Anodizing is a simple electrochemical process that forms a protective coating of aluminum oxide on the surface of the aluminum die casting parts. The rusting of unprotected iron in the presence of air and ater is then inevitable because it is driven by an electrochemical process. The lifetime of the finish is proportional to the thickness of the anodic coating applied. This process has been in vogue since fifty years. Aluminum oxide, as we all know, is a hard, durable and weather resistant substance that protects the base metal. The coating may be either colored by dyeing or it may exhibit bronze tones through diffraction phenomena produced by the coating. he coating is integral to the metal and will not peel or flake. In general anodizing is less expensive than painting with the exception of coil painted products.
Anodizing is particularly preferred for aluminium die casting in high traffic areas where the coating is subject to physical abuse and abrasive cleaners
Anodizing cannot peel off as the coating is actually part of the metal. Anodizing gives aluminum a deeper, richer metallic appearance than otherwise possible. Further, computerized color matching with quantitative, objective color data is now possible. Anodizing is the ideal method for the present day environmental concerns. Though more research needs to be done to determine the total environmental impact of different aluminum finishes, it is evident that anodizing does far less damage. During 1988 the Aluminum Anodizer Council was formed to create and spread awareness about the benefits of anodizing.
The paint manufacturers, driven by selfish interests, were comparing excellent paint to poor anodizing to ward off competition from anodizers. Anodizing which is improperly sealed has poor chemical resistance. Brand new anodizing with a thin coating thickness is nearly identical in appearance to an Aluminum Association Class I anodized finish. Very thin anodized coatings are unsuitable for use on exterior curtain wall or metal roofing. The one distinct advantage of a thicker anodic coating is its durability and longer life. It must be noted that anodized surfaces, like other building components, must be protected from acidic attack during construction activity.
The one demerit may be that after lapse of some years, the anodized surfaces may accumulate dirt and stains that look similar to chalking paint. This chalk can however be removed with a mild detergent combined with an abrasive cleaning technique. A small amount of the upper anodic coating can actually be removed, leaving behind a renewed anodized finish which can last for another few years. This is why anodizers claim that their product is capable of renewal. This method of cleaning often results in a renewed appearance whenever an anodized coating loses effect. Anodizing is ideally suited to storefronts, and wherever a rich metallic appearance is preferred.
Anodized, PVDF and Polyester coatings could all be used on curtain wall, roofing and storefront applications with excellent results. Polyester coatings are formed with unsaturated polyester resins dissolved in styrene. The styrene performs the function of the solvent, with the capacity to respond with the resin and, in the process, contribute to the total solid content. The anodizing chemicals include Cleaning Chemicals, Pre Treatment Chemicals, Anodizing Chemicals, Coloring Chemicals, Electro Coloring and Immersion Coloring and Sealing Chemicals.
There are many options available for finishing aluminum which is why it is such a popular construction material. The question of which finish to apply is not an easy decision because of many options available. With environmental preservation being the crying need of many new developments, there may soon be further options to the already existing range of finishes available for aluminum.
Advantages of Anodizing:
- In general anodizing is less costly than painting with the exception of coil painted products.
- Anodizing is harder than PVDF. Anodizing is superior for aluminum in high traffic areas where the coating is subject to physical abuse and abrasive cleaners.
- Anodizing cannot peel off. The coating is really part of the aluminum casting or metal.
- Anodizing gives aluminum die casting a deeper, richer metallic appearance than is possible with organic coatings. This is because an anodized coating is translucent, and one can see the bottom metal underneath the coating. This translucence contributes to color variation problems, but anodizers are doing a much better job of controlling the amount of color variation than in the past. Computerized color matching with quantitative, objective color data is now possible.
- Anodizing is unchanged by sunlight. All organic coatings will eventually fail due to revelation to ultra-violet light.