Electrochemical passivation behavior and surface chemistry of 316 L stainless steel coatings on NV E690 steel fabricated by underwater laser direct metal deposition.

The underwater direct metal deposition (UDMD) was employed to deposit 316 L stainless steel (SS316L) coatings on NV E690 steel. The chemical composition gradient from monolayer to trilayer SS316L induces an in-situ phase transformation, thereby enhancing the corrosion resistance. The steady-state passive film grew linearly with the applied potential and exhibited a bilayer structure: a high resistivity barrier layer and a low resistivity outer layer. The growth kinetics of the UDMD fabricated SS316L coatings align with the point defect model. Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni. [Display omitted] • Corrosion resistance was enhanced by coating SS316L through the UDMD technique. • Quantitatively studied the electrochemical and physical properties evolution of the passive film. • The passive film consists of a high-resistivity barrier layer and a low-resistivity outer layer. • The growth kinetics of the UDMD fabricated SS316L coating aligns with the point defect model. • Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni. [ABSTRACT FROM AUTHOR]