What Does Slip Dissolution (SCC) Mean?
Slip dissolution refers to the movement of a material's crystalline structure that occurs when stresses act to open a crack and rupture the protective oxide surface film that naturally develops and covers some metals. The freshly exposed bare metal then dissolves rapidly, resulting in crack propagation. Slip dissolution initiated stress corrosion cracking (SCC) results from local corrosion at emerging slip planes and occurs primarily in low stacking fault materials. Slip dissolution can lead to further cracking and material failure.
A slip dissolution may also be known as a film rupture.
Corrosionpedia Explains Slip Dissolution (SCC)
Slip dissolution is frequently referred to as the film rupture mechanism. It assumes that the stress acts to open the crack and rupture the protective oxide layer on the metal's surface. The slip dissolution mechanism is essential for stress corrosion cracking to initiate and propagate. The process of crack initiation and propagation by the slip dissolution process is very similar.
The slip dissolution theory is based on two postulates:
- The first one postulates that localized plastic deformation at the crack tip ruptures the passivating film, exposing the bare metal at the crack tip. Then the freshly exposed bare metal dissolves rapidly, resulting in crack extension.
- The second one postulates that once the propagation starts, the crack tip remains bare because the film rupture rate at the crack tip is greater than the rate of repassivation. In general, if the repassivation is too fast, dissolution cannot happen that much. However, if the repassivation rate too slow, chemical blunting of the crack is expected to occur.
The dissolution mechanisms' problems are mainly related to transgranular stress corrosion cracking (SCC), where fracture surfaces are crystallographically oriented and flat, matching precisely on the opposite of the fracture surfaces and indicating very little dissolution during the crack growth.