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Nickel‐free high‐nitrogen‐alloyed stainless steels like the P2000 (X13CrMnMoN18‐14‐3) were developed to enhance the strength and corrosion resistance of austenitic stainless steels like 304 and 316 while keeping the typical high ductility. The mechanical and corrosive properties of P2000 were investigated and compared with 304 and 316 to highlight the application opportunities of this new alloy. The microstructure of the solution‐annealed condition was characterised by electron backscatter diffraction and the mechanical properties were studied by uniaxial tensile tests, Charpy impact tests and hardness measurements. The passivation behaviour was analysed using the electrochemical potentiodynamic reactivation, whereas the pitting corrosion resistance was compared by pitting potentials and pitting temperatures. However, secondary thermal influences or suboptimal heat treatment can impair the corrosion resistance due to the precipitation of secondary phases and the resulting sensitisation. Thermodynamic calculations and artificial ageing treatment in the range of 500–900°C for up to 100 h were used to determine critical time–temperature parameters for sensitisation. The microstructure of the various aged states was evaluated by scanning electron microscopy and compared with the degrading corrosion resistance characterised by the KorroPad method.

Microbiologically influenced corrosion induced by bacteria has been studied for many years. Corrosion is known to be sensitive to the presence of microalgae, such as Phaeodactylum tricornutum. However, the life activity of P. tricornutum that influences the general and localized corrosion of carbon steel is not fully understood. The current study uses a combination of immersion tests and electrochemical experiments with a detailed surface characterization to reveal the naturally formed corrosion products with/without the presence of P. tricornutum. The results show that samples suffer from pitting corrosion and the averaged pit depths are approximately 15 μm under a light–dark cycle condition or a 24‐h constant light condition. Meanwhile, the corrosion products are mainly comprised of γ‐FeOOH and Fe3O4 in a constant light condition. However, γ‐FeOOH, Fe3O4, and FeCO3 are found in a light–dark cycle. This study proposes the fundamental mechanisms of the effect of P. tricornutum life activities on the corrosion performance of Q235 carbon steel, to fulfill the knowledge gaps of the presence of microalgae inducing the general and pitting corrosion of carbon steel.

In this study, the local electrochemical activity of untreated and passivated (natural or chemical passivation) zinc specimens was observed during immersion in a 0.1-M NaCl solution. The localized anodic activity during the exposure, measured with the scanning vibrating electrode technique, was linked to zinc dissolution by the pitting corrosion mechanism. It was correlated to specific corrosion products characterized by Fourier transmission infrared (FTIR) microscopy. FTIR molecule maps were produced from individual pitting corrosion sites (100–200 µm in width). With argon ion beam milling and latest energy-dispersive X-ray spectroscopy (EDS) technology, element maps with a high spatial resolution (≪100 nm) were recorded from abrasion- and beam-sensitive corrosion products, showing a residual layer structure. This study demonstrates the capability of FTIR mapping, cross-section polishing, and state-of-the-art scanning electron microscopy imaging, and EDS element mapping to produce high-resolution elemental, molecular, and visual information about pitting corrosion mechanisms on a hot-dip galvanized steel sample. acceptedVersion

Pitting corrosion and crevice corrosion of passivated steels were measured by using a double-mode syringe electrolyte cell built on an environment chamber. The setup, when set in noncontact mode, could measure pitting potentials and critical temperatures, and crevice corrosion potentials if in contact mode. It could be employed to distinguish the pitting and crevice corrosion damage of reinforcing steel in concrete.

Al-alloy, AA5083, as lightweight structural material with favourable mechanical properties and, compared to other lightweight materials, good corrosion resistance has an increasing usage in marine environment. It is well known that all Al-alloys, including AA5083, in presence of chloride ions are more prone to corrosion. Determination of corrosion behaviour of AA5083 in seawater and brackish water has been investigated and compared at 18°C, 25°C and at 30°C. In order to obtain more accurate and realistic results, fresh seawater and brackish water were sampled as an electrolyte in Sibenik region. The investigation was carried out using following electrochemical methods: open circuit potential measurement, electrochemical impedance spectroscopy, linear polarization resistance, potentiodynamic polarization and cyclic polarization. After potentiodynamic polarization measurement, each alloy was exterminated using metallographic microscope in order to clarify corrosion morphology. Obtained results have shown that increase in temperature leads to an increase in corrosion activity of AA5083 in both electrolytes, while microscopic examination reveals that dominate type of corrosion is pitting.

Microbially influenced corrosion (MIC) on internal pipeline surfaces has become a severe problem during the water injection process in secondary oil recovery. The formation of a biofilm, normally dominated by sulfate-reducing bacteria (SRB), is believed to be the critical step of the MIC process. A continuously fed biofilm simulating the water injection process was operated to investigate the influence of biofilm development on MIC behavior in the early phase of corrosion development. The development of the corrosion product film and biofilm was monitored for 5 months with electrochemical impedance spectroscopy, linear polarization resistance, scanning electron microscopy, 3D optical profiling, and direct weight measurement. MIC development was found to comprise three phases: initialization, transition, and stabilization. The initialization phase involved the formation of the corrosion product layer and the initial attachment of the sessile microbes on metal surface. In the transition phase, the MIC process gradually shifted from charge-transfer-controlled reaction to diffusion-controlled reaction. The stabilization phase featured mature and compact biofilm on the metal surface, and the general corrosion rate (CR) decreased due to the diffusional effect, while the pitting CR was enhanced at a lower carbon source level, which supported the mechanism of direct electron uptake from the metal surface by SRB.

Spin-on-glass deposition was investigated as viable alternative to increase the durability and performance of 316L steel in chloride environment. The buildup of a detrimental interface oxide was prevented by non-oxidative thermal curing of the coatings, which leads to a transformation to an inorganic, SiO2-like material. The degree of polymerization was found dependent on the curing temperature; however, even curing at the maximum investigated curing temperature of 800 °C led to still incomplete transformation, showing less SiO2-like character with respect to thermally grown oxide or fused silica. Electrochemical analysis by cyclic polarization indicated that the coatings behave as imperfect barrier coatings, which may enhance the passive properties of the substrates; however, there is still some statistical scatter in the quality of the coatings. While there is a tendency for an increase of the upper limit of the breakdown potential, there is also a decrease of the lower limit. It was found that such lower quality coatings showed, in association with substrate defects, unevenly distributed coating flaws, which may act as initiation points of pitting corrosion and decrease the corrosion resistance of coated substrates. Further, the films showed instability in aqueous environment due to imperfect polymerization.

The microstructural characterization and pitting corrosion behavior of Z3CN20.09M duplex stainless steel were investigated by TEM, potentiodynamic polarization, and electrochemical impedance spectroscopy after thermal aging at 475 °C for 0, 500, 1000, 2000, and 3000 h. The results showed that the ferrite in the steel decomposes into coherent Cr-rich, Fe-rich, and G phases. No any precipitates were found in the austenite during the thermal aging process. It is revealed that the pitting resistance of this steel has a negative relationship with increasing aging time and the priority nucleation position changes before and after the thermal aging process. The composition fluctuation region adjacent to the G phase and the Cr-depleted region around the Cr-rich phase are preferential to form pits. Therefore the G phase precipitation and the formation of Cr-depleted region are harmful to the pitting resistance of the steel.

It is possible to determine the pitting corrosion resistance of a stainless steel in a given solution of a chemical process by electrochemical techniques. However, it is known that the result is influenced by the test parameters. The aim of this study was to determine the influence of the main test parameters, scan rate, imax; agitation/flow rate, and surface pretreatment on the electrochemical response of 316Ti/1.4571 stainless steel in an acidic (250 ppm Cl−, pH: 4, T: 30 °C) and an alkaline (4% Cl−, pH: 9, T: 80 °C) solution. The results were compared with classical immersion test results. The main result was that the agitation/flow rate had the greatest impact, with stagnant conditions giving very conservative results, followed by imax, which had an influence on the repassivation potential.

The susceptibility of stainless steels to pitting corrosion is an essential characteristic of these alloys, since this kind of phenomenon may affect the mechanical integrity of the material and consequently cause unexpected failures. In order to avoid or minimize this localized corrosion process it is possible to enhance the protective capacity of the passive layer from the stainless steels and one of the methods to obtain this result is the chemical passivation treatment. In this context, the effect of the passivation treatment with nitric acid on pitting corrosion resistance of the AISI 410 and 17–4 PH stainless steels in chloride containing media is investigated. For this, two surface conditions are studied for each material: ground and chemically passivated. The corrosion behavior is evaluated by cyclic polarization tests in 0.6 M NaCl and the morphology of pitting corrosion is characterized by optical microscopy. According to the results, the applied surface treatment causes an improvement on the pitting corrosion resistance of both stainless steels, and the greatest increase on pitting potential is obtained to the 17–4 PH stainless steel.

To investigate the role of intermetallic particles in the localised corrosion of AA7075-T6, three particles were monitored over 16 hours immersion in 3.5 wt.% KCl solution. These were examined using Auger electron spectroscopy, energy dispersive x-ray spectroscopy, scanning Kelvin probe force microscopy and focused ion beam-scanning electron microscopy. Despite similar Volta potential measurements, the corrosion microchemistry varied significantly with composition. A Al7Cu2Fe intermetallic resulted in trenching while a (Al,Cu)6(Fe,Cu) intermetallic showed crevice corrosion and sub-surface intergranular corrosion and a Al12Fe3Si intermetallic appeared to be galvanically inactive but showed crevice formation at the matrix interface and sub-surface intergranular corrosion.

Microstructure and pitting corrosion resistance of UNS S32205 DSS weld were systematically studied, and its failure causes were analyzed carefully. The results showed the uneven metallographic microstructures with majority of austenite in the HAZ and then the significantly reduced pitting corrosion resistance of the weld. Furthermore, large potential difference between the both sides of the insulation joint and high salinity of the formation water in the pipeline make the leakage current preferably flow out from the weld and enter the transmission fluid, so localized corrosion happens at the inner surface of the weld and leads to the corrosion perforation eventually.

The corrosion behavior of 3003 aluminum alloy in different media was investigated by electrochemical approaches and immersion tests. It was shown that the corrosion of aluminum alloy was influenced by the composition of the solution. The results indicated that the nitrite ion (NO2−) acted as a corrosion inhibitor. The addition of sulfate ion (SO42−) or nitrate ion (NO3−) can weaken this inhibiting effect. Chloride ion (Cl−) and SO42− can accelerate the corrosion of 3003 aluminum alloy greatly.

The corrosion behaviour of binary Al-Sc alloys (Al-0.3Sc and Al-1Sc, wt%) is investigated in de-aerated 0.6 M NaCl solution, performing potentiodynamic polarisation, potentiostatic transients and electrochemical impedance spectroscopy (EIS) measurements complemented with scanning electron microscopy (SEM). In the presence of chloride ions, both Al-Sc alloys experience localised corrosion (pitting). However, increasing Sc alloying addition leads to an increase of the breakdown potential and the extent of passivation domain, indicating improved resistance to initiation of pitting corrosion. Furthermore, EIS measurements performed at the breakdown state evidenced a higher Rct and a lower depression angle value for the Al-1Sc alloy compared to the Al-0.3Sc one, confirming its better localised corrosion behaviour. Spatial distribution and volume fraction of the Al3Sc secondary phase are microstructural features which play a very important role in determining the corrosion resistance of the Al-1Sc alloy.

Atmospheric corrosion behavior of a commercially pure aluminum AA1035 in rural environment with high Cl− deposition, urban, coastal, and industrial environments was investigated by over 20-year field test in China. AA1035 showed an accelerated corrosion rate in urban environment, a decelerated corrosion rate in industrial environment, and a constant corrosion rate in rural and coastal environment. The corrosion rate of AA1035 in industrial environment was approximately 1.5, 5.0, and 10.0 times as fast as that in coastal, rural, and urban environments, respectively. Moreover, AA1035 in coastal environment (Cl− deposition rate = 45.54 mg · m−2 · d−1) and rural environment (Cl− deposition rate = 25.62 mg · m−2 · d−1) suffered intergranular corrosion, and the maximum depth was about 250 and 50 µm after 20-year exposure, respectively. The higher the deposition rate of Cl− was, the more serious intergranular corrosion AA1035 suffered. In addition, in industrial and urban environments, AA1035 mainly suffered pitting corrosion, and the maximum pit depth was approximately 250 and 10 µm after 20-year exposure, respectively.

This is a study of the effect of repetitive TIG (tungsten inert gas) welding passes, melting and remelting the same material volume on microstructure and corrosion resistance of 2507 (EN 1.4410) su ...