Uniform Corrosion Rate Research Articles

Preliminary results of corrosion monitoring studies of carbon steel overpack exposed to supercontainer concrete buffer

The supercontainer (SC) is the reference concept for the postconditioning of vitrified high level radioactive waste and spent fuel in Belgium. It is designed with a concrete buffer completely surrounding a carbon steel overpack. A half-scale (HST-2) experiment was set up to measure the instantaneous uniform corrosion rate, representative of the initial oxic phase, in situ. The test set-up has the same diameter as a full size SC, but it is limited in height to approximately half of a real SC. The corrosion rate of carbon steel is measured in four ways: weight loss measurements (carbon steel coupons), corrosion sensor based on linear polarisation resistance, corrosion sensor based on multisine electrochemical impedance spectroscopy and corrosion sensor based on single sine electrochemical impedance spectroscopy coupled to a unique analytical method. This paper presents the preliminary results of the corrosion rates measured with these independent methods.

Corrosion behaviours of novel Mg–13Li–X alloy fabricated by rapid solidification process

As degradable biomaterials, the higher degradation rate in a physiological environment is the main challenge for the application of magnesium alloys. For this reason, the effect of the rapid solidification processing (RSP) on the corrosion resistance of Mg–13Li–3Al–1Zn–0·5Sr–0·5Ca (Mg–13Li–X) was studied using electrochemical techniques at the corrosion potential (Ecorr). The alloy with a chemical composition of Mg–13Li–X was prepared, melted and cast in a low carbon steel crucible under a protective gas of Ar, then melted two to four times to ensure compositional homogeneity. Rods with diameters of 1, 3 and 6 mm were prepared by a rapid solidification process. Uniform corrosion rates were measured at 37±0·5°C, which is equal to the normal human body temperature, in a pH 7·2–7·4 Hank’s balanced salt solution (HBSS) adjusted by HCl and NaOH using electrochemical impedance spectroscopy. The surface morphologies of experimental samples before and after the corrosion in Hank’s solution were characterised by scanning electron microscopy (SEM) observation complemented by energy disperse spectrometer (EDS) analysis. The results show that the corrosion behaviours of the magnesium–lithium alloys are significantly influenced by the rapid solidification process. The RSP treated samples led to higher impedance and polarisation values than conventional Mg–13Li–X alloy and AZ31 and AZ91. The minimum corrosion current density of Ö6 species was 13·92 μA cm−2. And the corrosion potential (Ecorr) was −0·326 V, moved about 1 V towards noble compared to AZ31 (−1·46 V), AZ91 (−1·36 V) and JDBM (−1·79 V). The results indicated that RSP could increase their polarisation resistance and reduce the corrosion current densities, increase the corrosion resistance and promote the surface passivation in turn. The results suggest that the novel RSP Mg–13Li–X alloy can be considered for in-depth research in vitro corrosion environment.

Optical measurement of uniform and localized corrosion of C1018, SS 410, and Inconel 825 alloys using white light interferometry

We describe the use of a vertical scanning interferometer (VSI) to quantitatively measure the uniform and localized corrosion rates of different metal alloys used in the oil and gas industry. Based on white light interferometry, the most significant advantage is the large field of view in combination with nanometer Z-resolution for fast and accurate surface measurements. Corrosion rates were calculated directly from VSI data and verified by weight loss analysis. We explored the quantitative impact of high temperature and high salinity on C1018, SS 410 and I-825 alloys. VSI data for uniform corrosion correlated well with data from weight loss analysis.

On the stress corrosion cracking of lean duplex steel in chloride environment

Duplex stainless steel having attractive combination of austenitic and ferritic properties is being used in industry such as petrochemical, pulp and paper mills. In this study, the corrosion and stress corrosion behavior of duplex stainless steel in 3.5% sodium chloride environment was investigated by weight loss measurements, electrochemical DC testing and slow strain rate test (SSRT). Weight loss data showed no significant corrosion after 1700 hours. Electrochemical polarization test in 3.5% NaCl solution exhibited a uniform corrosion rate of 0.008 mpy (calculated using Tafel analysis) showing passivity in the range of 735-950 mV. A comparison of the slow strain rate test in 3.5% NaCl solution with air shows almost a similar stress strain curve for duplex stainless steel. In comparison, the stress strain curves for 0.15% carbon steel show a loss of about 25% tensile elongation for the same comparison. The excellent corrosion and especially resistance to localized corrosion (pitting) is responsible for no loss of ductility in duplex stainless steel.

Updated CO2/H2S internal corrosion model of natural gas pipelines based on flow field calculations

The ‘A line’ of the Sichuan Natural Gas East Transportation in China was used as the subject of the study, and an existing CO2/H2S corrosion model was utilised to predict the uniform corrosion rate. Then, the flow parameters were simulated by computational fluid dynamics based on turbulence theory, and the influence on the corrosion rate of the pipeline was analysed in a detail to more accurately describe the corrosion problems of natural gas pipelines that contain CO2/H2S. After that, an updated CO2/H2S corrosion model under the influence of flow filed was proposed by modifying the existing CO2/H2S corrosion model. The actual condition was calculated by the updated CO2/H2S corrosion model. Results show that flow parameters, namely, velocity, turbulent kinetic energy and phase distribution, affect pipeline corrosion. The flow parameters did not change significantly at the small scale changes in the pipeline (5 and 15°) of a broad and smooth flow channel of the large diameter gas transport pipeline. The shape of corrosion often appears in the form of an elliptical sheet. The corrosion location and the corrosion rate calculated by the updated model are consistent with the wall thickness detection data in the site conditions, which verified that the updated CO2/H2S corrosion model is valid. The updated CO2/H2S corrosion model influenced by the flow field can predict the corrosion distribution and the corrosion rate of the three-dimensional key positions in natural gas pipelines.

A new method to predict the remaining life of corrosion casing for steam injection wells

As corrosion seriously reduces the service life of casing, considering no given formulas for remaining life calculation and the limitations of the laboratory tests and field data in investigating the lifetime of corrosion casing. To research the service ability of casing under uniform corrosion in steam injection wells, in this paper a new method is put forward, namely based on birth and death element technique (BDET), by building the thermo‐structural coupling model of casing‐cement‐formation to simulate the process of uniform corrosion. Three kinds of 5½, 7, and 9⅝ in. casing are studied to get the residual strength and remaining life under internal pressure, steam temperature and uniform corrosion rate to make comprehensive evaluation on the casing performance. The relation equations of the dimensionless residual strength with the dimensionless pressure and steam temperature are received based on the regression analysis. By comparison the prediction results with the field lifetime data, this method is proven to be reliable and applicative in predicting the lifetime of corrosive casing.

Performance Evaluation of Three Scale and Corrosion Inhibitors in Simulated Cooling Water in a Power Plant

Performance evaluation of three scale and corrosion inhibitors in simulated cooling water according to generating set in a power plant was presented in this paper. The scale and corrosion inhibition performance of the inhibitors were conducted by the methods of the static scale inhibition and rotary coupon tests respectively. The results indicated that 316L stainless steel has low uniform corrosion rate ranging from 0.0042 to 0.0048 mm/a in the simulated cooling water both with and without inhibitors. The drops of hardness in water with No.1 and No.3 inhibitors were slight, and these two inhibitors were of good scale inhibition while No.2 was poor. Keywords: simulated cooling water; scale inhibition; corrosion inhibition; performance evaluation; 316L stainless steel.

Corrosion Behaviors of 25CrMnVA Steel in CO<sub>2</sub> Flooding Enhanced Oil Recovery System

Influences of temperature and CO2 partial pressure on CO2 corrosion behaviors of 25CrMnVA steel were investigated in the simulated oil field environments. The corrosion rates were measured under high temperature and high pressure condition. SEM, EDS and XRD were used to analyze the morphologies and characteristics of corrosion scales on the steels. The results shows that the corrosion rates of 25CrMnVA steel change little below 65°C, the corrosion feature is uniform corrosion. The corrosion rates increase rapidly after 65°C, mesa corrosion is found on the surface of steel. The corrosion rates decrease firstly and increase subsequently with the rising of CO2 partial pressure, and the minimal corrosion rate presents near CO2 critical pressure. The compactness of corrosion scale improves with the increase of CO2 partial pressure below 8MPa, which causes uniform corrosion rate reduced. Under supercritical CO2 condition, the local defects in the surface of corrosion scale increase, and the compactness of corrosion scale reduces,which cause the increase of corrosion rate sharply. The corrosion rate and corrosion morphology are closely related to the state of corrosion scale.

Effect of Cl<sup>-</sup> Content, pH Value and CO<sub>2</sub> on Electrochemical Corrosion Features of Cr15 Super Martensitic Stainless Steel

The corrosion behavior of a Cr15 super martensitic stainless steel (Cr15 SMSS) was investigated in NaCl solutions by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Effects of Cl-content, pH value and saturated CO2on corrosion were sdudied. It was found that the parameters of maintaining passivity current density (ip), the critical pitting potential (Eb) and charge transfer resistance (Rt) of Cr15 SMSS varied widely under different conditions. The corrosion resistance of Cr15 SMSS decrease with increasing Cl-concentration and lowering pH value. BothipandEbincrease for Cr15 SMSS in CO2-saturated NaCl solution, which verified that the CO2in NaCl solution can result in lower pitting sensitivity and higher uniform corrosion rate to Cr15 SMSS.

Inhibitory activity of fluorine-containing quaternary ammonium salts comprising an N-methylpiperazinyl moiety

New fluorine-containing quaternary ammonium salts comprising an N-methylpiperazinyl moiety, which exhibited a high inhibiting capacity against hydrochloric acid corrosion of low-carbon steel, were synthesized. The polarization-resistance method was applied to determine the uniform corrosion rate of steel-3 in relation to the structure and concentration of the fluorine-containing substituents in the salts. It was found that the structure of the fluorine-containing moiety of the quaternary ammonium salts does not significantly influence the corrosion processes.

A mechanistic model for pipeline steel corrosion in supercritical CO2–SO2–O2–H2O environments

A mechanistic model was established to predict uniform corrosion rate and investigate the corrosion mechanisms of pipeline steel in supercritical CO2–SO2–O2–H2O environments. A six-region division (SIWDES: Supercritical CO2, Interface, Water film, Deposition, Electrodic, and Solid) was applied to mathematically describe the model. The modified three-characteristic-parameter correlation model was used to calculate the ion activity coefficients, which calculates the activity coefficients of ions in thin water film with high ionic strength. The model can reasonably predict the corrosion rate of pipeline steel for the primary variables, determine the concentration distribution of each component in the water and product films, and also reflect the impact of corrosion product film on corrosion rate. A comparative analysis between the model and the experimental results showed that the model reasonably predicted the effects of the main factors on corrosion rate.

Metal corrosion in geothermal brine environments of the Upper Rhine graben – Laboratory and on-site studies

Corrosion of construction materials in geothermal brine environments may play a major role in the long-term operation and stability of geothermal power plants. Herein the results obtained from laboratory and on-site experiments are compared in order to evaluate candidate materials as to their stability in hot brine environments. Weight-loss experiments in the Soultz-sous-Forêts (Upper Rhine graben, France) enhanced geothermal system, and electrochemical measurements in the laboratory were conducted using 8 metals (unalloyed steels, stainless steels, and Ni-based alloy). Weight loss and electrochemical measurements of the corrosion rate for unalloyed steels were found to be in good agreement.Both methods reveal unalloyed steels suffer surface recession with uniform corrosion rates <0.2mm/y, accompanied by surface deposits, providing minor protection. Stainless steel 1.4104 shows insufficient stability during 4-week exposure, whereas 1.4539 and 1.4404 do not exhibit any visible corrosion. However, electrochemical measurements on stainless steels result in pitting corrosion with pitting potentials defined for each steel quality. The very low corrosion rates obtained by electrochemical measurements for the Ni-based alloy 2.4856 were confirmed by on-site exposure tests.

Study on Corrosion Behavior of the 304 Stainless Steel in the Heavy Oil with High Salt, High Sulfur and High Acid Value

The uniform corrosion and localized corrosion of 304 stainless steel in heavy oil with high salt, high sulfur and high acid value were researched by weight loss method and electrochemical method. The corrosion morphology of samples with and without corrosion product films and the compositions of the corrosion product films were observed using SEM and EDS. The results show that the 304 stainless steel is inapplicable to the refinery equipment of this heavy oil because of the severe local corrosion even if the uniform corrosion rate is as low as 0.0107mm/a. The salt corrosion and sulfur corrosion occur on the local surface of 304 stainless steel because of the chloride ion formed by hydrolysis of salt in the small emulsifying water. The water soluble iron naphthenate produced by chemical reaction between naphthenic and ferrous sulfides impel the local corrosion of the 304 stainless steel.

EVALUATION OF GALVANIC CORROSION BEHAVIOR OF SA-508 LOW ALLOY STEEL AND TYPE 309L STAINLESS STEEL CLADDING OF REACTOR PRESSURE VESSEL UNDER SIMULATED PRIMARY WATER ENVIRONMENT

The article presented is concerned with an evaluation of the corrosion behavior of SA-508 low alloy steel (LAS) and Type 309L stainless steel (SS) cladding of a reactor pressure vessel under the simulated primary water chemistry of a pressurized water reactor (PWR). The uniform corrosion and galvanic corrosion rates of SA-508 LAS and Type 309L SS were measured in three different control conditions: power operation, shutdown, and power operation followed by shutdown. In all conditions, the dissimilar metal coupling of SA-508 LAS and Type 309L SS exhibited higher corrosion rates than the SA-508 base metal itself due to severe galvanic corrosion near the cladding interface, while the corrosion of Type 309L in the primary water environment was minimal. The galvanic corrosion rate of the SA-508 LAS and Type 309L SS couple measured under the simulated power operation condition was much lower than that measured in the simulated shutdown condition due to the formation of magnetite on the metal surface in a reducing environment. Based on the experimental results, the corrosion rate of SA-508 LAS clad with Type 309L SS was estimated as a function of operating cycle simulated for a typical PWR.

Corrosion of 16Mn Line Pipe Steel in a Simulated Soil Solution and the Implication on Its Long-Term Corrosion Behavior

In this work, corrosion of a 16Mn line pipe steel was investigated in a simulated soil solution by weight-loss test, electrochemical measurement, and surface analysis techniques. Moreover, the implication on the pipeline integrity was analyzed. It was found that a layer of corrosion product, i.e., ferrous and ferric oxides, would form on the steel surface to inhibit the further corrosion of the steel. The structure of the corrosion product layer would change with time, resulting in the steel corrosion experiencing a mechanistic alteration. The effects of oxygen and temperature on the steel corrosion were determined. Moreover, the uniform corrosion rate of the steel is within the acceptable range, and thus does not affect the pipeline integrity.

Enhanced bonded aircraft repair using nano-modified adhesives

The scope of the present work is to investigate if the introduction of a small weight fraction of multi wall carbon nanotubes (CNTs) in a polymer adhesive film can: (a) act as an effective corrosion barrier that inhibits access of the electrolyte to the surface of the aluminium substrate thereby preventing or notably delaying destructive localised aluminium corrosion, (b) lead to a hybrid system with galvanically compatible constituents and (c) enhance the adhesion of the film to the alloy substrate. Electrochemical measurements showed that the incorporation of CNTs into the epoxy film does not mediate the galvanic effect between substrate/coating, whilst it introduces limited localised degradation phenomena into the polymer matrix. However, it reduces the uniform corrosion rate of the film. Lap shear testing showed that the adhesion enhancement that stemmed from CNTs doping was significant in the absence of anodising of the substrate. It is proposed that a bi-layer patch, where the intermediate layer will be the neat polymer film and the over-layer will be the CNTs-reinforced film would be beneficial in terms of optimising the anodic protection by the patch and the galvanic compatibility of the alloy substrate/patch system.

&lt;i&gt;In Vitro&lt;/i&gt; Degradation of Ultrafine Grained Mg-Zn-Ca Alloy by High-Pressure Torsion in Simulated Body Fluid

In this paper the in vitro degradation of ultrafine grained (UFG) Mg-Zn-Ca alloy produced by HPT was investigated by electrochemical measurements and immersion tests in SBF. It was found that UFG Mg alloy had better degradation properties and also higher microhardness value than as-cast Mg alloy. The corrosion current density of UFG Mg alloy decreased by about two orders of magnitude, compared with that of as-cast alloy. Through electrochemical impedance spectroscopy (EIS) test，UFG Mg alloy showed a higher charge transfer resistance value. In immersion test, UFG Mg alloy in SBF exhibited more uniform corrosion and lower degradation rate (0.0763 mm/yr) than as-cast alloy. The degradation properties were related with the microstructure evolution, namely the grain refinement and redistribution of second phase. Keywords: Mg-Zn-Ca alloy; High-pressure torsion (HPT); Degradation behavior; Simulated body fluid (SBF); Microhardness

Impact of SO 2 concentration on the corrosion rate of X70 steel and iron in water-saturated supercritical CO 2 mixed with SO 2

The corrosion behavior of X70 steel and iron in water-saturated supercritical CO 2 mixed with SO 2 was investigated using weight-loss measurements. As a comparison, the instantaneous corrosion rate in the early stages for iron in the same corrosion environment was measured by resistance relaxation method. Surface analyzes using SEM/EDS, XRD and XPS were applied to study the morphology and chemical composition of the corroded sample surface. Weight-loss method results showed that the corrosion rate of X70 steel samples increased with SO 2 concentration, while the corrosion rate increased before decreasing with SO 2 concentration for iron sample. Comparing resistance relaxation method results with weight-loss method results, it is found that the instantaneous corrosion rate of iron is much higher than the uniform corrosion rate of the iron tablet specimens which are covered with thick corrosion product films after a long period of corrosion. The corrosion product films were mainly composed of FeSO 4 and FeSO 3 hydrates. The possible reaction mechanism under such environment was also analyzed, and the electrochemical reaction between the dissolved SO 2 in the condensed water film with iron is the critical reaction step.

Effect of mercury on corrosion in production wells in Gulf of Thailand

The effect of mercury on the corrosion of materials used for tubing in oil and gas production wells was studied. Carbon steel (L80) and 13% chromium stainless steel (13Cr) were selected for study by potentiodynamic polarisation. Simulated produced water, with the composition obtained from the Gulf of Thailand field, was used as a corrosive solution. Temperature kinetically increased the corrosion reaction. Chloride ions and carbon dioxide also enhanced the corrosion. Acidity increased the pitting corrosion of 13Cr and increased the corrosion rate of both 13Cr and L80. A concentration of 3–12 ppm of mercury lowered the current density in the passive region and increased the pitting potential of 13Cr. The corrosion rate of L80 was decreased with small amount of mercury addition. The 13Cr showed lower uniform corrosion rate than the L80 in all conditions of the simulated produced water.

Synthesis and inhibiting capacity of new fluorine-containing quaternary ammonium salts

New fluorine-containing quaternary ammonium salts exhibiting a high inhibiting capacity against hydrochloric acid corrosion of low-carbon steels were synthesized. The polarization resistance method was used to determine the uniform-corrosion rates of steel-3 and steel-35 in relation to the structure of fluorine-containing moieties of quaternary ammonium salts and their concentration.