Corrosion studies of carbon steel X60 by electrochemical methods (original) (raw)
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Materials Research, 2013
X52 and X60 high strength low alloy (HSLA) steels are widely used in the construction of petroleum pipelines. This paper discusses the corrosion resistance of X52 and X60 steels in CO 2 containing saltwater at pH 4.4 and 50 °C. A circulating flow loop system inside an autoclave was used for conducting the experimental work. The rotating impeller speed was 2000 rpm. The corrosion rate was monitored using in situ electrochemical methods such as potentiodynamic sweep, linear polarization resistance, and electrochemical impedance spectroscopy (EIS) methods. Results indicated that the corrosion rate of X60 steel is relatively higher than that of X52 steel.
Corrosion, 2013
The corrosion behavior of API 5L-X65 carbon steel in a carbon dioxide (CO 2)-saturated solution was investigated by electrochemical measurements (polarization curves, Levich plots, and electrochemical impedance spectroscopy) with a rotating disk electrode. Different experimental conditions such as hydrodynamics, immersion time, and temperature were considered. From the polarization curves, it was shown that both the anodic and cathodic current densities decreased as the electrode rotation speed, the immersion time, and the temperature increased. This behavior was in agreement with the impedance results obtained at the corrosion potential. It was shown that the corrosion processes were initially controlled by mass transport but they became under activation control for longer immersion times. Scanning electron microscopy was used to characterize the corrosion products. For short immersion times (2 h and 6 h), the corrosion products mainly deposited on the cathodic sites (pearlitic zones) of the carbon steel surface forming a heterogeneous layer, whereas they covered the whole electrode surface after longer periods (>15 h). At a microscale, localized corrosion, as a result of galvanic coupling between pearlite and ferrite, was also observed.
Materials Sciences and Applications, 2011
The corrosion behavior of 1020C carbon steel samples that had been subjected to oxidizing heat treatment at 550˚C and 675˚C were studied in sodium chloride electrolytes using a 3-electrode electrochemical impedance spectroscopy. Experimental data were used to evaluate the corrosion behavior of the samples while optical microscopy was employed to investigate the surface characteristics of the samples before and after aqueous corrosion. The results showed that while the sample treated at 550˚C revealed an increasing corrosion rate with time, the sample treated at 675˚C indicated a higher initial corrosion rate, but the rate declined gradually over the 4-day experimental period. Optical microscopy revealed significant formation of surface corrosion products on both heat treated samples, but the complex plane diagrams indicated significant capacitive behavior for the heat treated samples relative to the untreated samples.
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
Journal of Solid State Electrochemistry, 2003
The study of a plain carbon steel (AISI 1020) in Na 2 SO 4 aqueous solutions at different concentrations was carried out by electrochemical impedance spectroscopy (EIS) in order to determine the corrosion mechanism and to obtain representative corrosion rates of the system. EIS was used to measure corrosion current densities at high concentrations in the range 0.1-1 wt% Na 2 SO 4 , but in the low concentration range, from 0.001 to 0.01 wt%, a scattered Nyquist plot was obtained. Other electrochemical techniques, such as polarization resistance (PR), Tafel plots and electrochemical noise (EN), were also used in this analysis. The charge transfer resistance was determined and compared with the PR and noise resistance.
Electrochimica Acta, 2000
We evaluated the corrosion process of 1018 carbon steel in an alkaline sour environment, using a very specific solution to simulate the conditions of the sour waters occurring in the catalytic plants of the PEMEX (Mexican Oil Company) oil refinery, 0.1 M (NH 4) 2 S and 10 ppm NaCN at pH 9.2. Using polarization curves and electrochemical impedance spectroscopy, we characterized the carbon steel surfaces following diverse immersion times in the alkaline sour environment. The corrosion process in these media involves a series of steps occurring simultaneously. At initial immersion times, the corrosion rate is rapid and a protective film of maximum thickness forms. After 50 h of immersion, growth and dissolution of the film reach equilibrium. As the protective film is formed from corrosion products, different diffusing processes occur through it. Fe 2 + ions and atomic hydrogen (H o) diffuse through the film. The diffusion of atomic hydrogen is the limiting step of the corrosion process. An accelerated assay of the corrosion process shows that diffusion of atomic hydrogen causes the rupture (blister) of the passive film formed in these media, increasing H o diffusion up to a critical time where the corrosion process increases.
Surface and Electrochemical Behaviour of Carbon Steel in Neutral aqueous Environment
Corrosion inhibiton of Carbon Steel immersed in 60 ppm Cl- has been investigated in presence and absence of Zn2+ ions. The Weight – loss method is used to find the Inhibition Efficiency of the inhibitors. The formulation consists of 50 ppm of DTPMP, 10 ppm of Sodium Molybdate (SM), 10 ppm Zn2+ and it gives the maximum IE of 90%. When inhibitors used alone that gives some IE. But their combination in particular proportion shows the maximum IE is otherwise called as Synergistic Effect. The Electrochemical impedance spectroscopy (EIS) indicates that the formation of protective film on the surface of metal. The Atomic Force Microscopy also confirms the formation of film by the way of increasing in smoothness of the surface of Carbon Steel.
Electrochemical corrosion behavior of X80 pipeline steel in a near-neutral pH solution
Mater Corros, 2009
In this work, the electrochemical corrosion behavior of X80 pipeline steel was investigated in a near-neutral pH solution using electrochemical impedance spectroscopy (EIC) and photo-electrochemical (PEC) measurements as well as X-ray photo-electron spectroscopy (XPS) technique. The effects of hydrogencharging and stress were considered. The results show that the steel is in an active dissolution state, and a layer of corrosion product is formed and deposited on the electrode surface, which is subjected to further oxidation to form ferric oxide and hydroxide. Photo-illumination enhances anodic dissolution of the steel when it is under anodic polarization due to destroying of the corrosion product film. When the steel is under cathodic polarization, the cathodic current density decreases upon laser illumination due to the photo-oxidation of hydrogen atoms generated during cathodic reactions, which behaves as an anodic reaction to offset the cathodic current density. Hydrogen-charging and stress decrease the corrosion resistance of the steel and enhance the dissolution rate of the steel.
Corrosion Science, 2007
Corrosion of carbon steel in un-buffered NaCl solutions was studied applying linear potential sweep technique to a rotating disk electrode. Current–potential curves were obtained from linear potential sweep at a rate of 1 mV s−1 in solution with concentrations in the range 0.02–1 M NaCl and rotation rates in the range 170–370 rad s−1, at 22 °C. Potential sweeps, which were conducted in the potential range −700 to −100 mV/SHE, were started from the cathodic limit in order to approach the measurement of corrosion under rust-free conditions. Polarization curves were analyzed with a superimposition model developed ad hoc and implemented in a computer program, which enabled determining the corrosion rate and kinetics parameters of the underlying anodic and cathodic sub-processes. The anodic sub-process, dissolution of iron, was well described in terms of a pure charge transfer controlled reaction, while the cathodic sub-process, oxygen reduction on iron, was well described in terms of mixed mass transfer and charge transfer control. Increase of electrode rotation rate increases the limiting current of oxygen reduction, which results in an enhanced corrosion rate of carbon steel. Increase of NaCl concentration has a dual effect: the limiting current of oxygen reduction decreases as a result of the influence of NaCl concentration on solution viscosity and the anodic dissolution of iron increases due to the influence of NaCl on pitting formation. However, this last mechanism predominates and a net increase in carbon steel corrosion rate is observed in this case.