Used Alloys and their Properties

The composition of alloying elements of mild steel is commonly 0.02 to 0.03 percent sulfur, 0.03 to 0.08 percent phosphorus, 0.4 to 0.5 percent manganese, and 0.1 to 0.2 percent carbon. 

The last two digits identify the aluminum alloy or indicate the alloy purity. In the alloys of the Ixxx series, the last two digits 

Name Major Alloying Element Name Major Alloying Element 

The 2xxx (aluminum-copper) alloy series started to be used frequently with the development of 24S (2024) in 1933 for maximum solubility of alloying elements in the solid phase. Due to their high strength, toughness and fatigue resistance, modifications of 24S are widely used today for aircraft applications. However, the alloys of these series, in which the copper is major alloying element, are less corrosion-resistant than the alloys of other series. Copper increases the efficiency of the cathodic counter reaction of the corrosion, such as O2 and H+, reduction reaction and, thus, the presence of copper increases the corrosion rate.  

Despite its inferior corrosion resistant properties, A1 2024 is substantially used due to the fact that it is a p eculiar alloy used in the fuselage structures of aircrafts, where the corrosion resistance properties are compromised for the sake of mechanical strength also due to the characteristics of its potential environmentally friendly binders, for instance sol-gel coating. 

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