pores in the anodised layer attract dirt, dust and contaminants from the environment. In high-traffic or outdoor environments, these contaminants can build up and result in the surface appearing dull. This can cause anodised aluminium to appear faded when, in reality, it is merely dirty.
Damage from Abrasive or Harsh Cleaning Products
Another common issue is the use of acidic or alkaline cleaning solutions and abrasive cleaning products. These products can react with the anodised layer, leaving a residue in the pores. This type of chemical contamination can alter the way light interacts with the surface, creating an uneven or washed-out appearance.
Corrosion Due to Environmental Exposure
The anodised layer is susceptible to deterioration in harsh conditions, including exposure to salt water, acid rain or prolonged humidity. Rain and harsh chemicals can penetrate the anodised surface, leading to deeper corrosion, staining and structural degradation. This results in a mottled, speckled appearance, indicating a damaged surface.
How to Repair and Protect Anodised Aluminium?
The anodised layer itself is characterised by its permanence; therefore, the key to maintaining its visual appeal is to ensure it is properly cleaned and protected.
Use of sealing and protective coatings: At the production stage, the application of BROMOCO's AA-1665D anodised aluminium protective coating, specially developed for anodised aluminium, helps to counteract the above problems and prevent future environmental damage.
Regular cleaning with mild products: It is recommended that cleaning be carried out regularly with mild products. Use of pH-neutral detergents and soft cloths or brushes is advised for the removal of dirt and contaminants without causing damage to the anodic oxide layer. We recommend BROMOCO's ERW-BD Biodegradable Degreaser as a gentle, efficient and neutral preparation and cleaning product. This product can be used as a standardised preparation agent before BROMOCO applies sealing coatings, as well as for daily cleaning. It requires only a fresh water rinse after cleaning, which is quick and easy and reduces maintenance costs.
Need help choosing the right solution?
If you are dealing with issues related to the protection and maintenance of your metal products and want to ensure that your products stay looking new for years to come, contact us today for tailored advice and application instructions.
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