The effect of surface modification on the corrosion protection ability of the passive films of sensitized UNS S31803 duplex stainless steel

ABSTRACT

The influence of sensitisation heat treatment, surface roughness and repetitive cyclic voltammetry (RCV) procedure (that was used to create passive films on the surface of sensitised samples) on the corrosion behaviour of UNS S31803 duplex stainless steel was evaluated using sodium hydroxide etching, double-loop electrochemical potentiodynamic reactivation (DLEPR), potentiodynamic polarisation, Mott–Schottky analysis, X-ray diffraction and optical microscopy techniques. The results showed that prolonged sensitisation time leads to the formation of defective passive films on the surface. In addition, as the substrate surface roughness decreases, the defect concentration in the resulting passive film decreases. Moreover, thick passive films that were created at a high number of RCV cycles contain fewer defects than the thin ones. Finally, the specimens with smooth surfaces, thick passive films and low degree of sensitisation exhibit high corrosion resistance due to their intact passive layers formed on their surfaces.

GRAPHICAL ABSTRACT

KEYWORDS:

• UNS S31803 duplex stainless steel
• sensitisation heat treatment
• Mott–Schottky analysis
• repetitive cyclic passivation
• roughness

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Khashayar Morshed-Behbahani http://orcid.org/0000-0002-1577-6552

Pooria Najafisayar http://orcid.org/0000-0002-0725-7760

Mahmoud Pakshir http://orcid.org/0000-0002-8627-0460

Nika Zakerin http://orcid.org/0000-0002-0093-0828