Continuous Coil Anodizing
In coil anodizing, coils of aluminum product are unwound through a series of anodizing tanks where the process itself takes place, and then rewound into a coil upon completion. The benefits are many.
- Cost and Production Efficiencies
- Anodized aluminum arrives clean and ready for immediate fabrication. Available in large coils up to 12,000 lbs - less machine downtime for material changes and less scrap.
- Anodized aluminum weighs approximately 60% less than stainless, brass, and copper - more parts per pound.
- The anodic layer is three times harder than the aluminum itself and provides a natural abrasion resistance not found in copper, brass and stainless steel. This means less handling damage during shipping and installation, and better durability down the line.
- Beauty and Versatility
- Anodized aluminum can be roll-formed, stamped, laser engraved, laminated, perforated, welded, embossed, and silk screened.
- Anodized aluminum can be processed to any color in the visible light spectrum, and match any custom need.
- The coil anodizing process ensures consistent color from start to finish and edge to edge of the aluminum coil
- The translucent oxide layer accentuates the rich metallic appearance of the aluminum and does not cover it up like paint. The aluminum oxide layer will not chip, flake, or peel like paint, patina like copper, rust like steel, or weather like brass.
- Sustainability and the Environment
- Aluminum is the most abundant element in the earth’s crust and is 100% recyclable.
- Anodized aluminum and the anodizing process do not contain any volatile organic compounds.
- The Cool Roof Alternative – Lorin ClearMatt® anodized aluminum has a higher solar reflectance index (SRI) value than white painted aluminum.
Steps in the Coil Anodizing Process
The raw aluminum is received containing mill oils, grease, aluminum oxides, and dirt on the surface. These contaminants must be removed prior to the anodizing process. If these contaminants are left on the surface, the anodic film may be pitted and not uniform in appearance, which can cause serious imperfections in the surface especially, if coloring the anodic film. Lorin Industries uses cleaners that dissolve these contaminants while minimizing any metal removal in the cleaning process.
Etching is a chemical process that gives the aluminum surface a very matte and appealing surface quality. Etching in an acid or basic solution prepares the aluminum for anodizing by chemically removing a thin layer of aluminum. The removal of a very thin layer of aluminum will clean up minor imperfections in the aluminum alloy itself. The etching process is also used to control the surface finish of the aluminum allowing for a more consistent panel-to-panel match.
Chemical Brightening is a process that smoothes the surface roughness of the aluminum to achieve a non-directional and highly reflective surface. The chemical brightening process is used where applications such as lighting fixtures or solar concentrators require a reflective surface to capture and distribute light.
Electropolishing is an electrochemical process that brightens high purity aluminum alloys. Reflective tests have shown that electropolished aluminum will be 10% to 12% brighter after anodizing. It will also produce a sharper reflected image on high purity alloys. Electropolishing has been around for a long time, but the only chemical solution that worked was one requiring several pounds of chromic acid. Chromic acid is more costly to waste treat and is also toxic [carcinogenic]. Lorin Industries' electropolishing solutions have been developed without the use of chromic acid. This reflects Lorin’s ongoing commitment to eliminate toxic materials and help protect the environment.
The standard anodizing process uses a sulfuric acid electrolyte. Once the surface is prepared, the anodic film is built from the aluminum itself, and is not a coating. Electrical current is passed through an electrolyte bath in which the aluminum has been immersed. The anodize film is built from the aluminum itself, not applied like paint. The anodic thickness can be tightly controlled and is hard and porous for accepting coloring dyes.
Lorin offers several proprietary anodizing processes designed for specific purposes and aluminum applications. AnoGrip® Type 4 and AnoGrip® Type 5 anodizing processes were developed for applications requiring an aluminum substrate with superior adhesive bonding characteristics. These processes are environmentally safe unlike chromate conversion coatings that have been known to cause cancer. ClearMatt® with Adhere® was developed for customers that require a superior anodize quality finish on the top-good side and has an excellent adhesive surface on the other side.
The anodizing process provides the opportunity for an artist’s pallet of colors in the final product. Anodic films are well suited for several coloring methods.
Absorptive Dye Coloring - This coloring process employs organic or inorganic dye stuffs. The aluminum oxide layer is a very porous structure and will absorb staining materials. For example, any colored fabric dye can be absorbed into the aluminum oxide layer. These dyes offer vibrant colors with intensities that cannot be matched by any painted metal system in the market. The color possibilities are endless.
Electrolytic Two-Step Coloring - After an anodize layer is built, the metal is immersed in a bath containing an inorganic metal salt. Electrical current is applied which deposits the metal salt in the base of the pores. The resulting color is dependent on the metal used and the processing conditions. The process offers color versatility and is the most technically advanced coloring system available.
Lorin’s ColorIn® Portfolio of products uses the electrolytic two-step coloring process. This process offers exceptional fade resistance and is very suitable for exterior applications.
The unique color matching capabilities of Lorin Industries offers a range of options not available through other coil anodizers.
This is the final step in the anodizing process. It closes the pores in the anodic film, locking in colors and creating a surface resistance to staining, abrasion, and color degradation.