Resistance to Forms of Corrosion

The resistance of steels to corrosion varies greatly with alloying content playing a major role. Carbon and low alloy steels have the second highest uniform corrosion rates of any metals, while high alloyed stainless steels are generally only susceptible to localized corrosion. The following sections highlight the susceptibilities of steels to forms of corrosion.

Uniform Corrosion

Carbon and low alloy steels are susceptible to uniform atmospheric corrosion while stainless steels are considered resistant. Figure 32 summarizes data collected on various carbon and low alloy steels tested for uniform corrosion in a natural atmospheric environment. The graphs clearly show the decline in corrosion rate over time, with the exception of the severe marine environment.

Stress Corrosion Cracking

Stress corrosion cracking of steels is largely a combination of their strength and environmental susceptibility. High strength steels are susceptible to SCC in corrosive environments. Failures of stainless steels in marine atmospheres have often been a result of SCC. Table 26, Table 27, and Table 28 categorize the SCC susceptibilities of steels in marine atmospheric environments.

Hydrogen Damage in Steels

There are several different mechanisms of hydrogen attack as discussed in Section 2.9.3. Steels are susceptible to all except metal hydride formation. High strength steels are the most susceptible, although even ductile steels have been known to suffer from hydrogen damage.