Corrosion Rate Of Carbon Steel Research Articles

The effect of different heavy metals pollutants in refinery effluent on corrosion rate of carbon steel

The presence of heavy metal pollutants in refinery effluent significantly impacts the corrosion rate of carbon steel. The focus of this research is to analyze the impact of various inorganic pollutants, including copper, vanadium, nickel, and chromium ions, on the corrosion of carbon steel across different solutions. After conducting a thorough examination of various operating conditions, including pollutant concentration (ranging from 300-3000 ppm), temperature (30-60? C), and flow velocity (0-800 rpm). Our research shows that copper ions have the highest corrosion rate, with vanadium ions being a close second. Conversely, nickel and chromium had the most negligible impact on corrosion rate and, in some instances, even exhibited corrosion inhibition effects. It was also observed that an increase in flow velocity and temperature significantly amplified the corrosion rate of the metal ions investigated.

Effect of seawater flow velocity in South Malang on the corrosion rate of low carbon steel with a corrosion coupon rack

Corrosion is a phenomenon of damage to metal that can be influenced by several factors, including environmental factors, namely pH, humidity, temperature, and impurity factors. Corrosion that occurs due to the flow of a fluid is known as erosion corrosion. One type of metal that is susceptible to corrosion is carbon steel. Carbon steel material is very commonly used in the industrial world. An application of carbon steel is in piping systems that transport fluids; thus, fluid flow velocity affects the corrosion resistance of carbon steel. This research aimed to determine the effect of seawater flow on the corrosion rate of low carbon steel (ST 37) with variations in seawater velocity. This research is a type of laboratory-scale experimental research using coupon rack corrosion test equipment. The variations in seawater velocity used are 0 L/min, 15 L/min, 20 L/min, and 25 L/min. Observations of each experiment were carried out every 6 and 12 hours. The corrosion rate was analyzed using the weight loss method, namely by calculating the initial and final weight of the specimen before and after the experiment. The results show that increasing seawater flow velocity also increases the corrosion rate on steel specimens, with the lowest corrosion rate at 10.262 mpy on specimens with a variation of 0 L/min, while the highest corrosion rate is 48.743 mpy on specimens with a variation of 25 L/min. It can be concluded that the velocity of the fluid flow and the type of particles contained in the flow affect the rate of erosion-corrosion. The higher the fluid flow velocity and the more abrasive the particles contained in the flow, the faster the rate of erosion-corrosion.

Effect of tetrakis(hydroxymethyl)phosphonium sulfate (THPS) on the microbial community and corrosion of carbon steel in a simulated crude-oil storage tank environment

The biocorrosion process has been a problem for the oil and gas industry, involving deterioration of facilities, loss of oil quality, metal loss, and oil leaks. In oil storage tanks, the presence of a metallic surface along with crude oil and water poses a biocorrosion risk. Biocides are used to control the biocorrosion of different metallic infrastructures, tetrakis(hydroxymethyl)phosphonium sulfate (THPS) is commonly used due to its low environmental impact and its effectiveness in preventing sulfate-reducing bacteria (SRB) growth. The treatment effect with one THPS application on microbial community and corrosion rates was evaluated in a batch fractionated assay containing water from a crude oil storage tank, carbon steel coupons and crude oil. The effects of the treatment were monitored for 60 days. The number of planktonic bacteria and archaea estimated by qPCR decreased at the beginning of the treatment with THPS, however, 60 days after the application their number was higher, as were the sulfate-reducing microorganisms (SRM) and methanogens (MA). The diversity analysis of the 16S rRNA gene showed that the relative abundance of the genus Desulfovibrio and Methanocalculus was higher on day 8 in the presence of THPS, but by day 60 there were no differences. The biocide did not inhibit bacterial and archaeal biofilm attached to the SAE 1010 carbon steel coupons and produced a decrease in corrosion rates by blocking the surface. The proximity of the corrosion potential to the pitting potential indicated a high susceptibility to localized corrosion. The results suggested that the changes in the microbial community by THPS treatment were related to the corrosion rates of carbon steel, rather than the number of microorganisms attached to the coupon.

Inhibition of Acid Descaling and Pickling Effects on API 5CT Carbon Steel Using Schiff Base Ligand (C24H21N5O2) in 1 M H2SO4 Solution

The objective of this paper was to investigate the inhibition of acid descaling and pickling effects on API 5CT carbon steel using Schiff base ligand (C24H21N5O2) in 1 M H2SO4 solution using Potentiodynamic Polarization (PDP), Electrochemical Impedance Spectroscopy (EIS) and Weight Loss (WL) techniques. FTIR spectroscopy shows that there was a strong adsorption of SFBL on the carbon steel surface due to formation of a complex surface film. Corrosion rate of carbon steel decreased exceedingly from 0.0155 to 0.0002 while inhibition efficiency of SFBL rose from 78.8 % to 98.9 % between 20 ppm and 100 ppm respectively. PDP measurements revealed a mixed type inhibitor. EIS measurement reveals that the increasing charge transfer resistance was directly proportional to the increase inhibitor concentration and the double layer capacitance dropped from 1.98 to 0.61 indicating a stronger inhibition.

Effect of Adsorption and Interactions of New Triazole-Thione-Schiff Bases on the Corrosion Rate of Carbon Steel in 1 M HCl Solution: Theoretical and Experimental Evaluation.

Due to the unique properties of steel, including its hardness, durability, and superconductivity, which make it an essential material in many industries, it lacks corrosion resistance. Herewith, two novel triazole-thione Schiff bases, namely, (E)-5-methyl-4-((thiophen-2-ylmethylene)amino)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TMAT) and (E)-4-(((5-(dimethylamino)thiophen-2-yl)methylene)amino)-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (DMTMAT), were synthesized and characterized. The corrosion inhibition (CI) ability of these two molecules on carbon steel in an aqueous solution of 1 M HCl as well as their interaction with its surface was studied using a number of different techniques. The results confirmed that the CI capability of these organic molecules depends on their strong adsorption on the metal surface and the formation of a protective anticorrosion film. Weight loss tests revealed that the inhibition efficiencies of TMAT and DMTMAT were 91.1 and 94.0%, respectively, at 1 × 10-3 M concentrations. The results of electrochemical impedance spectroscopy (EIS) indicated that there was a direct relationship between the inhibitor concentration and the transfer resistance. Potentiodynamic polarization (PDP) experiments have proven to be mixed-type inhibitors of C-steel in aqueous hydrochloric acid solution and follow the Langmuir adsorption isotherm model. Several thermodynamic and kinetic parameters were calculated. The negative values of the adsorption-free energy are -36.7 and -38.5 kJ/mol for TMAT and DMTMAT, respectively, confirming the spontaneity of the adsorption process. The MD simulation study's findings show that the inhibitor molecules are nearly parallel to the metal surface. The interaction energy calculated by the MD simulation and the inhibitory trend are the same. The practical implementation is consistent with what the computer models predicted.

MICROSTRUCTURE AND EROSION CORROSION PROPERTY OF CRNI ALLOYED COATING ON CARBON STEEL

In this study, CrNi alloyed coating was deposited on Q235 low carbon steel by arc-added glow plasma depositing technique in order to increase the corrosion resistance property. It was found that the CrNi alloyed coating was composed of face-centered cubic Cr0.7Ni2.9Fe0.36 phase. The EDS results indicated that 7.3 [Formula: see text] m coatings were prepared which was bonded metallurgically with the substrate. The salt spray corrosion test result showed that the corrosion product film of coating was dense while the corrosion film of carbon steel was multilayered in morphology. The corrosion product film of CrNi coating reduced the corrosion rate. However, the corrosion product of Q235 with loose multi-layer structure increased corrosion process. The erosion corrosion properties of carbon steel and coating were tested in NaCl solution with different flowing speed through electrochemical test methods. The erosion corrosion results showed that the corrosion rate of carbon steel was increased in flowing NaCl solution. The corrosion product of CrNi coating could protect inner material in NaCl solution at flowing speed of 2 m⋅s[Formula: see text] to 6 m⋅s[Formula: see text].

Effect of turbulent flow on the oxide properties of carbon steel in alkaline water

The purpose of this study is to investigate the changes in the morphology, chemical state, defect density, and impedance of oxides formed on SA 106 Gr.B carbon steel by turbulent water flow at the micro and atomic levels. A compact magnetite layer composed of multi-faceted particles is formed in stagnant water, while a porous magnetite layer composed of particles without a certain shape is formed in turbulent water. Ferrous ions are preferentially dissolved from the oxide in turbulent water, which increases the vacancies in the oxide lattice. An increase in the concentration of point defects is shown to be comparable to an increase in the corrosion rate of carbon steel. The flow-accelerated corrosion behavior is also well correlated with the electrochemical impedance parameters including the charge transfer resistance and capacitance. Our study provides a further understanding of carbon steel corrosion under turbulent water flow conditions.

Synergistic inhibitive effect of a hybrid zinc oxide-benzalkonium chloride composite on the corrosion of carbon steel in a sulfuric acidic solution

Abstract Zinc oxide and quaternary ammonium-type surfactants have been separately recognized for their anti-corrosive efficiencies. Their composite, not investigated so far, could provide a synergetic anti-corrosion effect. In this respect, the aim of this study is to synthesize a composite material consisting of zinc oxide and benzalkonium chloride (ZnO-BAC) in varying mass ratios (3:1, 1:1, and 1:3). The inhibitory properties of the ZnO-BAC composite against carbon steel corrosion in a 0.5 M sulfuric acid solution were assessed under ambient conditions. First, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to examine the chemical structure of the prepared composite. Then, the corrosion inhibitive performance of the devised inhibitors was screened using electrochemical, hydrogen collection, and weight loss measurements. Further, the surface morphology was examined using a scanning electron microscope, both before and after immersion in the corrosion medium. The electrochemical measurements indicate that the prepared inhibitor exhibits a predominant cathodic inhibition behavior and the maximum inhibition efficiency, approximately 91.9%, was achieved for one-to-one mass ratio. Similar results were obtained from weight loss and hydrogen evolution measurements, which showed that the ZnO-BAC composite reduced the corrosion rate of carbon steel by 69.9% and 64.9%, respectively. Finally, molecular dynamics and an adsorption equilibrium model were used to elucidate the mechanism of corrosion inhibition by the ZnO-BAC composite, which exhibits a high adsorption energy on the iron surface.

Monitoring Atmospheric Corrosion of Carbon Steel Under Controlled Electrolyte Droplet Distributions

Field exposure testing and accelerated corrosion testing are two common approaches applied in the industry to assess the atmospheric corrosion rate of a specific material, both relying on visual inspection and weight change of the specimen. Field exposure testing occurs under natural atmospheric conditions but requires exposure times spanning decades, whereas accelerated corrosion testing shortens the exposure time to weeks; however, the connection between the natural environment and accelerated corrosion chamber conditions remains unresolved. Efforts have been made to correlate accelerated corrosion results with those obtained in field exposure based on weight loss, both qualitatively and quantitatively, primarily empirically and limited to small datasets.This work examines the link between modified field exposure testing and the environment from the electrolyte perspective, under controlled laboratory conditions. In-situ monitoring and analysis of corrosion rate, electrolyte condition, and environment are demonstrated to be feasible, and the effect of NaCl concentration and droplet distribution on the atmospheric corrosion rate of carbon steel has been addressed.This work proposes a setup wherein multiple droplet-based conditions are created, and corrosion kinetics are actively monitored using the electrical resistance method. The sample surface is simultaneously monitored with an optical microscope, through which both droplet distribution evolution and corrosion product formation can be visualized.

The Performance of Papaya Leaf Extract on The Corrosion Rate of Carbon Steel in 0.5 M HCl Solution

The performance of papaya leaf extract as a corrosion inhibitor for carbon steel metal in 0,5 M HCl solution was investigated using immersion methods. The measurements were conducted in different concentrations of papaya leaf extract and immersion time. It also investigated the effect of temperature on the corrosion rate of carbon steel without and with the use of papaya leaf extract. It would enhance the corrosion inhibitor regarding these materials since the study is still rarely elaborated. The experiments were conducted using ASTM G-31-72 standard practice for laboratory immersion corrosion testing. The carbon steel corrosion rate and inhibition efficiency were examined. Results show that the concentration of papaya leaf extracts influences the corrosion rate of carbon steel. Higher papaya leaf extract concentration reduces the carbon steel corrosion rate. The increasing immersion time increases the corrosion rate. Moreover, increasing temperatures increase the corrosion rate. The inhibition efficiency increases with the increase of papaya leaf extract concentration. The highest inhibition efficiency is 73.10% which reached a concentration of 5% and immersion times of 5 days.

PEMETAAN KOROSIFITAS ATMOSFER MENGGUNAKAN LOGAM BAJA KARBON RENDAH DAN KARBON TINGGI PADA WILAYAH KOTA SURABAYA

Corrosion of metals is inevitable. One of the factors that affect corrosion is environmental conditions that contain pollutants like SO2, NO2, and Cl- which are found in many industrial and seaside areas. Surabaya is an area that has 2 types of conditions. In addition, Surabaya is the capital of the province where infrastructure development is running rapidly. Thus, this study maps the level of atmospheric corrosion in five areas in Surabaya by collecting corrosion rate data for 4 months with weight loss method using AISI 1020 Steel and SK5 Steel as test metals. XRD and SEM-EDX tests were conducted to compare the corrosion results. The average corrosion rate of low carbon steel was 0,6561 mpy and high carbon steel was 1,2523 mpy. The results concluded that the high level of atmospheric corrosivity of low carbon steel is in Sukomanunggal, Bulak, Rungkut, Pakal, Krembangan, and Bubutan sub-districts. The medium level is in Tegalsari, Gubeng, Tenggilis Mejoyo, Karang Pilang, Jambangan, Sawahan, and Dukuh Pakis sub-districts. The low level is in Lakarsantri, Mulyorejo, Simokerto, Sambikerep, Genteng, and Wonokromo sub-districts. Meanwhile, high atmospheric corrosivity levels for high carbon steel are in Krembangan, Karang Pilang, Bulak, Tenggilis Mejoyo, Pakal, and Jambangan sub-districts. The medium level is in Rungkut, Sawahan, Bubutan, Wonokromo, Tegalsari, Sukomanunggal, and Lakarsantri sub-districts. The level is in Dukuh Pakis, Genteng, Gubeng, Simokerto, Sambikerep, and Mulyorejo sub-districts. This mapping is based on the level of corrosion in each sub-district which is influenced by the presence of industry and its geographical location.

Novel synthesized triazole derivatives as effective corrosion inhibitors for carbon steel in 1M HCl solution: experimental and computational studies

This article outlines the synthesis of two derivatives of 4-amino-5-hydrazineyl-4H-1,2,4-triazole-3-thiol for the prevention of carbon steel corrosion in 1M HCl solution. These derivatives are (Z)-3-(1-(2-(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)hydrazono)ethyl)-2H-chromen-2-one (TZ1) and 5-(2-(9H-fluoren-9-ylidene)hydrazineyl)-4-amino-4H-1,2,4-triazole-3-thiol (TZ2). Weight loss, electrochemical experiments, surface examinations, and theoretical computation are used to evaluate the effectiveness of the two compounds to be used as corrosion inhibitors. Weight loss and electrochemical studies demonstrate that these derivatives reduce the corrosion rate of carbon steel. To examine the morphology and constitution of the carbon steel surface submerged in HCl solution as well as after adding inhibitors, surface examination tests are performed. Analysis of the test solution via UV–visible spectroscopy is employed to check the possibility of complex formation between inhibitor molecules and Fe2+ ions released during the corrosion process. In order to explore their biological activity, the antibacterial activity was investigated against (E. coli and Bacillus subtilis). Finally, theoretical confirmation of the experimental findings is provided by quantum chemical (DFT) and Monte Carlo (MC) simulation studies. More adsorption sites are present in the derivatives of 4-amino-5-hydrazineyl-4H-1,2,4-triazole-3-thiol, which offer a novel perspective for developing new classes of corrosion inhibitors with substantial protective efficacy, especially at high temperatures.

Corrosion behavior and mechanism of carbon steel in industrial circulating cooling water system operated by electrochemical descaling technology

Electrochemical descaling technology (EDT) can significantly increase the concentration ratio of industrial circulating cooling water systems (CCWSs), thereby reducing water, capital, and energy consumption. However, our understanding of the impact of EDT on carbon steel corrosion in CCWSs is limited, which increases the risk of long-term operation. In this study, the influence of the EDT on the corrosion characteristics of carbon steel was comprehensively investigated in field CCWSs (E-CCWSs) and compared with a system using traditional chemical processes (C-CCWSs). The corrosion characteristics, corrosion products, and corrosion mechanism of carbon steel have been studied using various testing methods, including the weight loss method, electrochemical testing, Confocal Laser Scanning Microscopy (CLSM), Advanced Mineral Identification and Characterization System (AMICS), etc. The research showed that the corrosion behavior of carbon steel in a circulating water system was similar and could be divided into three stages: the initial stage (corrosion rate increased), middle stage (corrosion rate slowed down gradually), and later stage (corrosion rate was stable). Owing to the lack of the corrosion inhibitor film, the corrosion rate of carbon steel in the electrochemical circulating water system was faster in the initial stage. However, the rapidly thickened corrosion product layer had a protective effect on the carbon steel. The corrosion of carbon steel entered the middle and late stages faster, and the corrosion rate decreased rapidly and tended to stabilize. In the long term, the corrosion rate of carbon steel in the electrochemical system was slightly lower than that in the chemical system. E-CCWS encounter serious pitting problems. At 120 days, the pitting depth in electrochemical systems was 108.22 μm, almost twice as deep as that in chemicals (54.79 μm). This research has important reference value for corrosion prevention and risk assessment of EDT for practical applications.

Electrochemical investigation on localised corrosion under silica sand deposit layers of carbon steel within a bespoke test cell

The corrosion behaviour of deep pit-like features on carbon steel under silica sand deposits has been evaluated using a bespoke localised corrosion cell. Local pH and electrochemical measurements were performed, including impedance spectroscopy and galvanic coupling. The corrosion rate of X65 carbon steel at four different recession depths up to 9 mm was evaluated in the presence and absence of a ∼8 mm-thick silica dioxide deposit layer, in a carbon dioxide-saturated environment. The deposit reduced corrosion rates to approximately 1 mm·yr−1 and iron carbonate formed on the steel surface under the deposit due to an increase in local pH.

Study on corrosion behavior of typical carbon steel and low alloy steel in deep sea of different sea areas

Abstract In order to meet the development needs of deep-sea oil and gas resources, deep-sea corrosion coupon tests were carried out in the South China Sea, the Western Pacific Ocean, and the Indian Ocean, which can provide a strong guarantee for the rationality of material selection of oil and gas pipelines, platforms and other facilities. In-depth studies were conducted on the environmental adaptability of typical carbon steel and low alloy steel materials after exposure for one year in the deep-sea environment of different sea areas. The main environmental factors affecting deep-sea corrosion behavior were also collected and analyzed. The results showed that the corrosion morphology of carbon steel and low alloy steel in deep sea environment was more uniform than that in the shallow seawater. With the increase of seawater depth, the evolution law of their corrosion rates in different sea areas was similar, with an obvious decline of corrosion rate in the beginning. The gray correlation results indicated that it was mainly controlled by temperature and dissolved oxygen. The high hydrostatic pressure had limited effect on accelerating the deep sea corrosion rate of carbon steel and low alloy steel, but it promoted the formation of more uniform corrosion morphology.

Dried Clove Leaf as Corrosion Inhibitor for Medium Carbon Steel in Acidic Media

Medium carbon steel is a widely used steel variant known for its susceptibility to mechanical property degradation due to corrosion. In order to decrease the corrosion rate of medium carbon steel, various protective measures are employed such as the addition of inhibitors. Dried Clove Leaf (DCL) extract was extracted and applied as an inhibitor for medium carbon steel AISI 1040 in different acidic environments. Fourier-transform infrared spectroscopy (FTIR) was conducted to analyze the compounds present in the clove leaf extract. Subsequently, corrosion rate and inhibitor efficiency were assessed to demonstrate the effectiveness of the clove leaf inhibitor. The parameters under this research included varying inhibitor concentrations for 0%, 5%, 10%, 15%, and acidic media using HCl and H2SO4. The successful extraction of DCL was confirmed by the presence of a C=C bond in the FTIR results, occurring at wavenumbers ranging from 1638 to 1514 cm-1, indicative of the presence of benzene rings corresponding to eugenol (a phenolic component). The inhibitor exhibited remarkable efficiency, reaching its peak at 96.51% when used with HCl media at a DCL concentration of 15%. This high efficiency is notably reflected in the significant reduction of the corrosion rate from 352.96 mpy to 12.31 mpy in the presence of HCl media.

The influence of addition maja fruit peel extract as inhibitor on the corrosion rate of stainless steel and carbon steel

Corrosion can cause serious damage, such as a piece of equipment or a decrease in tool life. The materials used in an industry, its use can be seen in factory flow pipes that carry a substance, which is one of the factors causing corrosion. The aim of this research is to determine the performance of maja rind extract as an inhibitor of stainless steel and carbon steel corrosion rates, to determine the inhibition efficiency of maja rind extract in controlling the corrosion rate of stainless steel and carbon steel. Method use in this reasearch extraction and polarization. The best concentration in controlling the corrosion rate of SS 304 was obtained at 100 ppm with a corrosion rate of 0.00963 mpy, for SS 316 it was obtained at 100 ppm with a corrosion rate of 0.00521 mpy, while on steel plate it was obtained at 100 ppm with a corrosion rate of 0.00774 mpy. The best inhibitor efficiency on SS 304 can reach 97.6% with the best concentration of 100 ppm, on SS 316 it can reach 99.4% with the best concentration of 100 ppm, and on steel plate it can reach 98.84% with the best concentration of 100 ppm.

Study of corrosion properties of carbon steel, 304 and 316L stainless steels in sulfuric acid and their degradation products

In this study, corrosion properties of carbon steel and stainless steels, and degradation of sulfuric acid by the corrosion mechanism are presented. Carbon steel (CS), 304 stainless steel (SS304), and 316L stainless steel (SS316L) specimens were analyzed through their electrochemical response by using a potentiostat measurement. The specimens were submerged in concentrated 98 wt.% of H2SO4 acid for 0 day to 60 day. The degradation of H2SO4 was determined by its volume change, turbidity, and color due to the corrosion mechanism. Corrosion rate of CS, SS304 and SS316L specimens are 43.237 mm/year, 0.420 mm/year and 0.086 mm/year, respectively. After 60 days, the weight-loss of CS, SS304 and SS316L specimens are 48 wt%, 33 wt% and 0.1 wt%, respectively. Corrosion resistance of the materials are influenced by the passive oxide layer that forms on its surface and associated with electrochemical activity or semiconductive composition. The degradation of H2SO4 acid was observed due to the corrosion process of specimens and related to the turbidity and volume increase while the wt% concentration of H2SO4 acid decreases. In order to make material choices that enable continuous and safe operation of the process, it is important to understand the corrosion mechanism changes.

Anticorrosion Agents for Carbon Steel in Acidic Environments: Synthesis and Quantum Chemical Analysis of New Schiff Base Compounds with Benzylidene.

Novel Schiff bases (SBs), namely, N1,N2-bis(2-(((E)-4-chlorobenzylidene)amino)ethyl)ethane-1,2-diamine (I), N1,N2-bis(2-(((E)-4-(dimethylamino)benzylidene)amino)ethyl)ethane-1,2-diamine (II), and N1,N'1-(ethane-1,2-diyl)bis(N2-((((Z)-4-dimethylamino)benzylidene) amino)methylethane-1,2-diamine) (III), were prepared and characterized by using elemental analysis, IR, and 1H NMR spectroscopy. For assessing carbon steel in diverse settings, with and without inhibitors at varying concentrations, electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP) techniques were employed. The results showed that the synthesized inhibitors effectively decreased the corrosion rate of carbon steel in acidic media and the inhibition efficiency reached up to 93% for compound III at a concentration of 250 ppm. In addition, all prepared compounds were successful as anticorrosion agents, and the inhibition mechanism followed chemisorption from the Langmuir isotherm. The data obtained from the theoretical analysis show that the efficiency of the prepared compounds was in the order III < II < I. Furthermore, quantum chemical calculations were performed to gain insight into the electronic structure of the compounds. The analysis of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) showed that compound III had the highest surface coverage due to its specific molecular structure and spacer. This observation agreed well with the Langmuir adsorption data.

Effects of Ca2+ Ions on the Localized Corrosion of Carbon Steel Influence of the Associated Anion

The corrosion rate of carbon steel under the attack of electrolytic mediums saturated by CO2 at a working temperature of 65 °C under dynamic conditions is studied in this paper. The effect of Ca2+ ions on corrosion rates and their dependency on the associated anion (Cl− or CO32−) with respect to the Ca2+ cation and Na+ are also assessed. A potentiostat/galvanostat associated with a rotor stator in an AISI 1040 steel-ring configuration, rotating at 600 rpm, was used. A linear polarization-resistance technique was applied to calculate the corrosion rate. It is found that the corrosion rate depends not only on the presence of Ca2+, but also on the salt anion added to the electrolytic medium. There was a strong inhibitory effect of the corrosion in the presence of Ca2+ in chloride-free mediums because of an ankerite deposition with a lower solubility compared to siderite. Moreover, it was observed that, even if the corrosion rate increased together with the Cl− concentration, its value depended on the cation introducing the anion. It was higher when Cl− was associated with Na+ compared to when it was associated with Ca2+. We found the following decreasing order in the carbon steel corrosion rate: 2% NaCl + 1380 ppm CaCl2 &gt; 2% NaCl &gt; 2% NaCl + 1360 ppm Na2CO3 &gt; 2% NaCl + 1.25 g/L CaCO3 &gt; 1450 ppm of NaCl &gt; 1380 ppm CaCl2 &gt; 1360 ppm Na2CO3 &gt; 500 ppm CaCl2 &gt; 424 ppm Na2CO3 &gt;&gt; 1.250 g/L CaCO3.