Initiation and propagation of localized corrosion induced by (Zr, Ti, Al)-Ox inclusions in low-alloy steels in marine environment

Local Corrosion Behaviors in the Coarse-Grained Heat-Affected Zone in a Newly Developed Zr–Ti–Al–RE Deoxidized High-Strength Low-Alloy Steel

“…To maintain electrical neutrality, a large amount of Cl - will enter the pitting hole, resulting in the formation of a self-catalytic acidification-occluded corrosion cell ( Figure 12 IIc). Furthermore, some generated cations, such as Ca 2+ , Zr 4+ , Al 3+ and RE 3+ , hydrolyze further, resulting in a drop in the pH value [ 13 , 30 , 32 ], causing a strong acidic environment in the pits and accelerating the dissolution of the composite inclusions ((RE–Zr–Al–Ca)–Ox and Al 2 MgO 4 ) ( Figure 12 IId). TiN inclusion is stable, which is primarily related to its insolubility in strong acids [ 69 ].…”

“…Generally, the types of non-metallic inclusions—such as Al 2 O 3 , MnS, ZrO 2 , CaO and Al 2 MgO 4 —introduced in steels depend on the specific deoxidation techniques [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Inclusions in the steels are often considered as defects that can preferably be attacked by chloride ions in the marine environment, which induce pitting corrosion [ 4 , 16 , 17 ] that has a detrimental impact on application performance [ 18 , 19 , 20 , 21 , 22 , 23 ].…”

“…In addition, oxide metallurgy techniques may lead to the distribution of aggregated inclusions in the matrix, which may cause an effective increase in the active sites of pitting initiation. Thus, to improve the mechanical properties of the CGHAZ, oxide metallurgy technology and rare earth microalloying often result in more complex inclusions, posing challenges in the study of the corrosive behavior of inclusions [ 11 , 13 , 41 , 42 ].…”

Study on the microstructure and corrosion behavior of CoCrNi MEA annealed at different temperatures in Na2CO3/NaHCO3 solution

“…The corrosion rate of the MEA gradually decreases with the increase of annealing temperature, which is coherent with the corrosion As shown in Figure 16a, after the immersion test, the O, Ti, and Al-rich in the A area indicates that A is the oxide, and pitting (B area) occurs around the oxide. This may be attributed to the micro-galvanic corrosion formed between the oxide and the matrix, where the oxide serves as the cathode, and the matrix acts as the anode, [43][44][45] thus, the corrosion of the matrix is facilitated. Consequently, the pitting easily forms around the oxide.…”

Effects of Ti and Cu Addition on Inclusion Modification and Corrosion Behavior in Simulated Coarse-Grained Heat-Affected Zone of Low-Alloy Steels

“…In our previous work, the mechanism of pitting initiation and propagation process induced by (Zr-Ti-Al)-O x inclusions in Zr-Ti deoxidized low-alloy steel were thoroughly investigated [ 28 ]. In previous studies, the impact of Ti and Cu addition on microstructure and toughness in simulated CGHAZ of low-alloy steels [ 15 , 16 ] and the localized corrosion behavior induced by inclusions, such as Al 2 O 3 , MnS, were discussed in detail [ 29 , 30 , 31 ].…”