There are many factors to consider when using untreated aluminum outdoors. On this page you will find information about the natural formation of an oxide layer on aluminum, which increases the metal's corrosion resistance, as well as information about the numerous conditions that can negatively affect its corrosion resistance.
Oxide layer makes untreated aluminum more corrosion resistant
When untreated aluminum is used outdoors, a thin layer of oxide forms on the surface. When aluminum comes into contact with oxygen, an oxide layer forms that firmly adheres to the aluminum surface. This layer protects the metal from further attack, increasing its corrosion resistance.
For example, if there is oxygen in the environment where aluminum is located, when the aluminum is scratched, the oxide layer will be restored. At the same time, the layer is insoluble in water and resistant to many chemicals. Finally, the hardness of the oxide layer is equivalent to that of glass. Due to the formation of the oxide layer, it is important to note that untreated aluminum will not retain its original, shiny finish.
Factors to Avoid When Using Untreated Aluminum in Outdoor Areas
If using untreated aluminum in outdoor areas, it is important to know that although aluminum is relatively corrosion resistant, certain factors can affect the corrosion resistance of the metal. Therefore, it is recommended to avoid direct contact of aluminum with:
other metals, such as copper, lead, and iron (especially in wet conditions)
Inorganic acids (such as hydrochloric and sulfuric acids)
Formic acid, oxalic acid and chlorinated solvents
base
Mercury and its salts
Seawater and Chloride Solutions
water with heavy metals
Damp wood types and wood impregnated with copper salts
Alkaline building materials such as fresh concrete
However, due to some of the factors mentioned above, there are various alloys and treatments that can reduce the corrosion that occurs on aluminum surfaces.
Dirt reduces corrosion resistance
Dirt buildup on untreated aluminum surfaces can also reduce the metal's corrosion resistance. Corrosivity is usually reduced due to contamination, keeping the surface wet for longer periods of time. This can be avoided by cleaning dirty surfaces 1-2 times a year, depending on the degree of contamination.
The following options can be used to clean soiled surfaces, listed here in order of least harsh on untreated surfaces. Plain water is gentle on raw metal, while abrasive cleaners are very harsh on surfaces.
boiled water.
Mild soap/detergent.
Solvents such as kerosene liquor or mineral turpentine.
No harsh chemical cleaners.
Polish with wax.
Grind with wax.
Abrasive cleaners.
