Stress Corrosion Cracking and Hydrogen Embrittlement
Stress corrosion cracking (SCC) and hydrogen embrittlement are two of the most significant forms of corrosion failure in many industrial and natural settings. Both involve the application of an external force, typically in the form of mechanical stress or electrical potential, as a contributing factor in corrosion initiation and growth. While each form of damage is powerfully destructive in its own right, the combined effects of both can be even more catastrophic and dangerous.
Stress corrosion cracking is defined as the brittle rupture of a material due to the combined action of corrosion and tensile stress. This type of corrosion damage is typically associated with oxides and chlorides that either form a passive barrier or strongly adsorb to the surface of the damaged material. In addition, a high concentration of dissolved oxygen and an elevated level of mechanical stress can also lead to increased susceptibility to stress corrosion cracking.
The basic mechanism of stress corrosion cracking involves the formation of a crack at a stress concentration point due to the combined action of tensile stress and corrosion in the affected material. This crack generally propagates very slowly, and is highly dependent upon the material properties and environmental factors that determine the rate at which the material corrodes. In general, material surfaces that are exposed to an aggressive and/or oxidizing environment will experience higher rates of corrosion, and in turn, a higher likelihood of stress corrosion cracking.
Hydrogen embrittlement is another form of corrosion-related damage that occurs due to the diffusion of hydrogen into the affected material. Hydrogen embrittlement is often caused by exposure to electrolytic solutions or the burning of hydrogen-bearing fuels, and can lead to catastrophic failure of a material if the chemical environment is not properly controlled and monitored. This type of corrosion is characterized by the presence of a large number of tiny cracks in the affected region. These cracks are generally evenly distributed throughout the material and, as a result, can cause catastrophic failure at a much lower stress concentration than in stress corrosion cracking.
By understanding the basic mechanisms of both stress corrosion cracking and hydrogen embrittlement, it is possible to take steps to prevent or at least minimize the occurrence of these devastating forms of corrosion. In general, materials that are exposed to corrosive environments should be protected with an appropriate coating system. This will not only reduce the likelihood of corrosion damage, but also increase resistance to stress corrosion cracking and hydrogen embrittlement. In addition, periodic monitoring of industrial systems to identify areas of high pain concentration should also be conducted to ensure that no cracks are present. Finally, it is essential to ensure that the chemical environment of any corroding material is properly controlled and monitored, as this can greatly reduce the risk of catastrophic failure. By observing these simple best practices, the potential for corrosion-related damage can be greatly reduced, and the safety and security that come with it can be greatly increased.
