Initial Stages Of Atmospheric Corrosion Research Articles

Modeling research of initial atmospheric corrosion of Q235 carbon steel based on electrical resistance probe

PurposeThis paper aims to discover the mathematical model for Q235 carbon steel corrosion date acquired in the initial stage of atmospheric corrosion using electrical resistance probe.Design/methodology/approachIn this paper, mathematical approaches are used to construct a classification model for atmospheric environmental elements and material corrosion rates.FindingsResults of the experiment show that the corrosion data can be converted into corrosion depth for calculating corrosion rate to obtain corrosion kinetics model and conform corrosion acceleration phase. Combined with corresponding atmospheric environmental elements, a real time grade subdivision model for corrosion rate can be constructed.Originality/valueThese mathematical models constructed by real time corrosion data can be well used to research the characteristics about initial atmospheric corrosion of Q235 carbon steel.

Effect of coastal atmospheric corrosion on fatigue properties of 2024-T4 aluminum alloy structures

To investigate the effect of atmospheric corrosion on the fatigue properties of 2024-T4 aluminum alloy structures during the whole corrosion period, atmospheric and accelerated pre-corrosion fatigue tests were carried out. Field exposure tests were carried out for 7, 12, and 20 years. A laboratory accelerated corrosion test method was proposed to simulate the whole atmospheric corrosion period from initial pitting to the subsequent exfoliation corrosion, and the reliability was verified through an analysis of the corrosion morphology, corrosion products, and thickness variation. Pitting and intergranular corrosion occurred after a short exposure to atmospheric corrosion, and intergranular corrosion was the dominant corrosion damage mode. The fatigue cracks initiated at the deepest boundary of intergranular corrosion. The fatigue life decreased dramatically during the initial stage of atmospheric corrosion and then decreased more slowly. Finally, the mechanism through which atmospheric corrosion affected the fatigue properties was analyzed.

The initial stage of atmospheric corrosion on interstitial free steel investigated by in situ SPM

The initial stage of atmospheric corrosion on interstitial free steel was investigated by ab initio calculation and scanning probe microscopy under different operation modes. Water droplets are adsorbed preferentially on grain boundaries at 95% relative humidity due to their higher surface energy, which is confirmed by ab initio calculation. Atomic force microscopy observation indicates that corrosion preferentially occurs at grain boundaries after immersion under a thin film of NaCl electrolyte, because of the lower relative nobility of grain boundary, which is proved by scanning Kelvin probe force microscope. These results indicate that water adsorption is crucial for initializing atmospheric corrosion.

Initial Stage of Atmospheric Corrosion of NdFeB(M35) in A Simulated Marine Atmosphere

Initial Stage of Atmospheric Corrosion of NdFeB(M35) in A Simulated Marine Atmosphere

The Initial Stages of Atmospheric Corrosion of Iron in a Saline Environment Studied with Time-Resolved In Situ X-Ray Transmission Microscopy

We have investigated atmospheric corrosion of a 50 nm layer of iron covered with a thin layer of NaCl by in situ X-ray transmission spectromicroscopy. We find that upon its deliquescence, a small part of the NaCl layer is rapidly transformed into a sodium oxide (NaOH) species. A large part of the sodium and chlorine ions forms a concentrated solution on the iron surface and becomes segregated, whereby the sodium ions appear stationary and passive during further corrosion progression. In contrast, the chlorine ions appear highly mobile and become concentrated at and travel with the corrosion front, apparently acting as a corrosion catalyst. The corrosion front progression is partly of filiform and partly of radial type. The early iron corrosion products (chloride-containing oxyhydroxides) are short-lived (for some hours) and undergo a transformation as the corrosion front sweeps by from a chlorinated species to a less chlorinated species.

Influence of carbon content and microstructure on corrosion behaviour of low alloy steels in a Cl − containing environment

Corrosion behaviour of low alloy steels (A and B) with different carbon content was studied by a salt fog test and an outdoor test. A commercial weathering steel 09CuPCrNi was used for comparison. The corrosion resistance of steels A and B with homogeneous microstructures was better than that of the commercial weathering steel 09CuPCrNi in the salt fog test. Steel A with an ultra-low-carbon content had far less weathering resistance than the other steels in the outdoor test. Selective corrosion of large pearlite produces stress in initial corrosion product films. Uniform corrosion product films with few cracks tend to form on homogeneous microstructures such as ferrite and bainite, and this is advantageous for the formation of a compact rust layer in the initial stage of atmospheric corrosion. However, uniform microstructures will result in over even interfaces between rust layers and bases, which will lead to frequent peeling of rust layers from bases because stress is induced by large temperature fluctuations and wet-dry alternations. Protection of the rust layer on a low alloy steel is dependent on the rust density and the bonding performance of the rust-base rather than the proportion of the rust phase in the initial stage of atmospheric corrosion. These results indicate that homogenous microstructures, proper amounts of carbon content and fine carbon-rich phases that are produced by appropriate processes are beneficial for the corrosion resistance of steels.

Corrosion Products and Formation Mechanism During Initial Stage of Atmospheric Corrosion of Carbon Steel

The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy (SEM) and Raman spectroscopy. The results showed that two different shapes of corrosion products, that is, ring and chain, were formed in the initial stage of corrosion. MnS clusters were found in the nuclei of corrosion products at the active local corrosion sites. The ring-shaped products were composed of lepidocrocite (γ-FeOOH) and maghemite (γ-Fe 2 O 3) transformed from lepidocrocite. The chain-type products were goethite (α-FeOOH). A formation mechanism of the corrosion products is proposed.

In situ investigations of the interaction of small inorganic acidifying molecules in humidified air with polycrystalline metal surfaces by means of TM‐AFM, IRRAS, and QCM

AbstractInitial atmospheric corrosion of copper, silver, and iron induced by humidity and oxidizing agents was studied in situ by three highly surface‐sensitive and complementary techniques: infrared reflection‐absorption spectroscopy (IRRAS), quartz crystal microbalance (QCM), and tapping‐mode atomic force microscopy (TM‐AFM). These techniques deliver information about the change of the topography of the sample surfaces with emphasis on the shape and lateral distribution of the corrosion products grown within the first 1300–2800 min of weathering (TM‐AFM), as well as chemical (IRRAS) and kinetic (QCM) data. A completely different mechanism of the initial stages of atmospheric corrosion of the three investigated metals could be observed. A uniform growth of corrosion products was seen on the copper surface (identified by IRRAS and XPS to be cuprite‐like) during exposure to synthetic air with 80% relative humidity (RH), whereas the iron surface remained unattacked. The investigations of the silver surface exposed to humidity revealed that silver is attacked by humidity and tends to form oxide and hydroxide surface species. While an increased humidity content of the surrounding atmosphere causes higher corrosion rates on copper, on the exposed silver sample only a change in the degradation mechanism could be observed.The addition of SO2 to the humidified air causes the growth of so‐called ‘second‐order’ features on copper, identified to be CuSO3 · xH2O‐like, which reveals the formation of a new chemical species on the investigated surface. These features are placed on top of the homogeneous formed oxide layer and tend to form well‐defined islands. In contrast to copper, on a silver surface exposed to humidity and SO2 no new chemical species are formed; nevertheless an increased corrosion rate could be observed owing to a change of the chemistry in the physisorbed water layer. Iron exposed to humidity and SO2 still remains unattacked. An iron surface is attacked only if exposed to humidity and SO2 and NO2, which show a synergistic effect by the oxidation of four‐valent sulfur‐oxygen species by NO2. Such an attack leads to the formation of pitting corrosion, which was observed in situ and time‐resolved. The pits mainly occur on predamaged surface structures, such as scratches caused from the polishing process of the samples, and therefore promote the initiation of the corrosion. The results obtained demonstrate the high potential of the surface‐sensitive methods applied for investigating the early stages of corrosion of different metals and for obtaining a better understanding of the molecular mechanisms during degradation. Copyright © 2007 John Wiley & Sons, Ltd.

Effect of Fe–Zn alloy layer on the corrosion resistance of galvanized steel in chloride containing environments

In this study, the effect of Fe–Zn alloy layer that is formed during galvanizing process on the corrosion behavior of galvanized steel has been investigated. The galvanostatic dissolution of galvanized steel was carried out in 0.5 M NaCl solution to obtain the Fe–Zn alloy layer on the base steel. The alloy layer was characterized to be composed of FeZn 13, FeZn 7 and Fe 3Zn 10 intermetallic phases, which constitute the zeta, delta1 and gamma layers of galvanized steel, respectively. It was observed that the alloy layer has similar cathodic polarization behavior but different anodic polarization behavior compared to galvanized steel. The anodic current plateau of alloy layer was up to 100 times lower than that of galvanized coating. Corrosion test performed in wet–dry cyclic condition has shown that the alloy layer has lower corrosion rate as compared to galvanized steel. From the results of corrosion test of alloy layer and base steel, it was concluded that Zn 2+ has positive effect on the protectiveness of the zinc corrosion products. The measurement of surface potential over the alloy/steel galvanic couple has confirmed the galvanic ability of alloy layer to protect both the alloy layer itself and the base iron during initial stage of atmospheric corrosion.

Characterisation of initial atmospheric corrosion carbon steels by field exposure and laboratory simulation

The early stages of the evolution of atmospheric corrosion of carbon steels exposed in both a laboratory simulated and a natural atmosphere environment in Shenyang have been observed by in situ scanning electron microscopy. In the case of laboratory cyclic wet–dry tests, even though the chloride content level is very low, filiform corrosion is initiated in the early stage. The filiform corrosion grows in random directions, forming a network of ridges. White nodules nucleate and grow on the ridges during continued corrosion and eventually connect with each other to form the initial corrosion scale. Pits were also found on the surface beneath corrosion products. In the case of a natural atmospheric environment, both filiform corrosion and other localized corrosion, such as pitting and inter-granular attack take place in the initial stage. It is obvious that there is variety of localized corrosion in the initial stage of atmospheric corrosion.

Role of CO 2 in the initial stage of atmospheric corrosion of AZ91 magnesium alloy in the presence of NaCl

The effect of CO 2 and NaCl on the initial stage of atmospheric corrosion of AZ91 magnesium alloy was studied. The observation of surface morphology by optical microscopy (OM), scanning electron microscopy (SEM) and the analysis of corrosion products by X-ray diffraction (XRD) were integrated to investigate corrosion evolution. The results showed that NaCl stimulated the corrosion by promoting the formation of thin electrolyte film, increasing the conductivity and breaking the protective film in the absence of CO 2. The morphology of the corroded samples with deposited NaCl was more homogenous in the presence of CO 2 It was suggested that NaCl-induced corrosion was inhibited in the presence of CO 2 by the formation of slightly soluble corrosion products containing hydroxy carbonates and hydroxy chlorides that provided a partly protective layer on the surface of the magnesium alloy.

Scanning Kelvin Probe Force Microscopy: A Useful Tool for Studying Atmospheric Corrosion of MgAl Alloys In Situ

Scanning Kelvin probe force microscopy (SKPFM) is used to study the initial stages of atmospheric corrosion of an AlMg alloy and of physical vapor deposition (PVD) deposited 2 μm Al dots on pure Mg. The latter system is used as a model of a two-phase AlMg alloy. The influence of was studied in situ in humid air using SKPFM. This method allows for the in situ investigation of the evolution of the Volta potential during exposure, the resolution being in the submicrometer range. The temperature was 22.0°C, and the relative humidity was 85 or 95%. The concentration of was <1 or 350 ppm. The corrosion products were analyzed by gravimetry, ion chromatography, X-ray diffraction, scanning electron microscopy, scanning Kelvin probe, and Auger electron spectroscopy. We found that the initial stages of atmospheric corrosion on magnesium are influenced by the presence of cathodic PVD-deposited aluminum. A similar effect was seen in the case of AZ91D, the aluminum-rich β-phase forming the cathodic areas. The β-phase is nobler compared to the substrate because of the higher Al content. In the absence of the corrosion attack is localized in nature whereas the presence of ambient levels of results in a more general corrosion attack. The inhibitive effect of on the atmospheric corrosion of AZ91D is explained by the formation of a passivating layer of In the absence of the increase in pH originating from the cathodic reaction results in the dissolution of aluminum in the passive layer. A corrosion mechanism is proposed explaining the behavior in the two environments. © 2004 The Electrochemical Society. All rights reserved.

Formation and growth of micro-droplets during the initial stage of atmospheric corrosion

Formation and growth of micro-droplets during the initial stage of atmospheric corrosion

Formation and growth of micro-droplets during the initial stage of atmospheric corrosion

A droplet of sodium chloride solution placed on carbon steel spread over the surface forming tiny water micro-droplets and an expanded wet area without changing the droplet shape. The formation of the micro-droplets depended on the cation of the salt and was related to the corrosion reaction of the steel substrate. The micro-droplets contained many sodium ions and very few chloride ions and showed high pH value. Potential distribution measured by Kelvin probe indicated that the primary droplet acted as an anode and the micro-droplets and the wet area became cathodic. Potentiostatic cathodic polarization accelerated their formation and growth for NaCl solution, and the cathodic current increased with time corresponding to increment of wet area. In the case of MgCl 2, the cathodic current decreased very slowly, and wet area and micro-droplets were not observed. In the cases of ZnCl 2 and AlCl 3, the cathodic current decreased for a while depending upon the salt concentration, then increased gradually showing simultaneous formation and growth of micro-droplets. Since precipitation of hydroxides as Mg(OH) 2 and Zn(OH) 2 restrained the increase in pH, the expansion of the wet area was explained by formation of a concentrated alkaline solution of high ionic strength at the edge of the droplet and wet area.

Anodic processes on iron covered by thin, dilute electrolyte layers (II)—a.c. impedance measurements

Impedance measurements (a.c.) were performed on a planar two-electrode sample, covered with thin, dilute electrolyte layers (10 −4 and 10 −3 M Na 2SO 4, of thickness 101–1188 μm). The results obtained in this investigation confirm that the initial process of atmospheric corrosion for iron is the establishment of passivation. The establishment of initial passivation depends on the composition, concentration, and thickness of the electrolyte layer on iron. It is shown that in the initial stages of atmospheric corrosion, the corrosion rate is mainly controlled by the anodic process, i.e. the passivation of the material. The ohmic resistance polarization is not very significant.

Initial stages of atmospheric corrosion of steel in the Arabian Gulf

Energy dispersive X-ray micro-analysis, X-ray diffraction and fluorescence, Auger, X-ray photo-electron spectroscopy and Fourier transform infrared spectroscopy have been used to characterise corrosion products on carbon steel after atmospheric exposure for periods up to 12 months to an industrial environment near the west coast of the Arabian Gulf. The results indicate that atmospheric corrosion starts by the formation of small blisters at discrete locations on the metal surface, presumably the anodic sites. The blister covers are very rich in iron chlorides and contain iron oxyhydroxides, oxides, sulphates and possibly hydroxide. The formation of iron chlorides as the primary corrosion product is only limited to the early stages of blister formation due to the aggressive nature of chloride ions. Chloride formation during later stages may be partially impaired since it requires the inward transport of fresh chloride ions through the then thick rust layer. In contrast, the formation of iron sulphates at the rust-metal interface continues by the acid regeneration mechanism (which leads to the electrochemical mechanism); therefore it is less dependent on the supply of fresh sulphate ions from the surface electrolyte through the growing rust layer.