Bright Dip Anodizing
Bright dip anodizing is an electro-chemical process utilized to improve both the aesthetic and functional properties of aluminum components. Though these processes work with other metals as well, aluminum responds the best to this particular treatment and as such is the most common. Hardening and shining the product, bright dip anodizing of aluminum is popular in industries where the products are to be both functional and aesthetically pleasing.
A wide variety of products can be subject to bright dip anodizing, including products such as camera and mp3 player cases, food and beverage containment, cookware, architectural accent pieces, sports equipment, framing and automotive construction as well as more industrial components such as manufacturing and plant equipment.
The popularity of this process as opposed to alternatives such as electro-polishing and coating can be attributed to the unique benefits afforded by the bright dip process. Though the results vary, bright dipped aluminum has a glossy, high luster appearance and may even result in a reflective, mirror-like finish.
This gloss is achieved through bright dipping without leaving deposits on the surface of the part as do many other finishing processes. Depending on the grade of the aluminum, the process is also very fast, taking as little as 30 seconds to complete. The most suitable aluminum alloys for bright dipping are 5357, 5457, 6063, 7016 and 7016.
Bright dipping and anodizing are actually completed in two separate steps with bright dipping pertaining to the aesthetic of the metal and anodizing improving hardness and resistance to corrosion and wear. Bright dipping occurs first as a pretreatment to the anodizing process. A relatively simple concept, the aluminum component is dipped into a double walled, stainless steel tank filled with the brightening solution and heated to above 200 deg F.
The solution is a chemical bath that smooths the surface on a microscopic level, resulting in the desired sheen. Though mixes will vary, the basic composition involves phosphoric/nitric acid. Acetic and sulfuric acid are common additives. Due to the use of harsh chemicals and high heat, the bright dipping component of this total process requires careful calculation and is regulated by worker safety and environmental laws. The bath should be carefully racked and agitated in a rocking motion to avoid spotting due to gaseous bubbles on the surface of the part.
Other considerations include proper ventilation and a warm rinse tank. Once the desired shine is achieved, the part must be washed several times prior to anodizing. There are two main ways that metal is anodized: bath anodizing and anodic painting. The more common of the two is bath anodizing, which involves fully immersing the metal in a tub of the anodizing acid.
Once the metal is submerged, a power supply is turned on that introduces an electrical current to the bath. The resulting reaction changes the surface of the metal into a thin film of metal oxide. The total results are increased corrosion and wear resistance as well as cosmetic enhancement.