Corrosion of hot-rolled 430 stainless steel in HCl-based solution

The mixtures of hydrochloric acid and hydrogen peroxide were employed as the environmental friendly pickling solution for 430 hot-rolled stainless steel in this study. Increase of HCl concentration accelerates the corrosion rate of base metal, however aggravates the intergranular attack in sole hydrochloric acid solution. Addition of oxidant (H₂O₂) boosts the corrosion potential of stainless steel significantly resulting in the change of electrode action. At high oxidant content (0.6?mol?l^?1 H₂O₂), a corrosion product film accumulates onto the surface and the corrosion is then governed by the mass-transport at the film/stainless steel interface. The random dissolving of metal ions because of the film leads to brightening of stainless steel surface and the local corrosion is suppressed.     

Säureinhibitoren. III. Einfluß von quartären Ammoniumsalzen auf die Wasserstoffaufnahme von unlegiertem Stahl in H2S-freier und H2S-gesättigter Ameisensäure

Acid inhibitors. II. Influence of quarternary ammonium salts on the hydrogen absorption of mild steel in H₂S-free and H₂S-saturated formic acid The influence of quaternary ammonium compounds (benzylpyridinium chloride, benzylquinolinium halides, p-dodecylbenzylquinolinium chloride, benzylisoquinolinium chloride, tri-n-butylbenzylammonium halides, benzyldabcolinium chloride) on the rate of metal dissolution and absorption of corrosion hydrogen in the metal was studied at mild steel in chloride containing 10% formic acid at 25 °C in the presence and absence of H₂S. Generally the same effects were observed like in the system steel/hydrochloric acid. Depending on the kind of inhibitor the presence of H₂S increased or decreased the efficiency of inhibitors to block the H-absorption. Regardless of the presence of H₂S p-dodecylbenzylquinolinium chloride and benzylquinolinium iodide exhibited the best efficiencies in decreasing the rate of metal dissolution and inhibiting the H-absorption in the metal.     

Korrelationsbetrachtungen zum Einfluß von Säureinhibitoren auf die Metallauflösungsgeschwindigkeit und die Kinetik der Wasserstoffabsorption

Considerations on the correlations between inhibition of metal dissolution and hydrogen absorption in the use of acid inhibitors Evaluating literature data on the impact of 53 quarternary ammonium salts, 13 aliphatic and aromatic aldehydes and 12 aliphatic and aromatic ketones on the inhibition of the rate of metal dissolution and the hydrogen permeation currents at steel in H₂S-free and H₂S-saturated 16% hydrochloric acid at ambient temperature, it is demonstrated by rank correlation considerations that there is no correlation between activity in blocking the metal dissolution rate and efficiency in decreasing the hydrogen absorption rate of the metal. Furthermore, there is no correlation between antipromotor/promotor-efficiency at the free corrosion potential and at cathodic polarization in H₂S-free and H₂S-saturated acid. Problems of H-absorption therefore have to be investigated for any particular case under conditions as close to the practice as possible.     

New evidence on the role of catalase in Escherichia coli-mediated biocorrosion

The role of catalase on the microbiologically influenced corrosion mechanism by Escherichia coli (E. coli) has been examined, employing wild type and catalase-deficient cells. The bacteria were cultured for different times in the presence of AISI 316L stainless steel samples. The morphologies of the metallic surfaces covered by biofilms were studied by optical microscopy. The localized corrosion catalyzed by the bacteria was followed by scanning electron microscopy after immersion in the bacterial culture for different times. Susceptibility to corrosion was further investigated by potentiodynamic measurements. It was found that wild type E. coli is more aggressive than the mutant one, suggesting a role for catalase in increasing the kinetics of the cathodic reaction and, consequently, the global corrosion process. This correlates with oxygen uptake kinetics, as determined by differential pulse voltammetry on a pyrolytic graphite electrode modified with cobalt phthalocyanine, which was higher in the presence of wild type E. coli. When H₂O₂ was deliberately added to the culture medium, wild type E. coli catalyzed oxygen disproportionation more efficiently than the mutant derivative, thus limiting H₂O₂ accumulation in the medium and, hence, bacterial poisoning. In fact, the reduced adhesion of mutant cells to the metal substrate is apparently the result of H₂O₂ accumulation in the culture broth. Thus, the rapid consumption of oxygen and peroxide in the presence of wild type E. coli is associated with the catalysis of H₂O₂ disproportionation to water and oxygen. On the stainless steel, however, a dual mechanism of oxygen reduction, i.e. through formation of hydrogen peroxide and by formation of water, is also considered.     

Zur Redoxwertigkeit des Sauerstoffs an Nickelproben in 1 n Salz-und Schwefelsäure

Redox valence of oxygen on nickel specimens in 1 n hydrochloric and sulfuric acids The ratio of dissolved nickel to oxygen consumption was studied for the corrosion of nickel in oxigen containing acid. In air saturated 1 N H₂SO₄ 4 electrons are accepted per molecule of oxygen (reduction to water). In air-saturated 1 N HCL only 2 electrons are reacting per molecule of oxygen (reduction to hydrogenperoxide) at the beginning of the reaction, in the course of the reaction (times greater than 2 hours) this value rises to 3 electrons per molecule of oxygen, according to a stationary hydrogenperoxide concentration of 7 · 10^?4 moles/l in both acid, however, the oxygen reduction leads to hydrogen peroxide as an intermediate product which in the presence of chloride ions is desorbed faster from the metal surface than it is reduced. with increasing chlorid concentration the corrosion rate decreases from H₂SO₄ to HCL solutions.It is proposed that this effect is due to different mechanisms for the anodic dissolution of the nickel.     

Effect of electrolyte composition on crack growth rate in pipeline steel

Electrolyte composition can strongly affect the rate of crack growth in pipe steel X70. A weakly acidic citrate buffer (pH 5.5) and a mixture of NS4 solution with a borate buffer (pH 7) were used as background solutions under static and cyclic strain, respectively. Various compounds that affect steel dissolution and hydrogen absorption rates were added to the solutions. Crack growth is accelerated in the presence of metal dissolution activators but hindered upon addition of a corrosion inhibitor. Hydrogen absorption promoters do not accelerate the crack growth at the corrosion potential.     

The effect of hydrogen peroxide on crack growth rate in X70 pipeline steel under static load

The dependence of the crack growth rate in X70 pipeline steel on the concentration of hydrogen peroxide in a citrate buffer solution (pH 5.5) is found to have a minimum. The phenomenon is explained by the effect of hydrogen peroxide on the permeation rate of hydrogen in the metal, which in turn determines the dissolution rate of iron.     

Role of polyacrylamide concentration on corrosion behavior of N80 steel in the HPAM/H2S/CO2 environment

The effect of polyacrylamide on corrosion behavior of N80 steel in the HPAM/H₂S/CO₂ environment was studied by using weight-loss and electrochemical tests to simulate the environment of production wells in polymer flooding. The morphology and composition of corrosion scales were studied by scanning electron microscopy, energy dispersive X-ray spectrometer, and X-ray photoelectron spectroscopy. The results show that as the polyacrylamide concentration increases, the uniform corrosion rate of N80 steel decreases gradually. The safe service life of N80 steel grows along with the increase of the concentration of polyacrylamide. The corrosion scales of N80 steel in the HPAM/H₂S/CO₂ environment is split into two layers, an inner layer of O-rich composed of FeCO₃ and an outer layer of S-rich consisting of FeS. Polyacrylamide adsorbs on the surface of N80 steel to form a protective network, which blocks contact between the metal and the solution and then inhibits the anodic dissolution of the metal. Moreover, the growth of polyacrylamide concentration increases the pH value of the solution and promotes the ionization of H₂S, HS⁻, and H₂CO₃ in the solution.     

Corrosion of uranium dioxide in hydrogen peroxide solutions

The corrosion behaviour of specimens cut from nuclear grade CANDU pellets has been studied electrochemically and under open-circuit corrosion conditions in hydrogen peroxide containing, slightly alkaline (pH=9.5) sodium perchlorate solution with and without added carbonate. The compositions of the electrode surfaces were determined using X-ray photoelectron spectroscopy (XPS). Three distinct ranges of behaviour are observed as a function of H₂O₂ concentration. For H₂O₂ concentrations lower than 10⁻⁴ mol/L, the UO₂ corrosion potential is directly proportional to H₂O₂ concentrations. For H₂O₂ concentrations between 10⁻⁴ and 10⁻² mol/L, the UO₂ surface appears to be redox buffered by the H₂O₂ decomposition. For H₂O₂ concentrations higher than 10⁻² mol/L, the formation of U(VI) corrosion product deposits may block H₂O₂ decomposition. Under these conditions UO₂ corrosion is driven by reaction with H₂O₂. When carbonate is present, the formation of U(VI) deposits is avoided and H₂O₂ decomposition continues to occur at high [H₂O₂]. When the pH is decreased, UO₂ dissolution is accelerated and for pH?5 uranyl peroxide deposits may form on the electrode surface. The importance of H₂O₂ decomposition at low pH (i.e. ?6) is not fully understood.     

Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in a CO2-Containing Solution

The electrochemical corrosion and stress corrosion cracking (SCC) behaviors of X70 pipeline steel in CO₂-containing solution were studied by electrochemical measurements, slow strain rate tensile tests, and surface characterization. The results found that the electrochemical corrosion of X70 steel in aerated, alkaline solution is an activation-controlled process, and a stable passivity cannot develop on steel. Corrosion rate of the steel increases with the CO₂ partial pressure. The enhanced anodic dissolution due to the additional cathodic reaction in the presence of CO₂, rather than the film-formation reaction, dominates the corrosion process. The mass-transfer step through FeCO₃ deposit is the rate-controlling step in corrosion of the steel. The susceptibility of steel to SCC and the fracture brittleness increase with the CO₂ partial pressure. The enhanced fracture brittleness is attributed to the evolution and penetration of hydrogen atoms into the steel, contributing to crack propagation. The formed deposit layer is not effective in reducing hydrogen permeation due to the loose, porous structure.     

The Effect of Oxygen on Copper Dissolution during Cathodic Polarization

The effect of oxygen on the anomalous dissolution of copper in acidic chloride media is studied. An increase in the copper corrosion rate during cathodic polarization in the potential range from –0.4 to –0.7 V is attributed to stirring of the near-electrode layer by evolving hydrogen bubbles. An addition of surface-active tetrabutylammonium iodide shifts the overpotential of hydrogen evolution and eliminates this effect. The copper dissolution rate during cathodic polarization is shown to be directly proportional to the reduction rate of dissolved oxygen. It is shown experimentally that H₂O₂ does not affect the dissolution rate of copper during cathodic polarization. The latter fact makes it possible to assume that oxygen reduction stages, which involve hydrogen peroxide, do not affect the anomalous dissolution of copper.     

Effect of ascorbic acid on hydrogen peroxide decomposition into an environmentally friendly mixture for pickling of 316L stainless steel

One of main disadvantages of using environmentally friendly chemical mixtures for pickling, is stabilization of hydrogen peroxide (H₂O₂), due to its decomposition is affected by the presence of metal ions. In previous studies, p-toluenesulfonic acid (C₇H₁₀O₄S) was used as a hydrogen peroxide stabilizer; however, benzene rings in its structure have a certain level of toxicity. In this work, ascorbic acid (C₆H₈O₆) was tested as a stabilizer agent for H₂O₂ in a pickling mixture composed by sulfuric acid (H₂SO₄) and hydrofluoric acid (HF)-H₂O₂, this mixture was tested on 316L stainless steel (SS). Decomposition of H₂O₂ in pickling solution was evaluated for different ferric ions concentration between 0 to 40 g/L and at different temperatures from 25° to 60°C. Pickling rates at 25°C for 316L SS were 26873 mg/dm² and 27799 mg/dm² using ascorbic acid and p-toluenesulfonic acid, respectively. Ascorbic acid has a positive influence on stabilization processes of H₂O₂.     

Leaching of chalcopyrite with hydrogen peroxide in hydrochloric acid solution

The aim of this work was to investigate the leaching of chalcopyrite concentrate in hydrochloric acid with hydrogen peroxide as a strong oxidizing agent. The effects of the leaching variables on metal extraction, such as stirring speed, solid-to-liquid ratio, temperature and HCl and H₂O₂ concentrations, were studied. The maximum final copper extraction of 33% was attained with 3.0 mol/L H₂O₂ in 0.5 mol/L HCl at room temperature after 180 min of the reaction. The results showed that the copper extraction was increased in the first 60 min of reaction, after which it essentially ceased due to the fast catalytic decomposition of hydrogen peroxide. Further, solid-to-liquid ratio affected the copper extraction significantly and the highest copper extraction was obtained in the most dilute suspension (i.e., S/L ratio of 1:100). The dissolution process was described by the first order kinetics equation. The apparent activation energy of 19.6 kJ/mol suggested that the dissolution process was under diffusion control. The reaction orders for HCl and H₂O₂ were established to be 0.30 and 0.53, respectively. The results of the XRD and SEM/EDS analysis of the leaching residue indicated the generation of the elemental sulphur on mineral surfaces which tended to inhibit the leaching rate.     

Leaching of blended copper slag in microwave oven

Leaching of blended slag (BS) was investigated in a microwave oven using hydrogen peroxide and acetic acid. The BS was a mixture of converter and flash furnace slag containing 51% Fe₂O₃, 3.8% CuO, and 3.2% ZnO. The important variables that influence the metal extraction yield were leaching time, liquid-solid ratio, H₂O₂ and CH₃COOH concentrations. The preferred leaching conditions were as follows: CH₃COOH concentration 4 mol/L; H₂O₂ concentration 4 mol/L; microwave power 900 W; leaching time 30 min; liquid-solid ratio 25 mL/g BS; leaching temperature 100 °C. Under these conditions, the metal extractions of 95% Cu, 1.6% Fe, and 30% Zn were obtained. The results were compared with the traditional leaching results. It is evident that microwave heating causes a reduction in the leaching time. Also, the extraction yield results indicate that selective leaching of BS can be achieved under the preferred conditions. The dissolution kinetic of BS in hydrogen peroxide with acetic acid is controlled by a shrinking unreacted core model equation. The apparent activation energy and reaction order were found to be 16.64 kJ/mol and 1.09, respectively.     

Untersuchungen über den Einfluß von Schwefelwasserstoff und Schwefeldioxyd auf die Korrosion chemisch beständiger Chrom-Nickel-Stähle in schwefelsaurer Natriumsulfatlösung

Investigations into the influence of hydrogen sulphur dioxide on the corrosion of chemically resistant chrome nickel steels in a sulphuric acid chrome nickel steels in a sulphuric acid solution of sodium sulphate By measuring the current/potential curves and determining the weight losses, the influence of H₂S and SO₂ on the corrosion of an 18/8 Cr? NI steel and of an 18/8 Cr? Ni stell with 2pCMo and 2.8pC Cu in sodium sulphate solution has been investigated. H₂S and SO₂ have the effect of shifting the rest potential towards the electronegative side, compared with a solution flushed with nitrogen, enlarging the potential range of active dissolution, and greatly increasing the dissolution, and greatly increasing the corrosion rate in the active zone. From the results of the measurements, it may be concluded that the metal dissolution is catalyzed by hydrogen sulphide ions and probably by reduction products of the sulphur dioxide. This catalyzing effect is not confined to the zone of activation overpotential but also occurs in the zone of the active plateau, the shape of which is largely determined by the migration phenomena. SO₂also has the effect of increasing the dissolution rate in the passive condition.     

The chloride corrosion of austenitic stainless steels and of an inconel alloy in hot acidic media

Open circuit corrosion testing of austenitic stainless steels, AISI types 304, 310 and 316, and of an Inconel alloy in boiling 5% NaCl solution at pH 2.5 was carried out. The influences of aeration and the introduction of Cl₂ and/or H₂S were also examined. Cl₂ accelerated corrosion, pitting and crack formation whereas H₂S had an inhibiting effect on the corrosion rates and pitting but induced hydrogen attack, which appeared in the form of blisters on the surface specimen. H₂S in the absence of oxygen resulted in the growth of corrosion product on the specimen surface, instead of dissolution, but the cracking tendency also increased due to hydrogen penetration. Addition of trisodium phosphate to the corrosive solution markedly reduced pitting and lowered the corrosion rate by approximately half. Throughout the various tests it was found that the resistance of different alloys to hot chloride corrosion was in the order 310 > 316 > 304 > Inconel.     

Effect of ferric ions in AISI 316L stainless steel pickling using an environmentally‐friendly H2SO4‐HF‐H2O2 mixture

A mixture of hydrogen peroxide, sulphuric and hydrofluoric acids has been used as pickling solution at pH 2.0 for AISI 316L austenitic stainless steel (SS). The stability of the H₂SO₄‐HF‐H₂O₂ mixture is assessed varying the ferric ions content from 0 to 40 g/L, the temperature from 25 to 60°C, and with and without stirring of the pickling solution. The AISI 316L SS pickling rate at 50°C was 2.6 and 0.2 mg/dm² day (mdd) in the absence and presence of 40 g/L ferric ions, respectively. p‐toluene sulphonic acid (PTSA) has been used as stabiliser of hydrogen peroxide.     

The corrosion kinetics of mild steel in the presence of cyanoguanidine formaldehyde resins

The corrosion inhibition efficiency of resins produced by condensation of cyanoguanidine and formaldehyde has been demonstrated for the acid corrosion of mild steel. The percentage inhibition was found to increase with resin concentration up to a limiting value of ca. 96%. The presence of resin was found to decrease both the rate of hydrogen evolution and the corrosion rate to the same degree. The activation energy of hydrogen evolution and of the overall corrosion reaction were found to be equal and characteristic of diffusion controlled processes. It is suggested that cyanoguanidine formaldehyde resins act as cathodic inhibitors of the acid corrosion of mild steel. It is concluded that the resin forms an insoluble film on the metal surface, diffusion through which is the rate determining step of the corrosion reaction. The degree of coverage of electrode surface was calculated from the shift in the cathodic Tafel lines caused by the presence of resin. The percentage inhibition and the degree of coverage were found to be higher in HCI than in H₂SO₄, for comparable resin concentrations. This is attributed to the adsorption of chloride ions on the metal surface forming oriented dipoles which enhance the adsorption of the resin.     

腐蚀疲劳过程中裂尖阳极溶解对裂纹扩展的作用

在模拟腐蚀疲劳裂尖介质中,分别用铂丝和40CrNiMo钢为辅助电极测定了在不同拉伸速率下中温回火的40CrNiMo钢的腐蚀电流密度i_(a)与应变速率、塑性应变量的关系,其结果为:利用疲劳裂纹尖端应变的弹塑性有限元计算,得到腐蚀疲劳裂尖阳极溶解引起的裂纹扩展与△K的关系,结果表明:中温回火的40CrNiMo钢在3.5％NaCl水容液中裂尖阳极溶解对腐蚀疲劳裂纹扩展的直接贡很小,阳极溶解的主要作用是影响为裂尖断裂区氢致开裂提供氢原子的阴极过程。     

Electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing hydrogen peroxide

The aim of this study is to evaluate the electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing H₂O₂ in the temperature range of 25–80 °C. The open circuit potential measurements, cathodic and anodic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the corrosion behaviour. The results provide kinetic data for reduction of hydrogen peroxide on Pt surface. The anodic polarization curves for Incoloy at different pH, temperature and H₂O₂ concentration are presented. EIS data generally confirm the polarization interpretations about the effects of various parameters. An equivalent circuit was used to fit all the acquired data.