Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
Steel structures are primarily composed of steel components, characterized by steel beams, steel plates, steel columns, steel trusses, and other elements; they are a major type of building structure, connected through welding, bolts, or rivets between each member or component.
When damage occurs in a steel structure, it should be identified and addressed immediately.
(1) Insufficient load-bearing capacity due to changes in load or revisions to standards and regulations;
(2) Deformation, distortion, loss of functionality, or indentation of components caused by various accidents, leading to weakened cross-sections, warped members, or cracked connections;
(3) Deformation, cracking, or warping of components or connections caused by temperature differences;
(4) Corrosion and electrochemical corrosion caused by chemical erosion, weakening the cross-section of steel structure components;
(5) Other issues including errors in design, production, or construction, as well as illegal use or operation during the service period.
First, the causes of stress corrosion cracking formation:
(1) Stress corrosion with activated pathways
When the cathode is large and the anode is small, the dissolution of the anode manifests as localized corrosion damage. As long as the anode remains at the crack tip during the corrosion process, the crack remains in an activated state without passivation, while other areas (both sides of the crack opening) passivate, allowing the crack to propagate forward until fracture.
(2) Stress corrosion with strain-induced active pathways
Under stress, the passivation film breaks, exposing the metal at the crack site, which becomes an active anode and dissolves. During the corrosion process, the breakage of the passivation film occurs simultaneously with the passivation of the broken film. Under continuous strain conditions, the passivation film is again destroyed, allowing corrosion to continue.
(3) Hydrogen embrittlement stress corrosion
The corrosion cell consists of a small cathode and a large anode. The large anode dissolves, resulting in uniform corrosion. If hydrogen evolution occurs in the smaller cathode region, it leads to localized hydrogen evolution in the cathode region, causing brittle fracture under continuous loading, and stress corrosion progresses smoothly. As cracks form, stress and strain concentration at the cracks promote hydrogen accumulation in the metal toward the cracks, leading to stress corrosion cracking.
The formation of stress corrosion requires the combined action of three factors: material, medium, and tensile stress. Therefore, measures must be taken from all three aspects of influencing factors, from product structural design, installation and construction to production management.
(1) Material: Duplex stainless steel material; select welding materials with the same chemical composition and structure as the base material (equal composition principle);
(2) Medium: The possibility of corrosion of the base metal by the medium must be specifically considered. To reduce stress corrosion in specific environments, corrosion inhibitors can be added to the medium. Through surface treatment technology, sacrificial anode coatings or physical isolation coatings can also be prepared on the component surface.
(3) Stress includes:
Selecting reasonable joint forms during welding to reduce residual stress;
Ensuring correct welding sequence;
Appropriate heat input;
Reducing stress after welding.
