Measures to Prevent Stress Corrosion Cracking (SCC)
Stress corrosion cracking (SCC) can lead to catastrophic material failures if not properly managed. To mitigate this issue, the following measures are commonly implemented:
1.Selecting Appropriate Materials
The choice of materials plays a critical role in preventing SCC. Materials should be selected based on the stress and operating conditions of the components. For example:
Copper alloys should be avoided in environments containing ammonia due to their high sensitivity to SCC.
In high-concentration chloride environments, materials like low-carbon, high-chromium ferritic stainless steel, high-silicon chromium-nickel stainless steel, or nickel-based and iron-nickel-based corrosion-resistant alloys are recommended.
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2.Reducing or Eliminating Residual Tensile Stress
Residual tensile stress is a significant factor contributing to SCC. To address this:
Designs should minimize stress concentrations.
Heating and cooling processes must be uniform, and annealing can be employed to relieve internal stresses.
Surface treatments like shot peening or surface heat treatment can induce residual compressive stress on the surface layer of components, effectively reducing SCC risks.
3.Improving Environmental Conditions
Two approaches can help mitigate SCC by altering the surrounding medium:
Reduce or eliminate harmful ions that promote SCC. For instance, purifying water to lower chloride ion concentrations can significantly reduce chloride-induced cracking in austenitic stainless steel.
Add corrosion inhibitors to the environment. For example, adding
300×10−6mol/L of phosphate to high-temperature water greatly enhances the SCC resistance of chromium-nickel austenitic stainless steel.
Applying Electrochemical Protection
Metals are prone to SCC only within specific electrode potential ranges in a medium. Electrochemical protection methods can shift the metal’s potential away from these sensitive regions. Common methods include:
Cathodic Protection: This technique is widely used but is unsuitable for high-strength steel or materials sensitive to hydrogen embrittlement.
Sacrificial Anode Method: In some cases, sacrificial anodes are employed for effective electrochemical protection.
By combining these measures, SCC can be effectively managed, ensuring the long-term reliability and safety of critical components in corrosive environments.