Oxidation of 1018 carbon steel in borate medium by in situ EC-STM: Surface morphology of the oxidized ferrite and pearlite phases (original) (raw)
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Journal of The Electrochemical Society, 2005
The mechanism and progress of oxidation of the pearlite phase of 1018 carbon steel in contact with a borate medium was monitored and characterized using the in situ electrochemical scanning tunneling microscopy ͑ECSTM͒ technique. The pearlite phase was identified by characteristic microstructure using a previous experimental methodology. The progress of the pearlite oxidation due to differently imposed anodic potential was monitored via change of the electrode surface morphology. ECSTM images indicate two types of the iron oxide formation on the pearlite surface, with different and distinguished morphology.
Oxidation of Co- and Ce-nanocoated FeCr steels: A microstructural investigation
Surface and Coatings Technology, 2013
The effect of novel Co and Ce nanocoatings on oxidation behaviour and chromium volatilization from a commercial Fe-22Cr steel (Sanergy HT) developed for solid oxide fuel cell interconnect applications is investigated. Three different coatings (10 nm Ce, 640 nm Co and 10 nm Ce + 640 nm Co) are studied. Uncoated and nanocoated samples are exposed isothermally at 850°C in the air with 3% H 2 O for 168 h. The detailed microstructure of the different coatings is investigated. The surface morphology and microstructure of the oxide scales are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX). Cross-section TEM thin foils are prepared by using a combined FIB/SEM (focused ion beam/scanning electron microscope) instrument. A 640 nm cobalt coating strongly inhibits Cr volatilization but has only minor effects on oxidation rate. In contrast, a 10 nm Ce coating decreases the oxidation rate but has no significant effects on chromium volatilization. Combining the two coatings, i.e., applying a 640 nm Co coating on top of the 10 nm Ce, effectively reduces Cr evaporation and slows down the rate of alloy oxidation.
On the Use of the Scanning Electrochemical Microscopy in Corrosion Research
Solid State Phenomena, 2015
This paper deals with the basic theory and the usability of Scanning Electrochemical Microscopy (SECM) in corrosion research. The SECM is the in situ method of surface characterization which is based on the scanning of the tested surface using ultramicroelectrode and simultaneous electrochemical testing of the surface. This technique provides an electrochemical imaging of the surface. Key applications of SECM have been demonstrated based on the newest literature data covering the past two years of the active research in the field of corrosion in a nanoscale.
Materials, 2015
The aim of this research was to investigate the influence of metallurgy on the corrosion behaviour of separate weld zone (WZ) and parent plate (PP) regions of X65 pipeline steel in a solution of deionised water saturated with CO2, at two different temperatures (55 °C and 80 °C) and at initial pH~4.0. In addition, a non-electrochemical immersion experiment was also performed at 80 °C in CO2, on a sample portion of X65 pipeline containing part of a weld section, together with adjacent heat affected zones (HAZ) and parent material. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion behaviour of the separate weld and parent plate samples. This study seeks to understand the significance of the different microstructures within the different zones of the welded X65 pipe in CO2 environments on corrosion performance; with particular attention given to the formation of surface scales; and their composition/significance. The results obtained from grazing incidence X-ray diffraction (GIXRD) measurements suggest that, post immersion, the parent plate substrate is scale free, with only features arising from ferrite (α-Fe) and cementite (Fe3C) apparent. In contrast, at 80 °C, GIXRD from the weld zone substrate, and weld zone/heat affected zone of the non-electrochemical sample indicates the presence of siderite (FeCO3) and chukanovite (Fe2CO3(OH)2) phases. Scanning Electron Microscopy (SEM) on this surface confirmed the presence of characteristic discrete cubeshaped crystallites of siderite together with plate-like clusters of chukanovite.
2015
The aim of this research was to investigate the influence of metallurgy on the corrosion behaviour of separate weld zone (WZ) and parent plate (PP) regions of X65 pipeline steel in a solution of deionised water saturated with CO2, at two different temperatures (55 °C and 80 °C) and at initial pH~4.0. In addition, a non-electrochemical immersion experiment was also performed at 80 °C in CO2, on a sample portion of X65 pipeline containing part of a weld section, together with adjacent heat affected zones (HAZ) and parent material. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion behaviour of the separate weld and parent plate samples. This study seeks to understand the significance of the different microstructures within the different zones of the welded X65 pipe in CO2 environments on corrosion performance; with particular attention given to the formation of surface scales; and their composition/significance. The results obtained from grazing incidence X-ray diffraction (GIXRD) measurements suggest that, post immersion, the parent plate substrate is scale free, with only features arising from ferrite (α-Fe) and cementite (Fe3C) apparent. In contrast, at 80 °C, GIXRD from the weld zone substrate, and weld zone/heat affected zone of the non-electrochemical sample indicates the presence of siderite (FeCO3) and chukanovite (Fe2CO3(OH)2) phases. Scanning Electron Microscopy (SEM) on this surface confirmed the presence of characteristic discrete cubeshaped crystallites of siderite together with plate-like clusters of chukanovite.
CORROSION, 1996
The fine-grained structural steel DIN W.Nr. 1.0566 was exposed to various sulfate and chloride-containing aqueous solutions, the latter ones simulating the potential accidental environment of water intrusion into a salt mine. By electrochemical measurements in salt brines, the following results were achieved: (1) The corrosion rate is highly dependent on salt brine composition, pH and temperature. (2) Active metal dissolution led to formation of shallow pits as surface corrosion phenomenon. Thus, the application of electrochemical techniques-under non-polarized as well as under potentiodynamic conditions-proved to be suitable for fast qualitative testing of the influence of various environmental parameters on steel corrosion
Corrosion Science, 2001
In this study the dierent surface states that manifest in the corrosion process of 1018 carbon steel in alkaline sour environment, solution prepared speci®cally to mimic the sour waters occurring in the catalytic oil re®nery plants of the Mexican Oil Company (PEMEX) (0.1 M (NH 4 ) 2 S and 10 ppm NaCN at pH 9.2) were prepared and characterized. The surface states of the carbon steel were formed by treating the surface with cyclic voltammetry at dierent switching potentials (E k ), commencing at the corrosion potential (E corr À0:890 V vs sulfate saturated electrode, SSE). The surface states thus obtained were characterized using electrochemical impedance spectroscopy and scanning electron microscopy techniques. It was found that for E k À0:7 and À0:6 V vs SSE a ®rst product of corrosion formed, characterized by a high passivity. Moreover, it was very compact (with a thickness of 0.047 lm). However, at more anodic potentials (E k > À0:5 V vs SSE) a second corrosion product with non-protective properties (porous with a thickness of 0.4 lm and very active) was observed. The diusion of atomic hydrogen (H 0 ) was identi®ed as the slowest step in the carbon steel corrosion process in the alkaline sour media. The H 0 diusion coecients in the ®rst and second products that formed at the carbon steel±sour medium interface were of the order of 10 À15 and 10 À12 cm 2 /s respectively. Ó
Uses of scanning electrochemical microscopy in corrosion research
In: “Microscopy: Science, Technology, Applications and Education”. Volume 3. A. Méndez-Vilas, J. Díaz (editors). Formatex Research Center, Badajoz, pp. 1769-1780 (2010). , 2010
This paper provides a brief review of a relatively new technique, namely scanning electrochemical microscopy (SECM), and its applications in measuring, characterising and evaluating corroding systems. Localized corrosion processes and electrochemical activity distributions in surfaces can thus be investigated in real time with high spatial resolution. The SECM is a unique near-field scanning technique that is electrochemically integrated as to detect chemical and electrochemical activities in electrochemical heterogeneous systems such as those operating in corrosion research. The SECM can be used in a variety of ways, which can be broadly classified into amperometric and potentiometric modes, depending on the type of the sensing probe, namely an ultramicroelectrode (UME) and an ion-selective microelectrode, respectively. The operation modes of the instrument are described together with typical experiments selected to illustrate their application in sensing localised corrosion.
Electrochimica Acta, 2012
An integrated SKP-SECM system was successfully optimised with respect to improved lateral resolution. An aluminum alloy was synthesised by solidification of a liquid melt of pure Al, Cu and Mg metal powders in order to visualize single S-phase intermetallic particles (IMPs) using a newly proposed "glass free" SKP-SECM tip. The obtained IMPs were randomly distributed in the solid solution matrix of the alloy and their average chemical composition was in agreement with that of S-phase IMPs in commercially available AA2024-T351 alloys. The S-phase IMPs were localized in the SKP mode of the SKP-SECM system. The increased electrochemical activity of the S-phase IMPs was visualized using the feedback mode of SECM and the in situ consumption of O 2 on the surface of a single S-phase IMP was visualized in the redoxcompetition mode of the SECM using the same tip. Thus, the local Volta potential difference obtained in the SKP mode could be overlaid with the local electrochemical activity for O 2 reduction.