by John Brana August 14, 2012
Preparation is generally required for any aluminum item that is to be anodized, regardless of shape or size. Before the metal can be anodized, the aluminum must be cleaned well with a strong caustic formula, such as sodium hydroxide. It may need to be heated up to 145 degrees to extract any oils or residues to the surface. Once the metal has been thoroughly cleaned with the caustic solution, it should be rinsed well with deionized water and allowed to dry.
Aluminum anodizing begins when the metal is placed into a solution of acid, while attached to electrodes. These electrodes are attached to an electrical source that sends alternating currents of energy to the aluminum. On average, the voltage used in the anodizing process is between one and three-hundred volts, with the average volts being between fifteen and twenty-one. Sulfuric acid is a commonly used method for anodizing aluminum. This involves coating the metal in a fifteen percent solution of sulfuric acid. In the acid solution, a cathode is also placed while connected to a negative terminal. The positive terminal should be placed on the aluminum that is to be anodized.
On average, this process of anodizing aluminum requires five amps of current at a seventy degree temperature per square foot of the aluminum. When the current is turned on, it releases CO2 molecules which combine with the metal to form an Al2O3 aluminum oxide coating. Some pieces of aluminum are hard-coated, which leaves a darker finish. When pieces of aluminum jewelry are hard-coated, they are not suitable for dyeing. To hard-coat aluminum, a fifteen percent sulfuric acid formula is lowered to 32 degrees Fahrenheit. The anodizing process requires twenty to one-hundred twenty minutes at twenty-three to thirty-seven amps, depending on the thickness of the coating. Due to the thickness of the aluminum, hard-coating aluminum generally results in a tougher surface area.
Another method of anodizing aluminum uses a less corrosive acid, chromic acid. Since there is less corrosion than there would be using sulfuric acid, the metal is generally easier to rinse. When chromic acid is used to anodize aluminum, it lowers the risk of metal fatigue that can occur during the sulfuric acid or hard-coating methods. The biggest advantage to using chromic acid is that it’s easier to rinse more complex designs. On average, this method of anodizing requires an amp of four per square foot at a temperature of sixty to seventy-five for about ninety minutes.
John S Brana, based in San Francisco, is the founder of John S Brana Handmade Jewelry with over two decades of expertise in crafting distinctive handcrafted pieces. Transitioning from a finance and banking career in 2004, John manages everything from design to marketing. His modern, urban-inspired creations have graced fashion editorials, resonating with stylish, adventurous enthusiasts who value exquisite craftsmanship and luxury. Every piece narrates a distinct tale, mirroring the wearer's individuality.
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