Aluminum is a versatile and durable element, but as with many other industrial metals, it can begin to deteriorate after time and extensive use. Long term exposure to weather conditions can cause irreversible damage to aluminum. Surface deposits resulting from a number of industrial processes can also affect the aesthetic qualities and function of the metal. To ensure that aluminum remains functional, experts generally recommend cleaning it on an annual basis. Maintenance can be performed through a series of the following chemical processes.
The Importance of Solvent Treatments
In time, untreated aluminum will develop an oxidized “chalky” coating, which protects the metal from pollutants and environmental weathering. A clear base lacquer typically prevents the oxidized coating from forming, although an accumulation of dirt from processes can be expected. Residues from packaging and transporting can impact the function of aluminum. Oils and grease from industrial use can also leave residues on aluminum. A soil “test” may involve either a white cloth wiping method or immersion of aluminum surface in water. The latter process will typically indicate whether grease or hydrophobic pollutants are present, depending on whether the surface wets evenly or breaks up. To maintain aluminum siding, windows and doors with minimal damage or residue, industrial aluminum experts typically suggest applying a solvent cleanser. The cleansing should be practiced on a yearly basis, as aluminum that is not maintained will develop irreparable corrosions.
Solvents are effective in removing grease stains from aluminum. Trisodium phosphate (TSP), for example, can be prepared when dissolved in water. This is an alkaline solution that is commonly used as a flux. Fluxing, a process used in preparation to welding and brazing, may actually leave behind deposits which should be rinsed in a timely manner.
Alkaline and Non-phosphorous Treatments
Alkaline cleansers, which exist in numerous chemical formulas, are effective in removing and dispersing aluminum surface soil. The reasonable cost of the equipment and chemicals used in this process also make it a widely used method in aluminum cleaning. The degree of alkalinity in each solvent depends on the amount of soot present on the aluminum; they range from abrasive cleansers to neutral solvents. Chemical compounds generally found in alkaline cleansers include sodium polyphosphates, which contributes to water softening.
Non-phosphorous cleansers are also used to clean aluminum. These solvents are applied to maintain the metal’s patina. The solution (it’s alkalinity, specifically) may be used to etch the aluminum or to mill the metal parts for applications. Typically, this and the aforementioned solutions can be applied using a spray tank, a pump spray or a pressure wash, but this depends on the type of aluminum fixture to be maintained and the amount of soil involved. Alkaline cleansers, in particular, may be applied to aluminum through steel tanks and through immersion by a bath method. A formulation of a typical bath include acid bright dips and nitric and hydrofluoric acids.
Acid and Vapor Degreasing Treatment
Although acid cleansers are less effective in the removal of soil than alkaline cleansers, they are effective in the removal of oxides. A common formulation includes orthophosphoric acid, water, and butyl and isopropyl alcohol. Fluxing, which may leave behind residues, can be dissolved with acids, and formulations that include nitric and hydrofluoric acids are considered effective. Nitric acid, for example, is typically used as a chemical application in the removal of pollutant products on aluminum that are a result of chemical processes. Acid treatments are usually applied to clean larger surfaces or industrial exteriors that are in the preparation stage for painting or finishing. There are also acidic formulations that are applied to aluminum with the purpose of preventing oxidation residues.
Vapor degreasing is another method suitable for aluminum cleansing. It is used to prevent or restrict moisture accumulation via condensation. Generally, water exposure can result in hydrolysis hydrochloric acid, which can ruin the exterior of the aluminum, which is why this cleansing method is efficient.