یکشنبه 16 مهر 1391
Chapter 1 .
Literature Survey of Protection of
Magnesium is one of the light metals. Its density is 1.7 g/cm3 [Aylward and
Findlay, 1974]. This is low compared to other commercial metals. Commonly
used metals like aluminum and steel have densities of 2.7 g/cm3 and 7.9 g/cm3
respectively. Pure magnesium has low strength and is therefore not used for
constructional purposes [Solberg,1996]. Alloyed magnesium on the other hand,
has a high strength-to-weight ratio [Leontis, 1986] compared to other metals. It
is therefore possible to save weight by replacing parts made of steel or
aluminum, by magnesium, without reducing the strength significantly. Of course
changes regarding the design may have to be carried out to compensate for the
lower strength of magnesium [Metals Handbook, 1979] and this may again lead
to an increase in volume. Still, the overall result is a decrease in weight for the
component. Parts that are not exposed to strain like the steering wheel on a car
can be made of magnesium without changing the original design. Other
examples of components that are made of magnesium are cellular phones, laptop
computers and car components like gearbox housings, dashboard mounting
brackets and seat components.
Magnesium has a melting point of 650°C and is the eighth most abundant
element at the earth’s crust [Emley, 1966]. Seawater has a magnesium content of
0.13% which means that one liter of seawater contains 1.3 gram magnesium.
Thus the magnesium industry should never experience a shortage of raw
materials. Other raw materials worth mentioning are magnesite (MgCO3) and