The corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) performed simultaneously with real-time hydrogen evolution measurements optical imaging the corroding surface. investigation revealed substantial deviations from linearity close proximity potential. In particular, differences slope current/potential curves were observed for small polarizations above or below These...

This work investigates the hydrogen evolution process on magnesium by real time imaging of corroding surface at free corrosion potential and during potentiodynamic polarization in alkaline neutral environments, presence absence chloride ions. High-magnification from side view discloses that three different types bubbles are generated corrosion: i) large stable uncorroded regions, ii) a stream fine front iii) medium size behind front. It is proposed generation streams due to disruption...

Alloy 600 was exposed to H2-steam simulate the oxidation that occurs in high temperature water where this alloy is known be susceptible SCC. Analytical electron microscopy employed characterize early stages of aid developing an understanding stress corrosion cracking behaviour alloy. The oxide consisted sub-surface Cr2O3 particles, preferential intergranular and formation surface Ni nodules. measurements residual stresses at microscopic level using a recently-developed FIB micro-hole...

Warm-forged Type 304L stainless steel specimens have been tested in high temperature hydrogenated water under slow strain rate tensile test conditions to investigate the effect of machining on stress corrosion crack initiation. Roughness, residual and cross-section microstructures as-machined surfaces were characterized prior tests, both plan-view examinations performed post-test. The results indicated that produced a deformation layer by an ultrafine-grained outer highly deformed inner...

The effect of machining on stress corrosion crack initiation annealed Type 316L stainless steel was investigated through accelerated testing in high-temperature hydrogenated water. It observed that cracks only initiated machined surfaces with marks perpendicular to the loading direction and a porous inner oxide layer identified as an important factor contributing initiation. Furthermore, most stopped within machining-induced near-surface ultrafine-grained residual stresses did not appear...

In this work, a model to account for the superfluous hydrogen evolution mechanism during anodic polarization of Al is proposed. The based on assumption that simultaneous presence an current, produced at some distance from corrosion front, and conditions promote local depassivation such as, example, chlorides, induces localized rupture pre-existing oxide/hydroxide film. This leads formation regions where electrolyte either in contact with metal or separated only by poorly protective salt...

In the literature it is a common belief that electropolishing mitigates primary water stress corrosion cracking (PWSCC) because removes superficial cold work. Here, shown electropolished Alloy 600 (UNS N06600) exposed to hydrogenated steam undergoes internal Cr oxidation, whereas mechanical polishing induces external oxidation. This has implications for SCC initiation, which been tested with different surface preparations (electropolishing and polishing) using reverse-U-bend (RUB) C-ring...

Abstract Water reduction, which leads to the evolution of hydrogen, is a key cathodic process for corrosion many metals technological interest such as magnesium, aluminium, and zinc; its understanding critical design new alloys or protective treatments. In this work, real-time hydrogen measurement was coupled with potentiodynamic measurements on high-purity aluminium AA2024-T3 alloy. The results show that both materials exhibit superfluous during anodic polarisation presence cathodically...

When electrochemical techniques are used to probe the surface of corroding magnesium with aim obtaining quantitative information on corrosion process, two peculiarities generally observed: i) anodic polarization, rate hydrogen evolution increases instead decreasing and ii) during impedance spectroscopy measurements, an inductive contribution is often observed at low-frequency end spectra. The presence these phenomena clearly has impact methodology that should be applied correctly estimate...

This present work introduces a new understanding of the precursors events to Stress Corrosion Cracking (SCC) initiation in nuclear power plant components, exploring role grain boundary migration and Preferential Intergranular Oxidation (PIO). In this work, systematic evaluation Alloy 600 exposed low pressure H2-steam over range oxidizing potentials vicinity Ni/NiO transition has revealed notable decrease PIO for conditions more than transition, whilst local diffusion-induced occurs...

Surface machining is often assumed to be detrimental stress corrosion cracking (SCC) in nuclear power plant components because of localized deformation, high associated hardness, roughness and tensile residual stresses. However, the present work, SCC initiation studies for a warm-forged Type 304L stainless steel high-temperature water showed that ~1–2 μm thick ultrafine-grained layer introduced by improved resistance. Removing macroscopic ridges via grinding decreased but led more extensive...

In this work, the effect of corrosion testing methodology on degradation anodized and post-treated AA-2024T3 specimens is considered. Two post-treatments are selected for layers, namely hydrothermal sealing cerium-based post treatment. The two such that in one case protection mainly arises from a barrier (hydrothermal sealing) other it active inhibition (cerium-based treatment). It found salt spray immersion provide similar results hydrothermally sealed oxides, but differ substantially...

The corrosion performance provided by two anodizing treatments aiming at obtaining films with comparable thickness but different pore morphology was evaluated immersion, salt spray, and a hybrid tests. test performed in cycles alternating between immersion spray progression selected times electrochemical impedance spectroscopy (EIS). EIS indicated that, during test, the self-sealing of pores due to precipitation aluminium hydroxide favored, it substantial contribution improved resistance....

In situ analytical transmission electron microscopy (TEM) can provide a unique perspective on dynamic reactions in variety of environments, including liquids and gases. this study, TEM techniques have been applied to examine the localised oxidation that occur Ni-Cr-Fe alloy, Alloy 600, using gas environmental cell at elevated temperatures. The initial stages preferential intergranular oxidation, shown be an important precursor phenomenon for stress corrosion cracking pressurized water...

Fatigue crack growth experiments have been performed on high and low sulphur Type 316 austenitic stainless steel specimens in simulated Pressurised Water Reactor primary coolant environments evaluated via microstructural characterisation techniques to further the understanding of mechanistic behaviour. At relatively loading frequencies, enhanced for both appeared be crystallographic associated with slip localization. However, when frequency was decreased, rates S specimen increased, whereas...

Solution-annealed Alloy 600 samples were tested under active load conditions in a superheated low pressure H2-steam environment over range of oxidising potentials relevant to Primary Water Stress Corrosion Cracking (PWSCC). Increased SCC susceptibility was observed for the more reducing than Ni/NiO transition where deeper Preferential Intergranular Oxidation (PIO) occurred. Advanced microstructural analysis clearly showed that initiated along grain boundaries exhibited Diffusion-Induced...

Cold-worked Type 304L/316L stainless steel specimens, which contained different amounts of martensite (α′/ε), were tested in high-temperature hydrogenated water under slow strain rate tensile (SSRT) test conditions to understand the role on stress corrosion crack (SCC) initiation. These specimens characterized prior and after SSRT tests using complementary analytical techniques. It was observed that a higher necessary induce SCC initiation for cold-rolled 304L compared other cold-worked...