Aluminum is a lightweight metal with a specific gravity of 2.7, regarding one-third the density of steels (7.8). This is why aluminum alloys are widely used in the construction industry, the mechanical industry and the transport industry (automotive, aeronautics, naval, etc.) in order to lighten structures.
Aluminum and its alloys also have a high thermal conductivity compared to steels, which makes them excellent materials in heat exchange devices (radiators, exchangers, refrigerators, air conditioners, etc.). In addition, their good electrical conductivity and their low weight allow them to be widely used for the manufacture of electric cables, in particular cables of large sections.
The third characteristic of aluminum is its ease of implementation under conditions of temperature and reasonable mechanical stress (casting, spinning, rolling, stamping, etc.). Combined with a good aptitude for surface treatments, this property makes them very interesting materials for forming complex mechanical parts with decorative functions (doors and windows, lighting, street furniture, household items, etc.).
Aluminum is also one of the metals which have good resistance to corrosion and can be brought into contact with various environments: rural, urban or marine atmospheric conditions, acid medium in contact with condensates in heat exchangers, in sea… In addition, aluminum alloy surfaces can easily appear shiny and develop colorless or white-looking corrosion products. This is an advantage compared to steels, the tarnishing of the surface of which can quickly reveal highly colored products, which are often unsightly.
However, pure aluminum and very low alloy alloys (> 99 wt. %) have very poor mechanical properties compared to low alloy steels. The use of alloys is therefore necessary for many applications. Few metals are soluble in aluminum, and the addition of alloying elements inevitably leads to the formation of multiple intermetallic (IM) phases . The improvement of the processes by various heat treatments and the search for new phases are at the origin of new light alloys with high mechanical properties making it possible to reach very high mechanical resistances. Nevertheless, the presence of intermetallic phases decreases, sometimes quite considerably, the corrosion resistance of the aluminum material. Aluminum alloys therefore have a very varied and very variable behavior in corrosion.
In this article, we will begin by detailing the corrosion properties of pure aluminium: the thermodynamic and kinetic aspects and the main corrosion products. The different aspects of the electrochemical corrosion behavior of aluminum alloys will be discussed, followed by the description of the different corrosion mechanisms of the alloys and the morphologies obtained. Finally, the methods of characterization and measurement of corrosion will be discussed in order to guide the choice of the aluminum material.
