fig1

Figure 1. Environment-related failure statistics and typical cases of duplex stainless steel from 2000 to 2022. (A) Causes of failures and their proportions and (B) Failure caused by pitting corrosion (Reproduced with permission^[5]. Copyright 2009, Elsevier). (B₁) Pitting corrosion was observed at the weld during the industrial inspection, (B₂) cross-sectional morphology of pitting corrosion, and (B₃) enlarged morphology of a pitted area. (C) Failure caused by crevice corrosion^[6]. (Open access). (C₁) The failure point was located at the joint and (C₂) corrosion occurred along the contact area between the workpieces. A schematic diagram of the crevice corrosion mechanism is shown on the top right. (D) A failure caused by selective corrosion. (Reproduced with permission^[3]. Copyright 2015, Elsevier). (D₁ and D₂) Corrosion caused perforation, and (D₃) the austenite phase was selectively corroded. (E) Failure caused by microbially-induced corrosion (MIC). (Reproduced with permission^[7]. Copyright 2014, Elsevier). (E₁) Corrosion caused perforation at the weld, (E₂) the internal tube was covered with corrosion products, (E₃) biofilm was observed in the corrosion products, and (E₄) corrosion products containing sulfur element (S), indicating that corrosion was caused by sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB). (F) Failure caused by sulfide stress cracking^[8]. (Open access). (F₁) Cracking occurred near the weld/matrix interface, (F₂) cracks propagated along the side of the fusion line, and (F₃) fracture exhibited typical cleavage features. (G) Failure due to stress corrosion cracking. (Reproduced with permission^[4]. Copyright 2018, Elsevier). (G₁) Cracks were visible along the length of the pipe and there was significant pitting corrosion on the pipe surface, (G₂) cross-sectional cracks with obvious dendritic bifurcations, (G₃) at the crack-propagating regions, the cracks propagated within both ferrite and austenite and (G₄) at crack-tip regions, the cracks expanded preferentially in ferrite.