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The effect of tellurium (Te) on the localised corrosion mechanism in 15–5PH stainless steel is studied in a simulated marine environment. The addition of Te changed the composition and size of the inclusions, which significantly affected the localised corrosion mechanism of the steel. Scanning Kelvin probe force microscopy and current-sensing atomic-force microscopy results show that the inclusions have good electrical conductivity and are always electrochemically dissolved. During the corrosion process, MnS acted as the anodic phase and was preferentially dissolved. The portion of Te in Te-containing complex inclusions increased the Volta potential of the inclusions and changed the localised corrosion mechanism. The appropriate addition of Te increased the pitting potential of 15–5PH stainless steel, thereby improving its localised corrosion resistance. However, superfluous addition of Te resulted in corrosion-resistance attenuation. This can be attributed to the continuous cathodic effect of the larger Te portion in the complex inclusion. The dissolution of Te oxides destabilised the passivation film. • The addition of Te to stainless steel changes the localised corrosion mechanism. • Galvanic coupling effects between the MnS-Te inclusion and steel matrix were revealed. • Appropriate Te addition enhanced the pitting potential and corrosion resistance of 15–5PH stainless steel. • Superfluous Te addition attenuated the corrosion resistance of 15–5PH stainless steel. [ABSTRACT FROM AUTHOR]

Irradiation-assisted stress corrosion cracking normally initiates and propagates along grain/phase boundaries. Here, by using scanning Kelvin probe force microscopy, we characterized the Volta potential difference (VPD) changes prior and after proton irradiation at austenite/carbide (γ/C), ferrite/carbide (δ/C) and austenite/ferrite (γ/δ) interfaces in a 308 L stainless steel. It was found that, prior to irradiation, γ/C boundary had the lowest VPD, followed by δ/C and γ/δ. VPDs of all three types of phase boundaries slightly decreased after proton irradiation, wherein the γ/C boundary showed the largest VPD drop, followed by δ/C and γ/δ. The γ/C interface demonstrates the highest tendency of corrosion. [Display omitted] • The role of carbides at phase boundaries on IASCC is evaluated. • Irradiation promotes corrosion at γ/C, δ/C and δ/γ interfaces. • The γ/C interface shows the lowest Volta potential and even more so upon irradiation. • The Cr content seems to dominate the corrosion tendency evolution at all types of interfaces. [ABSTRACT FROM AUTHOR]

The degradation of passive films of a stainless steel by S. algae was investigated at the single-cell level. The focused ion beam-scanning/transmission electron microscopy showed that the passive film underneath the adherent S. algae cell was significantly thinner than that without bacterial coverage after 3 days of inoculation. Atomic force microscopy (AFM) in the nano manipulation mode was used to move the bacterial cell and AFM in the dynamic mode revealed the nanoscale corrosion pit underneath. Peak force tapping-frequency modulation mode of AFM showed high Volta potentials at the pit center and low Volta potentials around the bacterial cell. • FIB-SEM/TEM and multimode AFM are used to study MIC at the single-cell level. • FIB-SEM/TEM shows degradation of stainless steel passive film by a S. algae cell. • Multimode AFM is used to investigate pitting corrosion underneath a S. algae cell. [ABSTRACT FROM AUTHOR]

• TIG Welding causes significant changes in morphology and chemical composition of the phases in the heat affected zone (HAZ). • Thermo-mechanical simulation was used to study the effects of the thermal parameter on the microstructure evolution in the HAZ. • Electrochemical polarization showed the different passivation behaviour of the phases in the HAZ. • Surface potential surveys revealed the reduction in internal galvanic activity in the duplex HAZ. A Gleeble-simulated microstructure of the heat-affected zone (HAZ) of tungsten inert gas (TIG) welded grade 2205 duplex stainless steel (DSS) has been produced. Local changes in microstructure chemistry were correlated to galvanic activity using scanning Kelvin probe force microscopy (SKPFM) and electro-chemical polarization. The simulated HAZ had a marked reduction of SKPFM measured Volta potentials. This was reflected in a clear reduction of the electrochemical potential difference of the activation peak between the ferrite and austenite phase. The implications of these observations are discussed for reducing the likelihood of environmentally assisted cracking. [ABSTRACT FROM AUTHOR]