Aluminum Alloys
Aluminum Alloys.
Aluminum alloys are used primarily because of their low weight, the
ease with which they can be formed and fabricated, and their corrosion
resistance in many atmospheric and immersion environments. They are not,
however, resistant to corrosion in many marine environments and are subject to
crevice corrosion, pitting, and in some alloys, stress corrosion cracking. The
alloys are also very subject to galvanic corrosion as they have an anodic
potential with respect to most other metals (ref Galvanic Corrosion Chart or Galvanic Corrosion Table and Galvanic Series Metals Seawater).
1000 Series Aluminum Alloys.
This series of alloys are essentially unalloyed aluminum. While they
have fairly good corrosion resistance as compared to other aluminum alloys, they
have relatively low strength. They are subject to crevice corrosion and pitting.
2000 Series Aluminum Alloys.
This series of alloys are alloys of aluminum and copper. These alloys
are relatively high in strength and are widely used in the aerospace industry.
The corrosion resistance of these alloys is inferior to most other aluminum
alloys.
3000 Series Aluminum Alloys.
This series of alloys are alloys of aluminum and manganese. Their
corrosion performance is roughly comparable to the 1000 series alloys.
5000 Series Aluminum Alloys.
This series of alloys are alloys of aluminum and magnesium. The are
relatively low in strength and cannot be heat treated to obtain higher
strengths. Their corrosion performance in most environments is superior to other
aluminum alloys with the exception of the 1000 series. They are, however,,
subject to both pitting and crevice corrosion, particularly in marine
applications.
6000 Series Aluminum Alloys.
This series of alloys are alloys of aluminum, magnesium, and silicon.
They are relatively high in strength and can be heat treated to obtain higher
strengths. Their corrosion performance in most environments is somewhat inferior
to the 5000 series alloys but is acceptable in many applications. They are
subject to both pitting and crevice corrosion.
7000 Series Aluminum Alloys.
This series of alloys are alloys of aluminium and zinc. They are heat
treatable to obtain high strengths. Their corrosion performance in chloride
containing environments application is inferior to other aluminium alloys. If
they are used, care must be used to control crevice and pitting corrosion attack unless
the effects of these forms of attack are not functionally significant. Some of
the 7000 series alloys are subject to stress corrosion cracking when heat
treated to high strength levels.
Cast Aluminium Alloys.
Of the cast aluminium alloys, alloy A-356 has the best overall balance
between mechanical properties, castability, and corrosion resistance and is the
most commonly used aluminium casting alloy for corrosion service. Its corrosion
performance is comparable to the 6000 series wrought alloys.
see also:
Aluminum Atmospheric Corrosion
Aluminium Pitting Crevice Corrosion
Aluminium Stress Corrosion Cracking
Alluminium Properties and Corrosion Resistance
ALUSelect: a computer-based reference database containing technical information on the most widely used aluminium alloys. This freely accessible web-site allows the user to obtain information about the mechanical, physical and chemical properties of aluminium alloys. At present, 35 wrought alloys and 12 casting alloys are indexed.
AluMatter: aluMATTER is a freely-accessible, award-winning website that provides innovative and interactive e-learning resources for aluminium science and technology.
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