What is the corrosion mechanism of irradiation lines on metals?
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Combined with the various characteristics of metal corrosion caused by irradiation lines discussed previously, its core mechanism of action can be divided into the following categories:: Microscopic defect induction mechanism High-energy irradiation generates a large number of microscopic defects such as dislocation rings, vacancies, and helium bubbles inside the metal, providing a fast channel for ion diffusion in the corrosion medium, while increasing the atomic migration rate and accelerating the matrix corrosion process. Grain boundary element segregation mechanism Irradiation will drive the redistribution of corrosion-resistant elements such as Cr and Ni at metal grain boundaries, resulting in the segregation phenomenon of poor chromium and rich nickel, destroying the dense passivation film on the surface of stainless steel and other materials, and greatly increasing the susceptibility to intergranular corrosion. Ionizing radiation will change the kinetic balance of the electrode reaction. Through the semiconductor effect of radiation electrochemistry, it can not only accelerate the electrochemical corrosion process of the metal couple, but also inhibit local pitting corrosion under certain conditions. Radiation-corrosion synergy mechanism Radiation hardening and local strain concentration induced by radiation will form a coupling effect with the corrosive environment, further inducing radiation-induced stress corrosion cracking (IASCC) under stress synergy, accelerating the initiation and propagation of cracks. Special self-healing reverse mechanism In some nickel-based alloys, interstitial atoms generated by low-dose irradiation can fill grain boundary vacancies, block the penetration channels of corrosive media, and form a self-healing effect, which in turn inhibits corrosion to a certain extent.
The poster summarized it very well. These three mechanisms are indeed the core paths through which radiation affects corrosion. I'll add something: In actual engineering, these mechanisms often do not act alone, but are coupled with each other. For example, microscopic defects will aggravate grain boundary segregation, and segregation will change the local electrochemical environment. It is recommended that interested friends check the stress corrosion cracking cases of 316 stainless steel under neutron irradiation. Many studies have mentioned that the chromium depletion zone induced by irradiation will significantly reduce the stability of the passivation film. In addition, the corrosion rate varies greatly under different irradiation dose rates. This parameter should be paid attention to when doing experimental simulations. If you want to go deeper, you can read some reviews in the field of nuclear materials, such as relevant documents in the Journal of Nuclear Materials. Of course, when it comes to a specific material system, it is best to draw conclusions based on experimental data.