2024 Volume 73 Issue 7 Pages 168-174
In order to elucidate the grooving corrosion suppression mechanism of Cu and Ti added ERW steel pipes, welded portions were immersed in salt water after polishing without using the SPEED method, which electrolytically polishes the specimen using a non-aqueous electrolyte. Sulfides were observed using FIB processing. Before immersion, MnS and Ti4C2S2 were observed. After immersion, Cu7.2S4 precipitated on the MnS on the immersed surface. Furthermore, Ti4C2S2 did not dissolve. Addition of Ti produced insoluble Ti4C2S2, which reduced the number density of MnS, and addition of Cu precipitated insoluble Cu7.2S4 on MnS, suppressing the dissolution of MnS.
