Steel In Alkaline Media Research Articles

Corrosion inhibition behaviour of synthetic 2-(phenylsulphonamido)-3-methylbutanoic acid on mild steel in alkaline solution

The corrosion inhibiting behaviour of synthetic 2-(phenylsulphonamido)-3-methylbutanoic acid (PSMBA) on mild steel in the presence of 0.1 M KOH was investigated using combined gravimetric, electrochemical and theoretical simulation corrosion monitoring methods. The gravimetric data showed that the inhibitor effectively protected the metal from alkaline corrosion and that the inhibition ability depended on concentration increase and reduced gradually with prolonged immersion time. The electrochemical impedance spectroscopy results show that the charge transfer resistance increased with the addition of the inhibitor while potentiodynamic polarization results showed that the corrosion current density decreased upon the addition of the inhibitor, theoretical simulation results revealed a low and comparable energy gap between the LUMO and HOMO energies. All these showed that 2-(phenylsulphonamido)-3-methylbutanoic acid functioned as a good corrosion inhibitor for mild steel in alkaline medium.

Electrochemical investigation of ceria nanoparticles as a corrosion inhibitor for steel in alkaline medium

AbstractThis work investigates the synthesis and the corrosion inhibitor efficiency ceria nanoparticles may exert on steel reinforcement in an alkaline solution of saturated Ca(OH)2 + 0.5 M CaCl2 up to 50°C. The corrosion mechanisms are thoroughly investigated by electrochemical and various characterization techniques. The electrochemical results show that ceria nanoparticles act as an anodic inhibitor and provide maximum inhibition efficiency (80%) at a concentration of 800 ppm. The resulting surface is smooth and free from corrosion products due to the formation of a physically adsorbed film according to the thermodynamic calculations.

Electrochemical behavior of nickel containing passive oxide films on carbon steel in alkaline medium

The passive oxide film formed on the carbon steel surface in lithiated water was modified by the incorporation of nickel ions by hydrothermal deposition at 250°C. The aim was to verify to what extent the in-situ oxide films grown in presence of nickel ions improved the corrosion resistance of the carbon steel substrate in comparison to the films formed in the absence of nickel ions at different exposure times. Grazing incidence-X-ray diffraction studies confirmed the formation of the spinel phase in the passive oxide film. X-ray photoelectron spectroscopy revealed the presence of the nickel ions in the oxide lattice. The electrochemical behavior of the oxide films formed on the carbon steel surface was studied using electrochemical impedance spectroscopy and potentiodynamic anodic polarization methods. Tafel plot extrapolations from the potentiodynamic anodic polarization plots revealed a substantial difference in the corrosion resistance of the films formed on carbon steel substrate in the presence of nickel ions. The oxides grown in the absence and in the presence of nickel ions exhibited similar corrosion current densities but showed a higher polarization resistance value in the presence of nickel ions. The semiconductor properties of these oxides were characterized by Mott Schottky measurements and the results are presented in detail in this paper.

Mo Effect on Natural Passivation and Corrosion Behavior of Duplex Stainless Steels in Alkaline Media

The role of Mo in the natural passivation behavior and pitting corrosion resistance of duplex stainless steels (DSSs) in alkaline medium was investigated by X-ray photoelectron spectroscopy and electrochemical analyses as a function of immersion time. It is shown that the Mo participated directly in the formation process of natural passive film, which affected the chemical distribution and thickness of the film by modifying the contents of other species (e.g. Cr oxide). With the increasing of prepassivation time, the oxidized Cr species were gradually enriched in the passive film, and the corrosion resistance of DSSs in alkaline solution containing Cl− was enhanced. Mo greatly improved the pitting corrosion resistance and the tolerance to Cl− attack of the passive film formed on DSS surface by inhibiting the initiation and growth of pitting.

Further studies on the anaerobic corrosion of carbon steel in alkaline media in support of the Belgian supercontainer concept

AbstractIn the Belgian supercontainer concept, a carbon steel overpack surrounds high‐level radioactive waste and spent fuel containers and is encased in a cementitious buffer material. Research has been carried out to characterise the anaerobic corrosion of carbon steel in an anoxic artificial alkaline porewater that simulates the cementitious buffer material and also in solid cement matrices, in the presence of chloride and the sulphur species expected in the groundwater. The current study focuses on recent results. Specifically, it provides an update on the long‐term corrosion rates obtained from gas generation measurements (including new data from higher‐sensitivity autoclaves) and weight loss measurements and provides results of postmortem analysis of dismantled cells. The behaviour of the system is discussed, focusing on the effects of the solution chemistry, precorrosion treatments and γ radiation on corrosion rates, the electrochemical response of the steel when irradiated, and the morphology of the corrosion product. The corrosion rate was lower in cement than in an aqueous system. Radiation affected the corrosion potential and the morphology of the corrosion product.

Corrosion-Electrochemical Behaviour of Low-Alloy Steel in Alkaline Media

Corrosion-Electrochemical Behaviour of Low-Alloy Steel in Alkaline Media

Adsorption Isotherm and SEM Investigating of Cucurbit[n]Urils Based Corrosion Inhibitors with Gossypol for Mild Steel in Alkaline Media Containing Chloride Ions

This article showed that new mixed inhibitor type of cucurbit [n] urils based corrosion inhibitors with gossypol at the proportion of 50:50 is excellent efficiency for mild steel in in alkaline media containing chloride ions. The Polarization Resistance results suggest that this inhibitor decreased the rate of anodic mild steel dissolution and cathodic hydrogen evolution. Increased activation energy suggested that inhibitors adsorb physically during the first step of the adsorption process.

Summary of studies on the anaerobic corrosion of carbon steel in alkaline media in support of the Belgian supercontainer concept

ABSTRACTIn the Belgian supercontainer concept, a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research has been carried out to investigate and measure the rate of anaerobic corrosion of carbon steel in an artificial alkaline porewater that simulates the aqueous phase in the cementitious buffer material and also in solid cement matrices. This paper highlights the main features of the programme and presents some recent results from the analysis of several samples, including two 20-year-old steel in cement samples, which showed that under anoxic conditions there is no localised corrosion or incorporation of iron into the surrounding cement, even in the presence of 20 000 ppm chloride in the porewater.This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

Influence of the РH Value of the Medium on the Inhibition of Corrosion in Steel Modified by Polyhexamethylene Guanidines

It is shown that the corrosion rate of steel in the presence of polyhexamethylene guanidines decreases as the concentration of polyelectrolytes increases (this effect is more pronounced in acid media). The modification of polyhexamethylene guanidine with carboxylic and phosphonic groups leads to an increase in its inhibiting effect and, moreover, the polyhexamethylene guanidine modified by phosphonic groups exhibits quite high inhibiting properties under the conditions of corrosion of steel in alkaline media, which is explained by its polyampholytic properties. The comparison of these results with the corresponding adsorption isotherms reveals the adsorption nature of the inhibiting effect of polyelectrolytes. It is shown that the inhibiting effect of polyhexamethylene guanidine modified by phosphonic groups is connected with the blocking model. In the other cases, we observe deviations from this model, which possibly can be explained by the action of activation and conformation factors.

Inhibition effect of some trees cultivated in arid regions against the corrosion of steel reinforcement in alkaline chloride solution

The effect of aqueous extract of some trees cultivated in arid regions against the corrosion of carbon steel in alkaline medium simulating the interstitial solution of concrete contaminated with chlorides was investigated using various analytical and electrochemical techniques. Mott-Schottky analysis shows the formation of a passive layer on the metallic surface. EIS results suggest an increase in the corrosion resistance of carbon steel in the presence of plants extract comparatively to the blank systems. Furthermore SEM and EDS analyses corroborate these results. This important inhibition behaviour can be related to differential phenols richness in these plants (HPLC chromatogram).

Pitting corrosion and stress corrosion cracking study in high strength steels in alkaline media

Steel reinforcement in concrete is protected from corrosion by passivation due to the high alkalinity of the cement pore solution, but the presence of aggressive ions as Cl− could induce pitting corrosion processes thus decreasing the durability of the structure. This also occurs for prestressing concretes but the risk to suffer pitting corrosion in presence of aggressive ions, and hence stress corrosion cracking (SCC), increases due to the external mechanical load. The study of the corrosion processes by classical methods involves the determination of pitting potential (E pit) or the polarization resistance monitoring during long periods (i corr). However, the large number of parameters, which could potentially influence the determination of the E pit or the i corr values, result in a great variety of results in literature. The present study proposes a simple and reliable method to evaluate the susceptibility to suffer pitting corrosion process and stress corrosion cracking by the induction of pitting corrosion process by cyclic voltammetry. The pitting corrosion intensity is evaluated by means of the charge during the corrosion process, and related with the weight loss and the decrease of the mechanical properties of the steel under external load. The results show a linear and a volcano trend when pitting corrosion process and stress corrosion cracking are respectively evaluated.

Hybrid sol–gel coatings for corrosion protection of hot-dip galvanized steel in alkaline medium

Two distinct organic–inorganic hybrid (OIH) matrices were synthesised using the sol–gel method and deposited on hot-dip galvanized steel (HDGS) by dip-coating. These OIHs, called ureasilicates, U(X), and amino-alcohol-silicates, A(X), were obtained using a functionalised siloxane and five oligopolymers with different molecular weights (MWs). Besides pure OIH coatings, HDGS samples were coated with OIHs doped with Cr3+, which was tested as a corrosion inhibitor. The OIH coatings deposited by one and three dip steps were assessed by electrochemical studies (polarisation resistance and macrocell current) in mortar in order to compare their performance. The SEM results were consistent with the data obtained by GD-OES and with the electrochemical analyses. The results indicated that the HDGS samples coated with OIHs show enhanced corrosion resistance in highly alkaline environment when compared to uncoated samples. The coatings involving the use of OIH matrices based on U(X) gels show superior corrosion behaviour when compared to the matrices based on A(X). The lowest and the highest corrosion rates were found for HDGS samples coated by one dip step of U(X) and for three dip steps of A(X) doped with Cr3+, using oligopolymers with MWs of 400 and 900, respectively.

Alkaloid and Non Alkaloid Extracts of Solanum melongena Leaves as Green Corrosion Inhibitors on Carbon Steel in Alkaline Medium

The corrosion and inhibition behavior of Carbon steel (CS) in high alkaline solution [Sodium trioxocarbonate (IV)] in the presence of alkaloid and non alkaloid extracts of Solanum melongena leaves have been studied using conventional methods - mass loss and gasometric techniques. The results indicate that the extracts inhibit the corrosion of Carbon steel. However, the Alkaloid extract of Solanum melongena leaves (AESML) exhibits higher maximum inhibition efficiency of 81.1% than Non alkaloid extract of Solanum melongena leaves [NAESML] (65.1%) at 3.0 g/L concentration. Inhibition efficiency increase with increasing concentration of extracts but decreased with rise in temperature. Inhibition mechanism was deduced from the activation and thermodynamic parameters that govern the process. Adsorption of extract on the CS was found to obey the Langmuir adsorption isotherm. The phenomenon of physical adsorption is proposed from the obtained thermodynamic parameters.

Effect of sulphur species on anaerobic corrosion of carbon steel in alkaline media

In the Belgian Supercontainer concept for disposal of vitrified high level radioactive waste and spent fuel, a carbon steel overpack will surround the waste containers and be encased in a cementitious buffer material. In previous work the effects of radiation, temperature and chloride concentration on the anaerobic corrosion rate of carbon steel in an artificial alkaline porewater were measured and recently the effects of sulphur containing species, particularly sulphide and thiosulphate, on the anaerobic corrosion rate of aerobically precorroded carbon steel have been studied. Corrosion rates were measured by monitoring hydrogen evolution, by applying electrochemical methods and by gravimetric analysis. Corrosion product layers formed after several years’ exposure were analysed using focused ion bombardment (FIB) and SEM/EDX analysis. This paper summarises recent results, for experiments with and without sulphur species present. No increase in the anaerobic corrosion rate of pre-corroded carbon steel in the presence of sulphide or thiosulphate was measured.

Low energy SIMS characterization of passive oxide films formed on a low-nickel stainless steel in alkaline media

Low-energy secondary ion mass spectrometry (SIMS) was used to study the oxide films formed on a low-nickel austenitic stainless steel (SS), potential replacement to conventional AISI 304 SS in reinforced concrete structures (RCS) that are subjected to aggressive environments. The effect of carbonation and the presence of chloride ions were studied. The oxide films formed a chemically gradated bi-layer structure with an outer layer predominately constituted by iron oxides and an inner layer enriched in chromium oxides. Chloride ions were not found in the oxide film but did have an effect on film structure and thickness.

The anaerobic corrosion of carbon steel in alkaline media – Phase 2 results

In the Belgian Supercontainer concept a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research was carried out to investigate and measure the rate of anaerobic corrosion of carbon steel in an artificial alkaline porewater that simulates the aqueous phase in the cementitious buffer material. The corrosion rates were measured by monitoring hydrogen evolution using a manometric gas cell technique and by applying electrochemical methods. Phase 2 of the programme has repeated and extended previous Phase 1 measurements of the effects of radiation, temperature and chloride concentration of the anaerobic corrosion rate. This paper provides an update on the results from Phase 2 of the programme. The results confirm previous conclusions that the long-term corrosion rate of carbon steel in alkaline simulated porewater is determined by the formation of a thin barrier layer and a thicker outer layer composed of magnetite. Anaerobic corrosion of steel in cement requires an external supply of water.

Electrochemical and analytical investigation of passive films formed on stainless steels in alkaline media

Passive films were grown in potentiodynamic mode, by cyclic voltammetry on AISI 316 and AISI 304 stainless steels. The composition of these films was investigated by X-ray photoelectron spectroscopy (XPS). The electrochemical behaviour and the chemical composition of the passive films formed by cyclic voltammetry were compared to those of films grown under natural conditions (by immersion at open circuit potential, OCP) in alkaline solutions simulating concrete. The study included the effect of pH of the electrolyte and the effect of the presence of chloride ions. The XPS results revealed important changes in the passive film composition, which becomes enriched in chromium and depleted in magnetite as the pH decreases. On the other hand, the presence of chlorides promotes a more oxidised passive layer. The XPS results also showed relevant differences on the composition of the oxide layers for the films formed under cyclic voltammetry and/or under OCP.

State of the Art on Cactus Additions in Alkaline Media as Corrosion Inhibitors

This research in progress includes results on the corrosion performance of reinforcing steel in alkaline media when two different dehydrated cacti (Opuntia ficus-indica—Nopal—and Aloe Vera) were used as additions in pH 12.5 and 13.3 solutions and in concrete. The dehydrated cactus addition was mixed at different concentrations by either solution or cement mass (0.10%, 0.25%, 0.5%, 1.0%, and 2.0%). Half-cell potentials and LPR measurements were performed at different time periods to characterize the possible corrosion inhibiting effect of the cactus additions tested in such alkaline media. Results showed good corrosion inhibiting effect of dehydrated Nopal on reinforcing steel, in all tested solutions, when chloride ions are present. Aloe Vera did show also corrosion inhibiting improvements in some extent. The addition of such cactus led to an apparent formation of a denser and more packed oxide/hydroxide surface layer on the steel surface that decreased corrosion activity. This oxide/hydroxide layer growth was confirmed by microscopic evaluation of the metal surface layer performed at the end of the research program. The preliminary findings suggest that adding Nopal at concentrations between 1% and 2%, by mass, might be suitable for durability enhancing applications in alkaline media, especially in concrete structures.

Laser surface treatment to inhibit observed corrosion of reinforcing steel in sulphate: alkaline media

PurposeThe effect of chlorides on corrosion of reinforcing steel is well documented in the literature. However, few studies have focused attention on the effect of sulphates on the corrosion of low carbon steel in alkaline media. This paper aims to address this issue.Design/methodology/approachThis paper describes the results of the investigation into the corrosion behaviour of low carbon steel (typically used as reinforcing steel), exposed to alkaline media at a pH of 9 and 12 with varying concentrations of sulphate and chloride ions, as well as, in sulphate only solutions. An attempt was made to inhibit corrosion of steel exposed to the corrosive media using laser surface treatment of the steel specimens. Mass loss tests and electrochemical tests were conducted to evaluate the effect of sulphate only and the combined effect of sulphate and chloride ions in an alkaline media on steel.FindingsIt was found that sulphate ions could cause corrosion of steel in alkaline media. The severity of the attack increased with increasing sulphate ion concentrations, as well as with combinations of sulphate and chloride ions. The pH 12 conditions seem to show much more critical attack with evidence of pitting corrosion as compared to uniform corrosion for test conditions at a pH of 9. The attempt to inhibit the observed corrosion of steel exposed to the corrosive high alkaline media containing sulphate ions on their own and in combination of chloride ions by laser surface treatment proved to be successful.Originality/valueThe research undertaken here adds to the body of knowledge relating to the effect of sulphate ions on reinforcing steel corrosion in highly alkaline media. Most literature points out that sulphate ions on their own do not have a corrosive effect, but rather, a passivating effect!

Electrochemical response of natural and induced passivation of high strength duplex stainless steels in alkaline media

The passivation of two high strength duplex stainless steels (HSSS) was investigated in alkaline solutions simulating the pore solution of concrete by the growth of natural and induced passive films. Induced passive films were generated both by cyclic voltammetry and by chronoamperometry. Natural passive films were spontaneously grown by the immersion of the steel in the alkaline electrolyte. These passive layers were characterised by electrochemical impedance spectroscopy, corrosion current density (i corr) and corrosion potential (E corr) monitoring. The effect of significant parameters, such as the pH in the HSSS/alkaline solution interface, the composition of the duplex stainless steels and the ageing of the passive layer, on the electrochemical performance of both induced and spontaneously grown passive films has been analysed. The increase of alkalinity highly influences the electrochemical performance of the passive film by promoting the formation of a passive layer with a less resistant electrochemical response. The electrochemical behaviour of the passive layer is also affected by the alloying elements like Mo or Ni. Both natural and induced passive films show similar electrochemical trend with respect to significant parameters such as the pH and the composition of the steel. The ageing of the spontaneously grown passive layer promotes a higher resistive electrochemical response which might be related to the enrichment of the passive layer in non-conducting (or semi-conducting) oxides.