Variation Of Corrosion Rate Research Articles

Variation of Corrosion Rate, Vcorr, during the Carbonation-Induced Corrosion Propagation Period in Reinforced Concrete Elements.

The structural systems of residential buildings in many developed countries have widely utilized reinforced concrete as the most common solution in construction systems since the early 20th century. The durability of reinforced concrete columns and beams is compromised, in most cases, by pathologies caused by the corrosion of their reinforcements. This study analyses the corrosion processes induced by carbonation in 25 buildings with reinforced concrete structures. The models estimate the service life of reinforced concrete elements by differentiating between the initiation period and the propagation period of damage, considering two possible stages: the time of corrosion propagation until the cracking of the concrete cover, and the time of propagation until a loss of section is considered unacceptable for structural safety. However, the mathematical expressions that model the propagation periods consider the same corrosion rate in both cases. This research has found that the average corrosion rate in elements with an unacceptable loss of reinforcement section was in the order of 8 times higher than the corrosion rate in cracked columns and beams without a loss of reinforcement. This opens up a path to improve the definition of the different stages experienced by a reinforced concrete element suffering corrosion of its reinforcements due to carbonation, because once the concrete has cracked, the corrosion rate increases significantly.

Insights into the effect of H2S on the corrosion behavior of N80 steel in supercritical CO2 environment

In this study, the corrosion behavior of N80 steel exposed to 80 bar supercritical CO2 and 0–15 bar H2S environments was investigated by weight loss test, surface analysis, water chemistry simulation, corrosion thermodynamic and kinetic calculations. The results show that a very low H2S pressure of 0.004 bar in supercritical CO2 environment boosts the corrosion rate of N80 steel, whereas the rate is considerably reduced with further increasing the H2S pressure. The variation of corrosion rate with H2S pressure largely depends on the changes in cathode process and overall protectiveness of corrosion product film caused by H2S. As the H2S pressure rises, the evolution of corrosion product film on the steel is as follows: FeCO3 dominated film below 0.16 bar H2S, FeCO3 and FeS mixed film within 0.16–4 bar H2S, and FeS dominated film over 4 bar H2S. Benefiting from the integrity of film structure and the uniformity of film composition, N80 steel experiences uniform corrosion in the formation environment of FeCO3 or FeS dominated film. However, the localized corrosion easily occurs in the formation environment of FeCO3 and FeS mixed film owing to the loss of film integrity induced by uneven precipitation of FeCO3 inside the corrosion product film.

Enhancement of mechanical properties and corrosion resistance of bainitic elastic rail clip (ERC) with finer microstructural morphology

Present work discusses the enhancement of hardness and tensile strength of the existing quenched and tempered elastic rail clip (ERC) by modifying the microstructure to bainite via austempering at 300ºC with various holding durations of 15 min, 30 min and 60 min after austenitization at 950ºC. Further, the corrosion resistance of these austempered ERC specimens evaluated in freely aerated 3.5 wt.% NaCl solution with the help of electrochemical tests (electrochemical impedance spectroscopy, linear polarization and potentiodynamic polarization) is better than the as-received (existing) ERC specimen with tempered martensitic structure. The variation in corrosion rate of the austempered ERC specimens is attributed to the finer galvanic couple formed between the ferrite and cementite phases in the bainitic structure. Further rust analysis using scanning electron microscopy and Raman spectroscopy after electrochemical tests shows the presence of various rust phases such as α-FeOOH, β-FeOOH, γ-FeOOH and α-Fe 2 O 3 . The higher protective ability index (α/γ*) as determined by the relative fraction of protective α-FeOOH and α-Fe 2 O 3 with dissolving β-FeOOH and γ-FeOOH phases of the austempered ERC specimen attributed further to their higher corrosion resistance. • Effect of asutempering on mechanical and corrosion behavior of elastic rail clip is studied. • Tensile strength of the austempered steel increases with increase of isothermal holding time. • Corrosion rate decreases with increase of bainite fraction in the austempered steel. • Rust constituents uniquely controls the corrosion of bainitic elastic rail clips. • High C at edge of RA near to bainitic ferrite results in higher dissolution of interface.

Effect of Small Amounts of Cr and Mo on Aqueous CO2 and H2S Corrosion of Low-Alloyed Steel

One of the important industrial issues is the corrosion of carbon and low-alloy steels exposed to a wet environment where CO2 and/or H2S are dissolved. In the case of carbon and low-alloy steels, mainly iron-based corrosion products such as iron carbonate and iron sulfides can form depending on the condition. Microalloys added in small amounts to carbon steel can change the water chemistry near the steel surface due to the dissolution of the microalloys, which may also alter the corrosion resistance of the steel and corrosion morphology. In this study, the individual microalloying effects of a small amount (1 mass%) of Cr and Mo added in carbon steel were investigated in a wet CO2 and H2S environment, where the formation of mackinawite (FeS) is considered to be the dominant iron-based corrosion product. The variation of corrosion rate and corrosion potential of the microalloyed steels was monitored in the NaCl solution aerated with CO2—10% H2S gas by linear polarization resistance measurements. The corrosion product formed on the steel surface was also analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy. The experimental results show that the addition of a small amount of Cr improves corrosion resistance by forming a dense film of FeS on the surface, while the addition of a small amount of Mo delays the formation of FeS on the surface and the corrosion resistance behavior is similar to that of steel with no additions.

Effect of grain size and volume fraction of eutectic structure on mechanical properties and corrosion behavior of as-cast Zn–Mg binary alloys

In this work, the effects of Mg content on the microstructure evolution, mechanical properties, and corrosion behavior of as-cast Zn-xMg (x = 0.1, 0.3, 0.5, 1.0, 1.5, and 3.0, wt.%) binary alloys were investigated. The microstructure of as-cast alloys is composed of α-Zn matrix and a ternary eutectic phase (α-Zn + Mg2Zn11+MgZn2). With the increase of Mg content, the average grain size of the alloys decreases from 104 μm to 11 μm while the volume fraction of eutectic structure increases from 3% to 84%, resulting in the improvement of tensile strength. In vitro immersion tests demonstrate that the corrosion rate decreases to a minimum value of 0.086 mm y−1 as Mg content increases from 0.1 to 0.3, followed by an increasing trend with the further increase of Mg content. The variation of corrosion rate with Mg content originates from the competition between the positive effect of grain refinement and the negative effective of eutectic volume fraction increment. Zn-0.3 Mg alloy has the optimal corrosion resistance because of the dominant role of grain refinement induced corrosion resistance enhancement. In addition, the corrosion mechanism varies from localized pitting to a more uniform corrosion as Mg content rises.

The electrochemical behavior of corrosion and passivation for Q235 carbon steel in acidic phosphate buffer solutions without and with NO2−

PurposeThe purpose of this paper is to reveal the mechanism of nitrite (NO2−) for the surface passivation of carbon steels in acidic environments through investigating the influences of 0.01 mol/L NaNO2addition on the corrosion and passivation behaviors of Q235 carbon steel in acidic phosphate buffer (APB) solutions (pH 2 to 6).Design/methodology/approachThe electrochemical techniques including open circle potential evolution, potentiodynamic polarization, electrochemical impedance spectroscopy and cyclic voltammetry were applied.FindingsIn APB solutions without NO2−, the Q235 steel presented the electrochemical behaviors of activation (A), activation-passivation-transpassivation and self-passivation-transpassivation at pH 2 to 4, pH 5 and pH 6, respectively; the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6.Originality/valueIn APB solutions without NO2−, the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6. With the addition of 0.01 mol/L NaNO2, into APB solutions, the variation of corrosion rate showed the same rule, but the surface passivation occurred over the whole acidic pH range, including the anodic passivation at pH 2 to 4 and the spontaneous passivation at pH 5 to 6.

Corrosion behavior of aluminum alloy 5754 in cement‐based matrix‐simulating nuclear waste disposal conditions

AbstractDepending on the lifetime and level of radioactivity of radioactive wastes, different disposal facilities are considered. Though low‐ and intermediate‐level short‐lived waste can be disposed in surface disposal facilities, deep geological disposal is considered for high‐ and intermediate‐level long‐lived waste. In France and Belgium, long‐term disposal is studied in clay host rock media. For aluminum, the disposal concept is based on encapsulation of the waste in a cement‐based matrix. It is also well‐known that aluminum is prone to severe corrosion in sufficiently alkaline environments leading to possible hydrogen production. To ensure the safety of the disposal facilities and the integrity of the cement capsules, the amount of aluminum that is disposed in each waste package must be specified and is limited to mitigate the level of hydrogen production by aluminum corrosion. In the present study, the corrosion resistance of an aluminum alloy (grade EN‐AW‐5754/H111) in two different cement matrices was studied in different configurations at room temperature. In each case, the evolution of hydrogen production was monitored to address the corrosion rate variation versus time.

Assessment of Corrosion of Mild Steel Buried In Soils of the Niger Delta, Nigeria

This study determines the corrosion rate and percent weight loss of mild steel buried in soils of the Niger Delta Area of Nigeria. Six geologic zones representing the upland and wetland soils were used for the assessment. The corrosion rates of mild steel in these soils were monitored to assess the extent of corrosion. However, the upland soils (Odagwa, Ogoni, Ahoada and Omoku) were more resistant to corrosion than the wetland (Kaiama and Elebele) soils. The corrosion rate of mild steel at the 24th month was in the following order of corrosivity: Elebele > Kaiama > Omoku > Ahoada > Ogoni > Odagwa. The percent weight loss was higher at the 24th month, with the highest values found at the Meander Belt Deposits of Elebele. Alternately, the Coastal Plain Sands were found to have the least percent weight loss with the lowest value recorded at Odagwa site at the 24th month. The percent weight loss at the 24th month is in the following order: Elebele > Omoku > Kaiama > Ahoada > Ogoni > Odagwa. The variation in corrosion rate and weight loss of mild steel buried in the different soil types is caused by the aquic moisture regime of the soils, anthropogenic activities carried out, microorganisms present in the soils, and also, the physico-chemical properties of the soils.

An experimental and numerical investigation of CO2 corrosion in a rapid expansion pipe geometry

A combined experimental and numerical methodology for accurately translating Rotating Cylinder Electrode (RCE) CO2 corrosion data to complex pipe flow geometries is presented. Computational Fluid Dynamics (CFD) simulations are used to determine the local variation in mass-transfer coefficient throughout a rapid expansion (as an example geometry). An empirical correlation between mass-transfer coefficient and corrosion rate derived from RCE experiments is then integrated into the CFD model to predict the variation in corrosion rate throughout the fitting. Electrochemical and mass loss corrosion experiments using carbon steel coupons integrated into a 3D printed rapid expansion within a flow loop validate the approach.

Evaluation of DC-Subway Stray Current Corrosion With Integrated Multi-Physical Modeling and Electrochemical Analysis

Leakage of stray current can cause serious problems by accelerating the corrosion process of a buried pipeline in the subway. A multi-physical finite element model of the DC-subway traction system was established in this study, and the dynamic process of the stray current corrosion on buried pipeline was calculated according to the real time traction conditions. In this study, the corrosion rate variation of stray current is evaluated, and the corrosion trend of stray current is quantitatively calculated. The model simulation shows that the stray current corrosion is significantly higher than other processes during the acceleration process of the subway locomotive. And the potential of the buried pipeline reaches a maximum value when an up-rush of traction current occurs. The corrosion is mainly concentrated in the anode region of the buried pipeline, and the closer the buried pipeline is to the rail the more serious the corrosion is. A corrosion experiment of N20 carbon steel was carried out and verified by finite element model. The results further show that the finite element model can quantitatively calculate and predict the mass loss of buried metal caused by stray current corrosion.

An experiment study on corrosion rate variation of low welded carbon steel in a different solution

The corrosion reaction of low carbon steel alloy welded with different shape(V &X) method is investigated after relives stress by tempering at (600°C,) for (30)minute then specimens divided in three groups, first normalizing, the second group annealing, third group Quenching, all groups heated to(750°C,)then cooling with still air, in the furnace &water according to its heat treatment sort then immersed in three kind solution, acidic solution (0.5M HCl) basic(NaCl) & distal water for one month each (7days) take the weight to compute rate of corrosion in welded zone as weight loss.

Corrosion Behavior of Q235 Steel Exposed in Deepwater of South China Sea

For the first time, the corrosion behavior of Q235 steel in 1200, 2000 and 3000 m deepwater of South China Sea for 0.5 year was reported in this study. The corrosion morphology and corrosion products properties were investigated using different techniques, such as 3D optical microscope, scanning electron microscope, x-ray diffraction analyzer and electrochemical impedance spectroscopy. The main environmental factors influencing the corrosion rate of Q235 in deep sea were discussed by applying gray relational analysis. The results indicated that uniform thinning occurred after exposure. A large number of tiny pits were distributed under the corrosion products with a two-layer structure. The corrosion rate and average pitting depth of samples exposed at 2000 m were lower than those exposed at 1200 and 3000 m, and the main environmental factors determining the variation of corrosion rate at different depths were temperature and dissolved oxygen concentration. Hydrostatic pressure had slight effect on the corrosion rate of Q235 steel, but promoted the formation of a more uniform corrosion morphology.

Corrosion of Q235 carbon steel influenced by the introduction of aerogenic and aerobic bacteria

Corrosion of carbon steel is investigated in the presence of Synechococcus sp. (S. sp., an aerogenic strain) with or without the coexistence of Pseudoalteromonas sp. (P. sp., an aerobic strain). Results of electrochemical and weight loss measurements suggest that the corrosion of carbon steel is continuous in S. sp. containing media while it is inhibited initially and accelerated finally in the coexistence of S. sp. and P. sp. This variation in corrosion rate is believed to be closely related to the difference in the growth and metabolism of two strains in different media. In media containing S. sp. alone, the slow reproduction of S. sp. leads to the relatively stable dissolved oxygen (DO) concentration and the continuous corrosion. In the case of S. sp. + P. sp., P. sp. consume DO and form protective biofilm at the initial stage, and then the death of P. sp. and the rapid reproduction of S. sp. cause the increase of DO concentration and the formation of porous corrosion products, leading to the change of corrosion rate.

A new approach to determine the chloride threshold initiating corrosion: Preliminary results

The initiation of corrosion by chlorides is traditionally based on the existence of a threshold that would lead to corrosion. Almost all existing approaches considered implicitly that corrosion induced by chlorides is uniform and take not into account the intrinsic localized character of corrosion in reinforced concrete structures. This work aims to implement a new test protocol that takes explicitly into account the localized nature of chlorides-induced corrosion by inducing physical separation between anode and cathode thus permitting to measure the corrosion current. The anodic part allows to test different levels of chlorides and the cathodic part to highlight the ohmic (limiting ionic current by low porosity) and cathodic (restricting access to oxygen due to saturation of porosity, low porosity, dioxygen consumption by additions) control of corrosion. The chloride threshold is set on the basis of a threshold corrosion current that is considered acceptable with respect to the structure’s life. The first results provide a preliminary idea of the variation of corrosion rate in function of chlorides content. This method also highlights the influence of surface condition of the steel-concrete interface on the corrosion current.

Effect of Environmental Pollution on Corrosion Characteristics of 3003 Aluminium Alloy Exposed in Different Parts of India

Corrosion behaviour of 3003 grade of aluminum alloy is investigated by exposing its samples under different climatic and pollution zones of India namely Jamshedpur, New Delhi, Lucknow, Mumbai, Nagpur, Kolkata, Chennai and Palampur. Results indicate that pollutants in the atmosphere, especially PM10, considerably affect the corrosion rate. Electrochemical impedance spectroscopy and direct current anodic polarization studies indicate the formation of very protective film on specimens exposed to cleaner environments. Raman spectroscopy and XRD studies of the passive films formed on exposed samples help to explain the variation in corrosion rate of the metal in different climatic conditions. The deposition of fine particulates on the exposed surface of the samples are observed to act as a reservoir of corroding species by absorbing corrosive gases, moisture and anion and cation species resulting in the formation of corrosion cells. The mechanism for the breakdown of passive film resulting in accelerated rate of corrosion of the alloy exposed to polluted environments is discussed.

In-Situ Corrosion Monitoring of Iron and Zinc in Atmospheric Environments

Traditionally, for evaluating corrosion resistance of materials used in atmospheric conditions, exposure tests in the actual environment and accelerated corrosion tests in the laboratory have been widely used. Till now, it has been very difficult to estimate in detail corrosion rate variations caused by the change of each environmental factor such as temperature, relative humidity, amount of airborne sea salt during the test periods. Also, it requires a long time period to evaluate the corrosivity in actual corrosive atmospheric environments. For these reasons, an in-situ corrosion monitoring technique is useful. Time variation of corrosion rate has been successfully monitored by using an electrical resistance corrosion sensor, which converts the increase of electrical resistance caused by metal consumption to corrosion loss. Additionally, a new accelerated corrosion test was authorized as ISO 16539 Method B on March 1, 2013. This test has good correlation with corrosion behavior in an actual corrosive atmospheric environment. In this study, the details of the corrosion rate of steel and zinc were evaluated by the accelerated corrosion test (ISO 16539 Method B) and atmospheric exposure test. In addition, the relation between corrosion rate and each environmental factor was analyzed. Two kinds of electrical resistance corrosion sensors, an Fe sensor (250 µm thick) and a Zn sensor (50 µm thick), were used. In the accelerated corrosion test (ISO16539-Method B), the corrosion depth as evaluated by the sensors displayed a good correlation with that of the exposure test samples. The variation in the corrosion rate could be evaluated by the sensors. And also, it was confirmed that the corrosion rate increased during the wet stage and decreased during the dry stage in both sensors. In exposure tests in Okinawa and Kawasaki, the variation of the corrosion rate due to the effects of changeable environmental conditions throughout the year could be evaluated by the sensors. Okinawa is seashore area at the s southern island in Japan, and Kawasaki is industrial area in Japan. The corrosion rate in Okinawa as evaluated by the Fe sensor was greater than that found in Kawasaki. However, the corrosion rate in Okinawa as evaluated by the Zn sensor was almost the same as that in Kawasaki. The corrosion sensors could clarify the difference in corrosion behavior between steel and zinc. Furthermore, the relationship between the corrosion rate and the environmental factors (temperature, relative humidity, amount of airborne sea salt, etc.) was analyzed. The corrosion rate of steel had a positive relation with temperature, relative humidity and airborne sea salt. The dependence of corrosion rate of zinc on environmental factors was also investigated. Comparison of corrosion behavior and its dependence of environmental factors between iron and zinc will be discussed.

Corrosion rate variation of SS 316 under simultaneous factors considering turbulence effect

Investigation of corrosion rate under the simultaneous effect of parameters is a new and important approach that makes our experimental media closer to real condition and offers more realistic results. In this study, the effect of some important marine factors including temperature, pH, velocity and salinity on the corrosion rate of SS 316 is considered synergistically using two by two graphical curves. Experiments are performed in turbulence condition, and each parameter is applied at three levels. The results of this research are compared with the achievements of a former synergistic study of parameters, which had calculated the contribution percentage and qualitative influence of marine factors in laminar condition. This research presents the critical points in the change of corrosion rate under the synergistic effect of parameters and compares the capability of factors in changing the rate of corrosion and studies their qualitative effect.

Studies on the effect of Zn ions on the corrosion behavior of iron-base alloys relevant to desalination and power plant conditions

The corrosion behavior of mild steel and AISI 304L SS in the presence of dissolved Zn ions under different experimental conditions have been investigated. Experimental conditions include: variation in aqueous medium, Zn ions concentration, pH, dissolved oxygen, and flow condition. The variation in corrosion rate in the presence of varying concentrations of Zn ions was determined using weight loss technique and spectrophotometric analysis of iron ions entered into the test solutions after completion of immersion. The pH of the test solutions was also monitored during the entire period of immersion. The Zn ions present in the test solutions after completion of immersion were estimated using atomic absorption spectrophotometer (AAS). Open circuit potential (OCP) measurements and potentiodynamic polarization (PDP) measurements were carried out to find out the role of Zn ions on the corrosion behavior of mild steel and SS 304L. The surface morphology of steel before and after immersion in aqueous solution containing Zn ions was also examined using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The influence of Zn ions on the corrosion behavior of mild steel is quite pronounced and show interesting trends whereas SS 304L is unaffected both in distilled water or artificial seawater.

Simultaneous Investigation of Marine Factors Effect on Corrosion Rate of SS 304 in Turbulent Condition

Seawater is generally considered to be the most corrosive of the natural environments which threatens all the steel structures in their life time. The effect of environmental marine factors is extremely important in its corrosive behaviour. In this article, the influence of different marine parameters including pH, temperature, salinity and velocity is evaluated on the corrosion rate of SS 304 samples under turbulent condition. Since in actual marine environment, the entire parameters act simultaneously and as there is the possibility of differences between individual and synergistic influences of effecting factors, the influence of each considered parameter on the rate of corrosion has been studied under the combined effect of other factors. Finally, the results are presented via the graphs of dual factor effects which illustrate two-by-two influences of environmental parameters on corrosion rate variation. This research presents the difference between the qualitative and quantitative effects of a parameter under different ranges of considered parameter and also under the simultaneous effect of other combined acting factors, which emphasizes the importance of synergistic effects. In each case, the results obtained in turbulent condition are compared with previous study which had investigated the effect of marine parameters in laminar medium.

Grain character influences on corrosion of ECAPed pure magnesium

This study seeks to clarify the influence of grain character on the corrosion rate of Mg. There is a special need to understand the largely unknown corrosion–grain size relationship for Mg, which nominally displays poor corrosion resistance, since any efforts to reduce or control the rate of Mg corrosion are of large technological significance. In this work, the microstructure is modified by equal channel angular pressing (ECAP) with up to eight passes, to achieve a range of refined microstructures ranging in grain size from a few hundred micrometres to a few micrometres. Results reveal a significant variation in corrosion rate with the number of ECAP passes, and hence grain size, which is of key significance. The results are discussed in terms of grain size, misorientation, along with resultant surface state produced and electrochemical/polarisation signatures collected.