Paint Vs Anodised Finish: Cost, Colour, Durability and Environmental Considerations

Anodizing and painting are two of the crucial choices accepted by architects for bringing colour to the external surfaces of their projects. The main factors determining these choices include cost, aesthetics, durability, environmental impact and colouration.

Anodizing refers to the growth of a coating of aluminium oxide from aluminium by passing an electric current via an electric acid bath in which the aluminium is submerged or dipped. The thickness of the coating and surface features are controlled with much care and accuracy to meet the specifications of the end product.

When painting is compared to anodizing, the difference is determined by aesthetics, looks and hardness. The benefit of anodizing is the authentic metallic look that can be achieved. Anodizing creates a look that ranges from translucent to transparent, resulting in a hard coating on aluminium. There are various advantages of Anodizing. Some of them are:

Advantages of Anodizing

• Generally, anodizing is less costly than painting, except for coil-painted products.
  
• Anodizing is harder than PVDF (Polyvinylidene Fluoride, a factory-applied, chemical-resistant, resin-based coating made of pigmented particles that support an extensive range of colours with a matte finish).
  
• Anodizing is harder than FEVE (Fluoroethylene vinyl ether), a resin-based powder coating.
  
• Anodizing is superior for aluminium in high-traffic areas where the coating has to endure abrasive cleaners and physical abuse.
  
• It is not possible for anodizing to peel off. The anodized coating is part of the metal.
  
• Anodizing provides aluminium with a richer and deeper metallic appearance than organic coatings. The reason is that the anodized coating is translucent, and the base metal is visible beneath the coating. Such translucence results in problems of colour variations. Yet, anodizing functions much better in controlling the quantum of variation of colour than previously.
  
• In most anodizing centres, one can expect to find a computerized matching of colour using objective, quantitative colour data.
  
• Anodizing is not impacted by sunlight. In contrast, every organic coating will ultimately fail due to sunlight exposure.

Durability of anodizing and painting

With time, the impact of rain, corrosion, UV rays and inclement weather can wreak havoc on coated materials. Anodized and painted surfaces react differently towards such harsh conditions.

Painted services offer better resistance to mortar staining, acid rain and corrosion than anodized surfaces. But this also depends on the paint quality, ranging from a few months to nearly 20 years.

The durability of the surface finish also depends on a construction schedule that may be rushed. If the building is on a rushed schedule, caution must be taken when using anodizing. If any masonry mortar is caught in the anodized surface, the surface finish may be damaged beyond any scope of repair, and the only remedy could be replacement. In such cases, painting will endure much more than anodizing.

The location of coated materials also impacts durability. Surfaces subject to abrasive conditions will be better suited to anodizing than paint.

After several years, anodized surfaces may build up stains and dirt that resemble chalking paint. Such chalk can be removed using a mild detergent with an abrasive cleaning technique. It is claimed that anodizing is a renewable process because a part of the coating can be removed, and a renewed anodized finish can last for 20 more years.

Cost of painting and anodizing

Powder coating is the cheapest since a single coat will suffice. Opting for one of the few colours possible with anodizing becomes more affordable than liquid paint. But, if you request a specific colour in anodizing, it can prove more costly than paint.

Paints & Powder Coatings feature a notable cost benefit over a lifetime of use when repair and upkeep are needed. Touch-up is fast and easy through the use of high-quality paint, particularly in areas with high traffic, such as commercial buildings where people and materials are going in and out.

In contrast, touching up the surface with anodizing is impossible, but it will need a total replacement, which proves very expensive. Warranty is also a cost factor that must be considered.

Warranties on paints can range from zero to forty years for colour and gloss retention, based on location and kind of coating. Anodizing warranties may vary from 5 years to a lifetime based on criteria like filiform corrosion.

The choice of colour palette

Regarding the colour options available to architects, painting has an obvious benefit over anodizing. Anodizing is limited to a few ranges of colours, mostly falling into five categories: Black, Dark bronze, Light bronze, Champagne and Clear.

In contrast, with paint, the palette of colour is almost unlimited. Any colour can be matched only with a few exceptions. Maintaining a consistent colour, batch-to-batch, and day-to-day is much easier with paint.

To maintain the consistency of colour in a project, it is vital to understand the standards of the industry that define colour variations. Matching the colours of paints requires close monitoring, experience, and skills.

At the same time, paint does not offer perfect colour consistency. Contractors need to apply the coating at the same place at the same time to reduce the risk of colour variations caused by different conditions of application and batches of paint.

Environmental issues

These play a significant role in the specification of materials. In general, paint is a hazardous waste. As such, paint users face more issues that need to be addressed because of environmental regulations. Painting releases harmful substances like VOCs (Volatile Organic Compounds).

The role of anodizing is less prominent but appears to be more compatible with the current environmental concerns. From most points of view, anodizing does less damage to the environment.

Municipal wastewater treatment facilities can use the chemicals released by anodizing.  The anodizing plant releases an effluent containing aluminium sulphate, which helps improve the efficiency of solid settling in certain plants for wastewater treatment. It does not release any ozone-producing solvents and does not involve the use of any hard metals.

In sum, these are some of the differences between the use of painting and anodizing procedures on external surfaces like aluminium walls.