Anodized paint is a somewhat misleading term. Normal paint is never anodized, but some paints give an anodized appearance to surfaces. To further complicate things, when an anodized surface is colored, it isn’t actually painted, it is dyed. Anodizing is a process done to metal surfaces that makes them more corrosion- and wear-resistant. This is achieved through increasing the overall thickness of the oxide layer present on the surface of most metals. This creates a buffer between the environment and the actual metal underneath.
Anodizing can only be done to metal surfaces, which makes anodized paint an impossible item. Generally, a paint that advertises as anodized will simply give the appearance of an anodized finish. This typically means that when the paint is dry, it will look like colored metal rather than paint on a metal surface. In most cases, the anodized paint only gives the appearance and not the other common properties of an anodized surface.
The anodizing process gives a new set of chemical properties to the metal surface. This is done through controlled passivation. An electrical current is applied to the material, which encourages oxidation on the surface. If done correctly, this will result in a porous, low-friction and corrosion-resistant layer of the metal underneath. If done incorrectly, it results in increased corrosion rates and weakened materials.
In addition to the protective properties, anodized metal will take on new color extremely well. The anodized layer is porous, meaning it is filled with little holes and chambers. When color is applied to the surface, it soaks in just as if the surface was made of cloth or wood. When the color hardens, it has become part of the anodized layer. As a result, adding color to anodized metal is a form of dying rather than painting.
Since it, in effect, becomes part of the metal, anodized paint has a very distinct appearance. For the most part, the colored anodized layer looks like the metal is simply a different color. The sheen and texture of the metal are nearly the same as without the anodized layer. This is because some of the metal is still visible along with the color, but the distinctions between the metal and color are so small that they can’t be seen with the naked eye.
A second form of anodizing actually gives the metal a unique appearance. This layer will reflect light differently than a normal metal, often leaving a satiny or refractive surface. After the metal is dyed, it retains the effect but displays the new color. This is also an effect mimicked by anodized paint.
By M. McGee