Corrosion Of Steel Surface Research Articles

The role of structural chemistry in the inhibitive performance of some aminopyrimidines on the corrosion of steel

Abstract Corrosion inhibitive performance of 2-aminopyrimidine (APr), 2,4-diaminopyrimidine (dAPr), 2,4-diamino-6-hydroxy-pyrimidine (dAHPr) and 2,4,6-triaminopyrimidine (tAPr) during the acidic corrosion of steel surface was investigated using three methods, MP2, ab initio Hartree–Fock and density functional theory (DFT). Quantum chemical parameters such as the highest occupied molecular orbital energy ( E HOMO ), the lowest unoccupied molecular orbital energy ( E LUMO ), energy gap (Δ E ), dipole moment ( μ ), sum of the total negative charge (TNC), molecular volume (MV), electronegativity ( χ ), chemical potential (Pi), global hardness ( η ), softness ( σ ) and the fraction of electrons transferred (Δ N ), were calculated. Furthermore, the interaction energies of the inhibitors with the iron surface were studied. A good correlation was found between the theoretical data and the experimental results.

Cathodic delamination: Quantification of ionic transport rates along coating–steel interfaces

So-called cathodic delamination is one of the major modes of failure for organic coatings immersed in electrolyte solutions (e.g. seawater). Cathodic delamination occurs as a result of the electrochemical reactions, which takes place on a corroding steel surface. This means that reactants must continuously be transported from the bulk solution to the cathodic areas. The transport of sodium ions from a defect in the coating to the cathodic areas is generally considered the rate-determining step for cathodic delamination because the transport of oxygen and water through the coating is sufficient for the corrosion processes. In this work, a novel practical method, which allows direct estimation of the apparent diffusion coefficient of sodium ions in the ultrathin aqueous layer at the coating–steel interface, is described. The apparent diffusion coefficients estimated are of similar magnitude as previously reported values and show an acceptable repeatability. The method was used to obtain the apparent diffusion coefficients of sodium ions in the coating–steel interface for three commercial inert-pigmented epoxy coatings. The delamination rates predicted using the apparent interfacial diffusion coefficients and Fick's second law, under the assumption of a transport-controlled mechanism, show qualitative agreement with the observed delamination rates in 0.5 M sodium chloride. This confirms that the rate-determining step of cathodic delamination is the transport of sodium ions along the coating–steel interface.

Influence of Paint Type on Steel Corrosion for Marine Applications (Dept.M)

The majority of naval ships are constructed of mild steel. Corrosion is a major concern in a maritime environment. This particular type of material degradation has recently received more attention by the marine industry. The present work aims to investigate the effect of recent coatings used in marine ship surfaces for preventing corrosion. Experiments were performed according to standard tests to evaluate and measure the coating adhesion to steel and to measure the corrosion wear rate if any for three types of coatings. An accelerated corrosion test was conducted to duplicate in the laboratory the field corrosion performance of a product. The results indicate that all under investigated types of paint have resulted in a reduction in the corrosion rate compared with the uncoated steel. A minimum corrosion rate of 0.8 mm/year was obtained for the coat Hempadur 52140 compared to 2.1 mm/year for the uncoated steel. A microscopic examination of the corroded steel surfaces was conducted which prevailed pitting behavior with different degree. The minimum corroded surface exhibited few pitting attack in comparison to other specimens. Although the pitting attack of the surface layer (paint), one can drive a conclusion that sample surface without coating is aggressively attacked by pits.

Cathodic delamination: Quantification of ionic transport rates along coating–steel interfaces

So-called cathodic delamination is one of the major modes of failure for organic coatings immersed in electrolyte solutions (e.g. seawater). Cathodic delamination occurs as a result of the electrochemical reactions, which takes place on a corroding steel surface. This means that reactants must continuously be transported from the bulk solution to the cathodic areas. The transport of sodium ions from a defect in the coating to the cathodic areas is generally considered the rate-determining step for cathodic delamination because the transport of oxygen and water through the coating is sufficient for the corrosion processes. In this work, a novel practical method, which allows direct estimation of the apparent diffusion coefficient of sodium ions in the ultrathin aqueous layer at the coating–steel interface, is described. The apparent diffusion coefficients estimated are of similar magnitude as previously reported values and show an acceptable repeatability. The method was used to obtain the apparent diffusion coefficients of sodium ions in the coating–steel interface for three commercial inert-pigmented epoxy coatings. The delamination rates predicted using the apparent interfacial diffusion coefficients and Fick's second law, under the assumption of a transport controlled mechanism, show qualitative agreement with the observed delamination rates in 0.5 M sodium chloride. This confirms that the rate-determining step of cathodic delamination is the transport of sodium ions along the coating–steel interface.

The Characterization of Some Steel Corrosion Products by FT-IR Spectroscopy

The present work is a continuation of our precedent studies [1, 2] as an attempt to characterize the corrosion products formed on the carbon steel (OL 37) exposed to natural and artificial environments, both having high relative humidity and chloride content. Samples of steel sheets of 200 . 100 . 2 mm dimension were prepared using abrasive blasting with specific requirements. As natural and artificial environment, a marine experiment site, respectively a salt spray test with specific exposure conditions, were used. Iron oxyhydroxides and oxides are typical constituents of rust, generated by the corrosion of steel surface in contact with aqueous phase [3, 4]. The phase composition of the rust depends on the physic-chemical factors from the environment such as: type of steel, time of exposure, electrolyte composition, pH and temperature [5, 6]. The composition and structure of carbon steel corrosion products for the two situations (accelerated lab and real conditions) were studied comparatively using an adequate FT-IR spectroscopy method and KBr pellets technique. The FT-IR spectrometer operates with OPUS program.

Real-time corrosion mapping of steel surfaces using an optoelectronic instrument based on lightwave scattering

The application of an optoelectronic-sensor-based virtual instrument designed by the authors, for visualising and estimating the degree of corrosion of steel surfaces exposed to different concentrations of sulphuric acid, is reported. The optoelectronic sensor consisting of a light-emitting diode (LED) and a pair of photo detectors was fixed very close to the sample placed on a stepper motor-driven moving platform so that the sample surface may be scanned by a thin light beam from the LED. The reflected and scattered light signals from each point in the scanned area were acquired separately by the two detectors in the sensor module. A parameter incorporating the relative value of these signals proved to be a fairly reliable measure of the degree of corrosion. The corrosion factor values were computed by a personal computer and presented in the form of a three-dimensional graph. The average values of the corrosion factor for different steel samples were plotted against the concentration levels of the corroding agent. The variation of the corrosion factor was found to obey a bilogarithmic law, which was in conformity with the previous results.

Corrosion of reinforcing steel and low cycle fatigue behaviour

AbstractChloride induced corrosion of reinforcing steel can be highly detrimental and of great influence on the low cycle fatigue (LCF) characteristics. An experimental study conducted on BSt500s reinforcing steel, showed that the LCF and life expectancy were reduced considerably according to the level of corrosion. Low cycle strain controlled fatigue testing under ± 1 and ± 2.5% constant amplitude strain indicated that the corroded steel bars exhibit gradual reduction in available energy, number of cycles to failure and the load bearing ability. Formation of irregularities such as pits, notches and cavities occurred on the corroded steel surface and stress concentration points were developed which are highly localized at imperfections and especially at the rib bases. The experimental investigation of the corroded specimens subjected to LCF showed that the life expectancy, the remaining energy density and the strength properties were reduced considerably as a result of these irregularities combined with the mass loss and reduction of the exterior hard layer of martensite. Structural design capable of resisting seismic activity that does not account for the reduction of the load bearing ability and life expectancy as well as the cumulative plastic deformation of the steel reinforcement due to corrosion and loading history that a structure will be subjected in harsh climatic environments and ground oscillating motion could lead to serious and unpredictable performance.

Mechanical Properties of Reinforcing Steel and Fatigue Behavior in Corrosive Environment

Corrosion of reinforcing steel has a great impact on the mass reduction and high- and low-cycle fatigue. An experimental study showed that the mass loss, the fatigue limit and the life expectancy were reduced by approximately 1.50-3.00%, 20-40%, and 55-75%, respectively, according to the level of corrosion. Low-cycle strain controlled fatigue testing under ±1% and ±2.5% constant amplitude strain, indicated that the corroded steel bars exhibit gradual reduction in available energy, number of cycles to failure and the load-bearing ability. Formation of pits and notches took place on the corroded steel surface and stress concentration points were developed which are highly localized at imperfections and especially at the rib bases. The fatigue limit was reduced considerably since the existence of ribs and the formation of pits and notches combined with the mass loss led to reduction of the exterior hard layer of martensite and drastic drop in the energy density of the corroded specimens. Antiseismic design that does not take into account the maximum and cumulative plastic deformation demands and the strain history that a structure will suffer under severe ground motion could lead to unpredictable performance.

An in situ electrochemical impedance spectroscopy/synchrotron radiation grazing incidence X-ray diffraction study of the influence of acetate on the carbon dioxide corrosion of mild steel

A combination of electrochemical impedance spectroscopy (EIS) and in situ synchrotron radiation grazing incidence X-ray diffraction (SR-GIXRD) has been used to study the influence of acetate on the carbon dioxide corrosion of mild steel. The SR-GIXRD data demonstrated that normal corrosion – in a carbon dioxide saturated brine – induced the formation of a thick corrosion scale of Fe 2(OH) 2CO 3 and Fe 2O 2CO 3, and this totally obscured the α-Fe diffraction peaks of the underlying steel substrate after 24 h. On the other hand, the carbon dioxide corrosion of mild steel in the presence of acetate also detected the Bragg diffraction peaks for Fe 2(OH) 2CO 3 and Fe 2O 2CO 3; however, the α-Fe diffraction peaks of the underlying steel substrate were not extinguished with time, and there was a reversal in the pattern of evolution of the intensities of the Fe 2(OH) 2CO 3 and Fe 2O 2CO 3 phases in acetate. Accordingly, the EIS data showed a poorly defined medium frequency time constant for the corroded steel specimen in brine spiked with acetate, and this medium frequency time constant was extinguished as a function of time. Alternatively, EIS of the corroded specimen also revealed a medium frequency time constant after 24 h. In addition, EIS complex–plane impedance plots showed that the corroded electrode had become passivated in an acetate-spiked brine, as evidenced by a three-fold enhancement in the charge transfer resistance at low frequency. These EIS/SR-GIXRD outcomes suggest that acetate affects the crystallization chemistry of the Fe 2(OH) 2CO 3/Fe 2O 2CO 3 corrosion scale, and this causes a mild passivation of the corroded steel surface.

Modelling deterioration of structural behaviour of reinforced concrete beams under saline environment corrosion

In the assessment of existing structures the likely future deterioration of strength and stiffness is of interest. For reinforced concrete beams one of the most important influencing factors is the loss of reinforcement cross-sectional area at critical locations. Because corrosion is a long-term process for well-designed structures, there is only limited field experience available on which to draw and with which to make empirical rules. The considerable research effort in corrosion of reinforcement in concrete structures has focused mainly on the rate of migration of chloride ions from the environment through the concrete to the corroding steel surface. This will estimate the time before reinforcement corrosion becomes significant but does not provide the rate of structural deterioration. In the present paper a method is proposed for estimating structural deterioration, based on evidence that (a) reinforcement corrosion causes internal damage to and loss of bond with the surrounding concrete and (b) chloride diffusion is influenced by stresses set up in the concrete by external loading. Both these factors affect the rate of chloride migration locally and hence the amount of corrosion and material strength loss at any point in time. The proposed method is outlined and an example application given. Reasonably good agreement between the results of the proposed procedure and the few experimental results was obtained.

PH-Microscopy: technical application in phosphating solutions

The applicability of the pH-microscopy with microelectrodes based on H +-ion-selective liquid membranes is shown for phosphating solutions. Linear potential response is found at room temperature up to 60 °C with Nernst factors of −58 and −69 mV/pH, respectively. The investigation of an electrode surface activity by pH-imaging is demonstrated with surface scans above special designed test electrodes. The formation of pH-gradients due to the corrosion of steel in diluted phosphoric acid is examined in dependence on nitrite (accelerator) concentration, time and distance to the corroding surface ΔpH= f(c NO 2 , t, z). In a distance of 1 μm above the corroding steel surface the pH-shift within 100 s is ΔpH=0.08 with c(NaNO 2)=2.9 mM. The pH-shift increases up to ΔpH=0.8 with c(NaNO 2)=11.6 mM. The simulation of corrosion caused pH-gradients by electrochemical generated pH-gradients on an inert microdisk electrode allows the quantitative determination of the additional H +-consumption by nitrite. Therefore, the theory of spherical steady-state diffusion fields around microdisk electrodes is used.

In situ SERS study of the adsorption of inhibitors of carbon dioxide corrosion

AbstractA specially designed electrochemical cell incorporating a rotating disc electrode has been used for in situ surface‐enhanced Raman spectroscopy (SERS) studies of the adsorption of inhibitors of carbon dioxide corrosion onto silver‐coated mild steel electrodes. It is shown that SERS‐active inhibitors comprising aromatic moieties may be detected using the SERS technique. Furthermore, the efficacy of adsorption of corrosion inhibitors employed in the present study is optimal near the open cell or corrosion potential, demonstrating that electrode polarization induces electrostatic forces of repulsion that retard the adsorption of the inhibitor to the corroding steel surface. Copyright © 2003 John Wiley & Sons, Ltd.

Contribution of organic and mineral compounds to the formation of solid deposits inside petroleum wells

Deposit samples collected from three Mexican wells, their asphaltene and residue fractions as well as the sediment and asphaltene fractions separated from the corresponding crude oils were characterized. An appreciable amount of minerals such as CaCO 3, BaSO 4, NaCl, quartz and iron compounds were detected in the deposit compositions. Additionally, aromatic factors and structural parameters such as interlayer distance and crystallite diameters were calculated from the ( γ) and (002) characteristic bands from the X-ray diffractograms of the deposits, deposit-asphaltene, oil-asphaltenes as well as oil-sediments. FTIR, elemental analysis and thermal techniques were also used to elucidate the sample compositions. The stages of the deposit formation inside petroleum wells include steel surface corrosion products formed in situ by the presence of brine and sulfur bearing compounds and adsorption or chemisorption of organic compounds on the modified tubing steel surface and mineral pores. Moreover, the high amount of vanadium and nickel indicates a time-dependent process of accumulation of some organometallic compounds independent of the oil-asphaltene amount.

Influence of Copper Content of the Base Steel on the Corrosion Behavior of Nickel-coated Steel Sheets.

Influence of copper content in a base steel on corrosion resistance of a nickel-coated steel sheet in solutions as strongly corrosive high-acid beverage has been studied, and the following facts were revealed: Copper addition to the base steel greatly improves the corrosion resistance of the nickel-coated steel sheet in the citric acid and sodium chloride solution. This improvement is resulted from a reduction in the couple current between the nickel and the base steel in the pinholes formed in the nickel coating layer. The reduction in the couple current is considered to arise from shifting corrosion potential of the copper-added steel to the noble direction and increasing in anodic polarization. The enrichment of copper on the corroded steel surface is considered to bring about great changes in electrochemical properties. The decrease in the couple current between the nickel and the base steel is also obtained under the variation of an area ratio of anode to cathode. Copper addition to the base steel also gives high corrosion resistance to the nickel-coated steel sheet in the simulated beverages, such as those containing citric acid, citric acid and sodium chloride, malic acid and, lactic acid except containing phosphoric acid.

The Electrochemical Response of Steel to the Presence of Dissolved Cerium

A vibrating probe technique for measuring the current density distribution over a corroding steel surface has been used to investigate corrosion inhibition by cerium salts. The probe vibrations enabled the current magnitude and direction in a plane perpendicular to the steel surface to be measured. Contrary to published data, it has been concluded that, at least for steels, cerium acts as an anodic inhibitor.

Analysis for lithium by secondary ion mass spectrometry (SIMS) on corroded steel surfaces

Abstract The steel AISI 316 is inert to the tritium breeders Li2O, Li2SiO3 and metallic Li except in the presence of impurities or at very high temperatures. Under these conditions the steel can be corroded severely, and SIMS is uniquely suitable for detecting the Li distribution. Corroded steel surfaces have been analysed by SIMS, and when the technique is complemented by Scanning Electron Microscopy with Energy Dispersive X-ray Analysis (SEM/EDAX), and X-Ray Diffraction (XRD), it is seen that both solid (Li2O, Li2SiO3) and liquid (Li) potential tritium breeders (for fusion devices) corrode the steel similarly. The steel is penetrated by Li+ ions together with the corresponding anions via grain boundaries and Cr is extracted from the grains to give Cr-depleted steel ( = Fe Ni ). A stable ternary compound (LiCrO2 with Li2O and Li2SiO3; Li9CrN5 with Li/Li3N) is formed in the grain boundaries and also as a layer on the steel surface. This type of corrosion alters the surface composition of the steel and the intergranular penetration is the precursor to steel fracture.

Discussion on “Utilization of the Specific Pseudocapacitance for Determination of the Area of Corroding Steel Surfaces”

Abstract The following article is a discussion of the paper entitled “Utilization of the Specific Pseudocapacitance for Determination of the Area of Corroding Steel Surfaces,” by J.N. Murray, P.J. ...

Utilization of the Specific Pseudocapacitance for Determination of the Area of Corroding Steel Surfaces

Abstract Determination of the capacitance of a corroding metal-electrolyte interface offers the possibility of an independent measurement of the area of the corroding metal. This in turn allows for the evaluation of the corrosion rate from the current calculated from the measured polarization resistance (ΔV/ΔI). Low carbon steel in fully aerated 1 M sodium sulfate solution was investigated using electrochemical impedance spectroscopy (EIS) to evaluate the interfacial capacitance as well as the polarization and ohmic resistances. The value of the capacitance per surface area unit was determined with samples ranging from 0.5 to 40 cm2 over periods of up to 1000 h. The capacitance values changed quite rapidly during the first 72 h while the local chemistry and corrosion potential were stabilizing and then slowly increased to a stable level in ∼500 h. A specific capacitance of ∼200 µF/cm2 was determined and is being applied to polarization resistance values from buried gas transmission pipeline samples to det...

Citric acid augmented flashlamp cleaning of corroded steel surfaces

Due in large part to its environmental acceptability, solutions of citric acid are used to effectively attack and dissolve rust while maintaining the integrity of the base metal. However, the need for high temperatures and solution additives poses constraints. We have recently demonstrated an improved method of rust removal that synergistically employs the high intensity light output of a flashlamp together with a thin layer of citric acid solution. Such a combination will remove rust from steel surfaces as effectively as conventional citric acid cleaning, but at an increased rate. The short, intense burst of radiation in conjunction with the chelating properties of the citric acid acts to explosively remove surface oxide layers. Microscopic surface analysis (scanning electron microscopy and X-ray diffractometry) reveals conversion of red hematite to black magnetite during the irradiation process. Subsequent applications of the treatment serve to completely remove the magnetite leaving a clean metal surface. Optical radiation cleaning of steel surfaces offers several advantages: ambient temperature citric acid solutions are used in small quantities, organic surface contaminants are removed in the process, and an increased resistance of the cleaned surface towards flash rusting. Details of the flashcleaning process and examples of treated surfaces will be presented in this paper.

Recent advances in molten salts as reaction media

Abstract