Potentiodynamic Sweep Research Articles

Pitting corrosion of super martensitic stainless steel 00Cr13Ni5Mo2

Purpose – The purpose of this study was to investigate the pitting resistance and assess the critical pitting temperature (CPT) of a super martensitic stainless steel, 00Cr13Ni5Mo2, made in China, considering especially the difference in the pitting corrosion resistance between the domestic super martensitic stainless steel and an imported one. Design/methodology/approach – Potentiodynamic sweep tests were applied to investigate the effects of four NaCl concentrations (weight per cent) of 1, 3.5, 9 and 17, and four testing temperatures of 30, 50, 75 and 90°C on the pitting resistance of the domestic super martensitic stainless steel in the presence of CO2. Potentiostatic sweep tests were utilized to determine the CPT. Furthermore, chemical immersion exposures, implemented according to the appropriate standard were used to evaluate the difference in the pitting corrosion resistance between the domestic super martensitic stainless steel and an imported one. In addition, the morphology of pits was analyzed using a scanning electron microscope. Finding – The pitting potential of the domestic super martensitic stainless steel decreased with an increase in NaCl concentration and temperature in the presence of CO2. The CPT of the domestic super martensitic stainless steel measured by potentiostatic polarization was 41.16°C. Two types of typical corrosion pits, closed pits formed at 35°C and open pits formed at 50°C, were observed. Furthermore, compared to the super martensitic stainless steel made in Japan, the domestic one was better in terms of pitting potential, corrosion rate and the density of the pits, but worse in terms of the depth of the pits, which may result in a risk of corrosion perforation of tubing and casings. Originality/value – The paper highlights that chloride ions, temperature and the presence of CO2 play an important role on the pitting resistance of super martensitic stainless steel.

Electrochemical study of corrosion behavior of graphene coatings on copper and aluminum in a chloride solution

Electrochemical characteristics and corrosion behavior of graphene coatings on Cu and Al in a 0.1M NaCl solution were investigated. The graphene coatings were deposited on a Cu surface by chemical vapor deposition. Multiple graphene layers were then mechanically transferred from the growth substrate, Cu, onto Al surface by a transfer technique. The corrosion stability of graphene coatings was determined by electrochemical impedance spectroscopy and open circuit potential, while the corrosion rate was evaluated using potentiodynamic sweep measurements. Surface morphologies of the graphene coatings were analyzed by scanning electron microscopy and energy dispersive spectroscopy. Obtained results indicate that Cu coated with graphene grown using chemical vapor deposition shows corrosion-inhibiting properties in 0.1M NaCl. On the other hand, Al coated with a multilayer graphene film mechanically transferred from the Cu surface exhibits electrochemical characteristics similar to an Al oxide on bare Al. Better protective properties of graphene coating on Cu compared to the graphene coating on Al were observed, probably due to the breakage of Al oxide film, causing the corrosion of Al to proceed rapidly in the presence of chloride electrolyte.

Electrochemical Study and Modeling of H2S Corrosion of Mild Steel

The internal corrosion of mild steel in the presence of hydrogen sulfide (H2S) represents a significant challenge in oil production and natural gas treatment facilities, but the underlying mechanisms involved in H2S corrosion are still not fully understood. This lack of knowledge makes the prediction, prevention, and/or control of aqueous H2S corrosion of mild steel much more difficult. In the present study, H2S corrosion mechanisms were experimentally investigated in short-term corrosion tests (lasting 1 h to 2 h), conducted in a 1 wt% sodium chloride (NaCl) solution at different pH (pH 2 to pH 5), at different temperatures (30°C to 80°C), under various H2S/N2 gaseous concentration ratios (0 to 10%[v]) and flow rates, using a X65 mild steel rotating cylinder electrode. Corrosion rates were measured by linear polarization resistance (LPR). Corrosion mechanisms were investigated by using potentiodynamic sweeps and by comparison with electrochemical modeling. LPR results showed that corrosion rates increase...

The Effect of Two Amine-Based Corrosion Inhibitors in Improving the Corrosion Resistance of Carbon Steel in Sea Water

This study investigates the effect of two amine-based corrosion inhibitors in reducing the corrosion rate (CR) of 1018 carbon steel in formulated sea water. For discussion purposes, the two inhibitors are named Inhibitor A (belongs to the alkyl pyridine benzyl chloride quaternary family of inhibitors) and Inhibitor B (belongs to the alkyl amines family of inhibitors). The two inhibitors are routinely considered for applications by Saudi Aramco, the world’s largest oil producing and processing company, for reducing its corrosion problems in carbon steel pipelines carrying oil and gas. The experimental apparatus was a circulating flow loop system inside an autoclave. The experimental work was performed at pH 8.2, 55 °C, and 1000 rpm. The inhibitors were evaluated at three different concentrations of 5, 10, and 15 ppm. The CR was determined using the weight loss method and electrochemical methods such potentiodynamic sweep and linear polarization resistance. The experimental results indicate that Inhibitor B reduced the CR more than that of Inhibitor A.

Sodium Chloride Concentration Effects on General CO2Corrosion Mechanisms

The general carbon dioxide (CO2) corrosion rates of C1018 (UNS G10180) carbon steel have been measured for sodium chloride (NaCl) concentrations 3 wt% to 25 wt% at 20°C, pH 4.0, 5.0, and 6.0. Experimental results showed that high salt concentrations decreased the general CO2 corrosion rate significantly and nonlinearly. Potentiodynamic sweep analysis shows that both cathodic and anodic processes were retarded. Flow velocity effects on general CO2 corrosion rate were minimized as a result of an increase of salt concentration. No effect of high salt concentration on initiation of localized attack was detected.

A Novel Method to Mitigate the Top-of-the-Line Corrosion in Wet Gas Pipelines by Corrosion Inhibitor within a Foam Matrix

Top-of-the-line corrosion (TLC) has been a serious issue for the oil and gas industry. Conventional inhibition techniques are expensive and often do not seem to provide enough protection to the steel surface at the top of the pipe. A novel idea is to inject the corrosion inhibitor within a foam matrix. The foam slug is formed first at an injection port and carried along the pipe by the gas phase. This process ensures homogeneous delivery of the inhibitor to the pipe wall along pipe sections suffering from TLC. This paper presents a comprehensive study performed in an innovative glass cell setup which consisted of a foaming cell and a corrosion cell to simulate intermittent contact between the foam and the steel surface. Corrosion measurements were performed using electrochemical techniques (electrochemical impedance spectroscopy [EIS], linear polarization resistance [LPR], potentiodynamic sweep) and electrical resistance (ER) measurements to determine the inhibitive performance of investigated inhibitor t...

Electrochemical corrosion behavior of X52 and X60 steels in carbon dioxide containing saltwater solution

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 CO2 containing saltwater at pH 4.4 and 50 ºC. 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.

In situ pH measurements with hydrous iridium oxide in a rotating ring disc configuration

Many chemical reactions are pH dependent and for electrochemical reactions taking place at an electrode surface, changes in the near surface pH can be decisive for their outcome. Near surface pH changes have successfully been utilised for formation of oxide films and to control the shape and morphology of the deposit. The mechanistic insight into such processes is hampered by the difficulty to measure the local pH in situ. In the present paper the rotating ring disc electrode (RRDE) configuration is used to measure the near surface pH for two model reactions, hydrogen evolution and oxygen reduction. Iridium oxide is electrodeposited on the titanium ring and used as the pH sensing material. At low current densities and therefore low hydroxide ion concentrations, the pH response is rather slow, limiting the applicability of potentiodynamic sweep experiments under such conditions. At higher current densities a linear relationship between the logarithm of the current and pH is found. Tracking of small pH changes can be made by step experiments where the response is measured as a function of time and steady state conditions can be assured. Key issues for successful use of the RRDE configuration with iridium oxide as the pH sensing material are pre-conditioning of the ring electrode to obtain well defined redox properties of the film and choice of ring substrate onto which the iridium oxide is deposited.

Fast visualization of the mass transfer processes at the electrode/electrolyte interface with a Mach-Zehnder interferometer

A Mach-Zehnder interfeometer is employed to visualize the mass transfer processes at the electrode/electrolyte interface during the potentiodynamic sweep of the Pt electrode in 0.1 mol dm−3 K4Fe(CN)6 with 0.5 mol dm−3 KCl solution at 20 mV s−1. The changes of solution’s refractive index, brought about by the mass transfer during the reaction, can be recorded in situ in interferograms. The distributions of the optical path difference are obtained by numerical reconstruction of interferograms to reflect changes of solution’s refractive index and the mass transfer processes. The mass transfer of [Fe(CN)6]4− and [Fe(CN)6]3− is presented visually. This method provides a new approach to detect the mass transfer processes at the electrode/electrolyte interface in real-time.

Corrosion resistance and electrodeposition behavior of electrodeposited nickel‐cobalt‐iron alloys

PurposeThe purpose of this paper is to investigate the corrosion resistance and the electrodeposition behavior of electrodeposited nickel‐cobalt‐iron alloys. Also, to compare the electrodeposition of ternary nickel‐cobalt‐iron alloy from acidic sulfate bath onto a steel substrate with the characteristics of Co‐Fe electrodeposits.Design/methodology/approachThe investigation of electrodeposition was carried out using cyclic voltammetry and galvanostatic techniques, while potentiodynamic polarization resistance and anodic linear sweep voltammetry techniques were used for corrosion study. The phase structure was characterized by means of X‐ray diffraction analysis. The surface morphology and chemical composition of the deposits were examined by using scanning electron microscopy and atomic absorption spectroscopy, respectively.FindingsThe obtained results revealed that the Ni‐Co‐Fe alloys consisted of a mixture of iron (Fe10.8Ni) and (FeCo) phases. It was found that the obtained Ni‐Co‐Fe alloy exhibited a more‐preferred surface appearance and better corrosion resistance, compared to the Co‐Fe alloy that was electrodeposited under similar conditions.Practical implicationsNi‐Co‐Fe alloy was successfully electroplated from a sulfate bath. This alloy showed better anticorrosion properties compared to Co‐Fe deposits. The Ni‐Co‐Fe alloy could be used advantageously in industry, e.g. the automotive industry. The coating also has particular interest due to it is ability to exhibit stable magnetic properties.Originality/valueThe paper evaluates the effect of electrodeposition of the ternary alloy on the corrosion behavior of electroplated steel. To date, there has been little research on this issue. It was found that the presence of Ni could increase the corrosion resistance of steel.

Dynamic Sensing of Localized Corrosion at the Metal/Solution Interface

A Mach-Zehnder interferometer is employed to detect localized corrosion at the metal/solution interface in the potentiodynamic sweep of the iron electrode in solutions. During the electrochemical reactions, local variations of the electrolyte's refractive index, which correlate with the concentration of dissolved species, change the optical path length (OPL) of the object beam when the beam passes through the electrolyte. The distribution of the OPL difference was obtained to present the concentration change of the metal ions visually, which enable direct evidence of corrosion processes. The OPL difference distribution shows localized and general corrosion during the anodic dissolution of the iron electrode in solutions with and without chloride ions, respectively. This method provides an approach for dynamic detection of localized corrosion at the metal/solution interface.

Electrochemical behavior and mechanism of CO2 corrosion on P110 steel in simulated oilfield solution

PurposeThis paper aims to further investigate the behavior and mechanism in simulated oilfield solution on CO2 corrosion of P110 steel at various temperatures by potentiodynamic sweep and electrochemical impedance spectroscopy (EIS) measurements, especially discussing the influence of the coverage fraction of corrosion film.Design/methodology/approachPotentiodynamic sweep and EIS measurements were applied to investigate the behavior and mechanism with the effect of temperature on CO2 corrosion of P110 steel in simulated oilfield solution at 30°C, 60°C and 90°C.FindingsThe corrosion parameters of polarization curves, such as corrosion potential (Ecorr), corrosion current density (icorr), anodic and cathodic branches slopes (βa and βc), were analyzed and discussed in detail. In addition, the equivalent circuit models and ZsimpWin software were utilized to fit and analyze the Nyquist plots. The plots showed that corrosion potential shifted more negatively as temperature increased. The corrosion current density (icorr) initially increased and then decreased with the increase of temperature. The impedance spectra measured at various temperatures had different time constants.Originality/valueThe paper highlights that the coverage fraction θ of corrosion film is one most important and key variable influencing CO2 corrosion mechanisms.

Estudio de corrosión galvánica en pares latón/acero inoxidable y latón/fundición de hierro

Corrosion attack in heat exchanger systems is a topic of main interest for the maintenance in each industrial plant. These are multigalvanic systems with particular geometric and fluidodynamic complexity. Corrosive damages include zinc selective dealeation in copper alloys. In order to explain zinc dealeation attack, this paper deals with laboratory scale testing, characterization and interactions between two copper and zinc alloys (Yellow brass –UNS C268– and Admiralty brass –UNS C443–) compared to AISI 316 stainless steel and cast iron. The tests were performed at 20 °C in 1.5 % NaCl and 1.5 % Na 2 SO 4 solutions, pH 8 and each material was characterized by potentiodynamic sweeps. The couples are analyzed by studying transient galvanic currents. We conclude about the cause of the analyzed pathology, brass protection potential ranges and its coupling compatibility with other metals.

Electrochemical Behavior of Tubular Steel Corrosion in Brine Containing High Contents of H<sub>2</sub>S and CO<sub>2</sub>

There were little works about electrochemical corrosion behaviors that appeared in high H2S and CO2 containing environment. In this work, the electrochemical behaviors of tubular steel API-P110 in buffered acidic NaCl solutions saturated with high H2S and CO2 containing gases, were investigated by potentiodynamic sweep technique. Analysis of the results shows corrosion density declines with increasing CO2 content in H2S/CO2. The corrosion potential of steel moves towards more negatively with the increase of CO2 content in H2S/CO2. In pH 2.9 solution, Passivity appears in high H2S and CO2, but no passivity shows in due to decreasing in high H2S. In pH 5.3 solution, cathodic liming density comes out and increases with the increasing CO2 content in H2S/CO2, however, no cathodic liming density comes out in H2S.

Effects of sulphide ion on the corrosion behaviour of X52 steel in a carbon dioxide environment at temperature 40 °C

The electrochemical behaviour of X52 steel in the presence of sulphide at 40 °C in a CO 2 environment was investigated using the methods of linear polarization resistance (LPR), potentiodynamic sweep, electrochemical impedance spectroscopy (EIS). In addition, the surface of X52 steel was also studied using scanning electron microscopy (SEM). The results showed that the corrosion rate of X52 steel increased with increasing concentration of sulphide ion. Potentiodynamic curve showed that there were changes in cathodic branch due to the change in the nature of cathodic reaction in the presence of sulphide ion. EIS analysis showed the higher sulphide ion concentration, the higher adsorbed species on the steel surface that contributed in the cathodic reaction. Furthermore, SEM results showed crevices on the scale which indicated pitting tendency in sulphide ion solutions. The less protective film, probably mackinawite, also contributed to the increase of corrosion rate in the presence of sulphide ion.

A microelectrochemical scanning flow cell with downstream analytics

The combination of a capillary based microelectrochemical flow cell system and downstream UV–vis analytics allows obtaining synchronized electrochemical and spectroscopic data in a fully automated mode. This method combination can be generally applied to microelectrochemical studies in which an electrochemical species is released or consumed during the electrochemical reaction. For the example of pure zinc surfaces, the characterization of the integrated spectroscopic system is presented with a Zn 2+ detection limit below 0.1 μmol l −1 using Zincon as complexing agent. A parameter screening of the effect of pH in the range of 6.6–9.0 in borate buffer reveals a linear increase in zinc dissolution with proton concentration but a distinct step in the open circuit potential from the active state (around −700 mV SHE, pH 6.6–7.1) to the passive state (around −300 mV SHE, pH 7.4–9.0) indicating the formation of a closed passive layer. This mechanism is strongly influenced by sulfate anions which increase the dissolution rate of the passive film and promote the active state as monitored by the dissolution profile and OCP (open circuit potential) values. Within the scope of this parameter variation, the congruency between OCP transients, potentiodynamic sweeps and time resolved dissolution profiles is discussed.

External control of anodic dissolution mechanism of 100Cr6 in nitrate/chloride mixed electrolytes

The anodic dissolution of 100Cr6 steel in neutral electrolytes containing sodium chloride and sodium nitrate was investigated potentiodynamically and galvanodynamically with a rotating disc electrode at room temperature. The total concentration of the mixed electrolyte was 3 mol L-1 with variation of chloride/nitrate mole ratios. The potentiodynamic linear sweep voltammograms (LSVs) in mixed electrolytes are similar to the LSVs in pure chloride electrolyte at lower current densities and switch to behaviour observed in pure nitrate electrolytes at higher current densities. Provided that both anions are present, it seems that the dissolution reactions at the steel anode are determined by the interface layer only. The effect of these layers on surface quality and current efficiency was also investigated in a flow channel applying galvanostatic pulses. An evidence for different dissolution mechanisms can be seen with an important influence of duty cycle and flow conditions. This allows external control of the desired dissolution mechanism in mixed electrolytes.

Effect of nitrate ion on corrosion inhibition of mild steel in simulated cooling water

Corrosion inhibition of mild steel by sodium nitrite in simulated cooling water (SCW) containing chloride ion was investigated. Electrochemical techniques such as corrosion potential (Ecorr) measurement and potentiodynamic sweep experiments were used. The experimental parameters were concentration of the inhibitor, pH of the aqueous media and soaking time. Nitrite inhibited mild steel corrosion in near neutral and alkaline (pH 6 and above) SCW and accelerated corrosion in acidic media (pH 4 and below). Inhibition activity increased with the increase of nitrite concentration up to 500 ppm, and afterwards remained more or less constant at pH 6 and above. In stagnant SCW, maximum corrosion inhibition was observed at pH 8 for all concentration of NaNO2. Inhibition action of NaNO2 was found to increase with the increase of soaking time up to 24 hours, and afterwards it remained more or less constant at all nitrite concentrations at and above pH 6. Based on the experimental results, mechanisms of action of NaNO2 on mild steel corrosion inhibition in SCW have been proposed.Keywords: Corrosion; Potentiodynamic sweep; InhibitorDOI = 10.3329/cerb.v14i2.4813Chemical Engineering Research Bulletin 14 (2010) 87-91

Multilayer Corrosion of Aluminum Activated by Lead

Segregation of Pb as a nanofilm between the thermal oxide and the metal substrate as a result of high temperature heat-treatment is known to activate aluminum alloys anodically in chloride solution. The relationship between the oxidation peaks in the polarization curve and corrosion morphology was investigated by the use of a video technique during electrochemical polarization. A model binary Al–Pb alloy containing 20 ppm Pb, which was annealed at , showed two oxidation peaks at −0.95 and −0.88 . The video measurements revealed superficial etching of the surface by selective oxidation of the aluminum metal twice, followed each time by repassivation, as the two oxidation peaks were resolved during anodic potentiodynamic sweep. Ex situ scanning and transmission electron microscopy of the corroded specimens indicated that the first layer of etching followed the Pb film and undermined the thermal oxide, which remained attached to the metal surface at discrete locations, thereby forming a crevice. The second layer of attack was caused by crevice corrosion of the aluminum substrate in the crevice formed by the preceding oxidation process, which resulted in the removal of the attached thermal oxide film. The exposed aluminum substrate started to pit as the pitting potential was finally exceeded.

Corrosion resistance of the anti‐sulfide steel in the CO2/H2S containing solutions

AbstractThe present work primarily investigates the corrosion characterization of the common P110 steel and the anti‐sulfide P110SS steel in CO2‐containing solution with or without hydrosulfuric acid (H2S) at 70 °C. The electrochemical techniques such as potentiodynamic polarization sweep and electrochemical impedance spectroscopy (EIS) were used to disclose the differences of the corrosion mechanisms between both P110 and P110SS steels in CO2‐containing solution with various additions of H2S. The EIS data fitted by ZsimpWin software were analyzed and discussed. The experimental results indicated that H2S could accelerate and also inhibit the corrosion attack according to the changes of corrosive environments.