Innovative Stainless Steel Applications in transport ... - Euro Inox

Stress corrosion cracking (SCC)
Stress corrosion cracking occurs only in certain specific alloy/environment/stress
combinations. The environments that most often cause stress corrosion cracking in
stainless steels are aqueous solutions containing chlorides. The required tensile stresses
can originate from applied loads in service or can be residual stresses from fabrication
processes, such as cold working, bending or welding.
Typically, stress corrosion cracking of austenitic stainless steels occurs in chloridecontaining
environments, in the presence of tensile stresses, when the operating
temperature exceeds about 60 °C. SCC is rare in atmospheric applications at ambient
temperatures, although cracking failures have been reported in grades EN 1.4301 and
1.4401 in ceiling structures of indoor swimming pools, in the presence of chloride
deposits from moist air at moderate temperature (Oldfield & Todd 1991, Arnold et al.
1999). Furthermore, there are cases where cold worked EN 1.4301 and 1.4401 have
cracked in marine atmospheres when used in rigging, chain links, deck fittings and
chain plates (ASSDA 1996 and 2008) and, recently, in the field of transportation in the
presence of calcium chloride (CaCl2) and magnesium chloride (MgCl2). The latter are
sometimes used as de-icing salts and dust-control agents. From a practical point of
view, it is important to note that in the case of de-icing salts no SCC was observed
within 2,500 hours at 5 °C, indicating the existence of a material-dependent critical SCC
temperature below which no cracking occurs (Ohligschläger et al. 2005).
Ferritic grades are considered to be virtually immune to this type of attack and duplex
grades are highly resistant. Cracking may also occur in high-strength stainless steels
such as martensitic or precipitation hardening grades. In this case, cracking is almost
always due to hydrogen embrittlement, where susceptibility increases as the strength of
the steel increases.
2.4.2 De-icing and dust-control chemicals
The most common de-icing chemical is sodium chloride (NaCl). Another commonly
used de-icing chemical is calcium chloride (CaCl2). Magnesium chloride (MgCl2) is
also used, but to a lesser extent. Sodium chloride and calcium chloride have proved the
most satisfactory de-icing chemicals, being both cost-effective and readily available.
Their major disadvantage is that they are corrosive to various metals. Adding corrosion
inhibitors to the salt mixtures can reduce their corrosiveness. As salts, they can also
cause salting of ground waters and aquifers, which has been considered a serious
problem (Hellstén & Nystén 2001, Johnson 2004).
As well as being used for de-icing, hygroscopic salts such as CaCl2 and MgCl2 are also
used in summer as dust-suppressant chemicals. In recent years, there have been efforts
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