The corrosion behaviour of SS 41 steel in formic and acetic acids

The corrosion behaviour of SS 41 steel in formic acid and acetic acid was investigated by measuring the corrosion weight loss, the polarization curve and the impedance at the steel-solution interface. It was found that the corrosion rates of the steel in formic acid and acetic acid are markedly dependent on acid concentration and temperature. The corrosion rates in acetic acid are smaller than those in formic acid. The corrosion potential E_corr against pH of formic acid and acetic acid solutions shows a linear relationship.     

Electrocatalytic behaviour of NiBi coatings for hydrogen evolution reaction in alkaline medium

The nickel-bismuth binary coatings with various chemical compositions were galvanostatically deposited on the copper electrode in view of their possible applications as electrocatalytic materials for the hydrogen evolution reaction (HER) in alkaline solution. The HER activity of coatings was tested with the help of potentiodynamic measurements and electrochemical impedance spectroscopy (EIS) technique. The electrochemical characterization was achieved by the means of cyclic voltammetry (CV). The surface morphology and surface composition of coatings were determined with scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The potentiodynamic measurements show that, the binary coatings decrease the hydrogen over potential and increase the current density values for HER. The EIS analysis confirms, the charge transfer resistances decrease and the double layer capacitance values increase for binary coatings. The EDX results in sign that the composition of binary coating changes by using coating bath. The Cu/NiBi-2 coating (Ni²⁺/Bi³⁺ is 99.71:0.29 molar ratio) is the best suitable cathode composition for the HER in alkaline media under these experimental conditions.     

Inhibitory effects of manganeous,cadmium and zinc ions on hydrogen evolution reaction and corrosion of iron in sulphuric acid solutions

The presence of metal ions (Cd²⁺, Mn²⁺, Zn²⁺), more electronegative than the cathodic potential for the hydrogen evolution reaction on iron in a 0.25M H₂SO₄ solution, inhibits the hydrogen evolution reaction and corrosion of iron. This effect has been explained as the under-potential deposition of the adatoms of these metals on iron.     

Effect of hydrogen sulphide on The corrosion behaviour of titanium

In this paper the effect of hydrogen sulphide on the electrochemical and corrosion behaviour of VT 1–0 commercial titanium has been studied in acidic solutions containing polarization and analytical methods. Neither in the presence of sulphate nor chloride ions hydrogen sulphide affected electrochemical corrosion parameters in less acidic solutions but in 1 M sulphuric and hydrochloric acid where the increase of the corrosion rate can be attributed first of all to the decrease of the hydrogen overvoltage. The interpretation of the results is based on considerations including the role of titanium hydrides formed during the processes.     

The corrosion behaviour of Al-cast iron in sulfuric acid

The polarisation behaviour of Al-cast iron has been determined in sulfuric acid at 25°C and has been compared to the behaviour of classical cast iron and commercial steel in the same environment. It was concluded from indirect electrochemical measurements (δE_corr/δpH and δlog i_corr/δpH) that the metal dissolution reaction was independent of pH under the given experimental conditions, and that b_A = 0,05 V for the three alloys. b_C changes from 0,116 V on steel to 0,305 V on classical cast iron and ∞ on Al-cast iron. The B values are respectively 0,015 V; 0,019 V and 0,024 V 0,024 V.     

The hydrogen evolution reaction on iron corroded in dilute and very dilute solutions of sulfuric acid

Permeation transients for hydrogen, generated by corrosion of iron in dilute solutions of sulfuric acid, were recorded with an improved electrochemical permeation apparatus.The mechanism of the hydrogen evolution reactions is coupled discharge hydrogen recombination for all methods of hydrogen generation, low current anodic polarization, cathodic polarization and corrosion.The experimental hydrogen transient was compared with that predicted theoretically.It is concluded that electrochemical hydrogen permeation is a sensitive tool for investigating processes on metal surfaces which are of engineering importance.     

Comparison of the corrosion behavior of copper tubes in formic acid and acetic acid environment

Carboxylic acids with different carbon chains have different corrosion behaviors on copper tubes. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) and acetic acid (CH₃COOH) were analyzed by vapor corrosion tests, electrochemical tests, contact angle examination, optical microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The corrosion process of copper tubes in the HCOOH environment is more complex than in the CH₃COOH environment and HCOOH is easy to cause “ant nest” corrosion on copper tubes. The corrosion rate is faster and the surface of the copper tube is more easily corroded in the CH₃COOH environment due to the formation of unstable and loose corrosion products, Cu(OH)(CH₃COO)₂·2H₂O. The results of the contact angle examination showed that the contact angles of HCOOH and CH₃COOH on copper tube surface were 25° and 9°, respectively, which means that CH₃COOH is more likely to be absorbed by the surface of the copper tube evenly. Differences in the wettability of these two carboxylic acids with copper tubes are the main reason for the different corrosion phenomena. The corrosion mechanisms of copper tubes in carboxylic acid are also discussed.     

The hydrogen evolution reaction on Ni-Sn alloys and intermetallics

Ni-Sn alloys containing 0%, 1.1%, 11.6%, 25.5%, 40.3%, 63.5%, 77.9%, 83.5%, 98% and 100% tin were prepared and examined regarding their activity towards the hydrogen evolution reaction in sulphuric acid solutions. The composition of these alloys and intermetallics was determined from the initial weight of the constituents used in the alloy preparation. The identification of various phases was carried out by X-ray diffraction analysis using ASTM standard microfiles. The surface composition of these alloys was determined by Auger electron spectroscopy for several typical cases, both before and after the cathodic polarization.The electrochemical measurements consisted of steady state potentiostatic polarization curves at various temperatures and potentiodynamic profiles. The electrochemical data deduced include Tafel slopes, exchange current densities, apparent heats of activation and potentiodynamic behaviour.On nickel and nickel-rich intermetallics, electrochemical desorption is indicated as the rate-determining step whereas the hydrogen evolution reaction appears to proceed by the initial dischange mechanism on tin and tin-rich alloys. Also the activity of nickel-rich intermetallics approaches that of nickel whereas the tin-rich alloys tend to exhibit activity similar to that of tin.     

The corrosion behaviour of chromium in hydrogen chloride gas and gas mixtures of hydrogen chloride and oxygen at high temperatures

A kinetic investigation of the CrHClO₂ system at 1 atm was carried out varying the oxygen content from 0 to 75 vol% at 400–800°C by the thermogravimetric method in stagnant gases and by measurements of weight loss and weight of sublimates after corrosion tests in flowing gases. In hydrogen chloride gas the corrosion rate is determined by the rates of formation and evaporation of a CrCl₂ scale: the scale was protective, to some extent, up to 600°C, but rapidly evaporated at still higher temperatures. The addition of oxygen led to suppression of corrosion loss up to about 500°C but to catastrophic corrosion at higher temperatures. The scale formed in the gas mixtures consisted mainly of Cr₂O₃ but vigorous vaporization of CrCl₂ and water occurred at the higher temperatures due to oxy-chlorination.     

The corrosion behaviour of nickel in hydrogen chloride gas and gas mixtures of hydrogen chloride and oxygen at high temperatures

A kinetic investigation of corrosion of nickel in hydrogen chloride gases containing 0–75% oxygen at 400–700°C was carried out by the thermogravimetric method. There was no great difference in the corrosion behaviour of nickel in the hydrogen chloride gas and its mixtures with oxygen because of exclusive formation of NiCl₂ scale, regardless of the gas compositions. The corrosion behaviour showed the mixed reaction mode; that is, NiCl₂ scale formation according to parabolic kinetics and NiCl₂ scale evaporation according to linear kinetics. With increasing temperature above 500°C, linear kinetics became predominant.     

The corrosion behaviour of iron in hydrogen chloride gas and gas mixtures of hydrogen chloride and oxygen at high temperatures

Catastrophic corrosion of iron by oxychlorination in hydrogen chloride gas containing 0–75 vol. % oxygen at 300–800°C has been investigated mainly by means of measurements of weight loss and the amount of sublimates. In pure hydrogen chloride gas, the corrosion behaviour was determined by the formation and sublimation of ferrous chloride. Addition of oxygen to hydrogen chloride gas greatly accelerated corrosion of iron due to the formation and sublimation of a low melting point volatile ferric chloride by oxychlorination reactions.     

Research into the corrosion behaviour of CuNi10Fe alloys in seawater

Report concerning the corrosion behaviour of CuNi10Fe in seawater, based on investigations carried out at Royal Naval College of the Royal Netherlands Navy. The testing program included exposition to flowing seawater, tests aimed at determining the erosion behaviour, electrochemical measurement of polarization behaviour, corrosion potential and polarization resistance, and electron microscopic investigations into the structure and composition of protective layers. The tests were carried out with natural and synthetic seawater in the laboratory and under conditions encountered on ships. Studies made with the electron microprobe reveal that the protective layers are of a very complex structure and that the formation of a really protecting layer requires two weeks' time. The protective action is due to concentration polarization because of the reduction of oxygen and oxidation of copper (due to concentration phenomena in pores) and to a reduction of the active surface.     

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.     

The corrosion behaviour in organic acid solutions—II. A steel electrode

The corrosion behaviour of steel in stagnant de-aerated citric and oxalic acid solutions (10^?5–10^?1M) in the pH range 2–6 was studied. It was found that the corrosion behaviour of steel in both acids was generally the same but it depended on the acid concentration and the pH value.In 10^?4–10^?1M, the corrosion rate (W) increased with the increase of acid concentration and decreased with the increase of pH value as follows:

$\text{log}\text{W = a+b}\text{log}\text{C, where b=0.485 and}\text{d}\text{log}\text{W}\text{d}\text{pH}\text{=?0.15?0.25.}$

At high concentration (10^?1 and 10^?2) and in the pH range 2–5, the steady state potential varied by 64 and 58 mV for a unit change of pH in oxalic and citric, respectively. The corrosion process was found to be cathodically controlled.In dilute solutions (10^?5–10^?3M) in the pH range of 2–5 and in all acid concentrations at pH 6, the steady state corrosion potential shifted in the negative direction with increase of acid concentration accompanied by an increase in the corrosion rate, indicating that the corrosion process became anodically controlled.     

The influence of ion implantation on the corrosion behaviour of iron in acid solution

The influence of ion implantation on the aqueous corrosion of pure iron in IN H₂SO₄ was studied. The iron was bombarded with 5 × 10¹⁵–10¹⁷ ions.cm^?2 of Ne, Ar, Cu, Pb and Au. The current density-potential curves of the implanted samples were measured and compared with that of untreated pure iron. Ne⁺ and Cu⁺ bombardments lead to a slightly higher corrosion rate in comparison with untreated iron. Pb⁺ depressed the corrosion rate by orders of magnitude, Au⁺ enhanced it by a factor of more than ten. The effect is attributed to a reduction or an increase of the activity of the electrode surface with respect to the cathodic hydrogen evolution reaction, i.e. the ion implantation influences strongly the exchange current density of the hydrogen evolution reaction. A marked influence of the implantation on the anodic behaviour of the corroding metal could also be observed.     

Interface characteristics and corrosion behaviour of oriented bulk Fe2B alloy in liquid zinc

The interface characteristics and corrosion behaviour of oriented Fe₂B in liquid zinc have been investigated. The results indicate that Fe₂B with preferential growth direction parallel to corrosion interface displays better corrosion resistance to liquid zinc. The Fe₂B/FeB phase transition occurs due to gradient of chemical potential in solid Fe₂B–liuqid zinc system. The liquid zinc corrosion is competition process of dissolution, Fe₂B/FeB transition and fracture–spalling. The fracture–spalling dominates corrosion process when preferred direction of Fe₂B is perpendicular to corrosion interface while Fe₂B/FeB transition plays a role in liquid zinc corrosion as preferred direction of Fe₂B is parallel to corrosion interface.     

An investigation on the mechanisms of ant nest corrosion of copper tube in formic acid environment

Copper tubes used in air-conditioners and refrigerators often fail due to ant nest corrosion (ANC) in formic acid environment. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) were analyzed by vapor corrosion tests, optical microscopy (OM), scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS). The effects of the surface condition on ANC of copper tube were also investigated. Results showed that ANC of copper tube was a spontaneous process. The surface integrity of copper tube surface oxide layer is not the decisive factor of ANC. ANC originated from the dissolution of the surface oxide layer in HCOOH, which exposed fresh copper matrix. ANC is a special electrochemical corrosion, where the copper matrix acts as an anode and the undissolved surface oxide layer acts as a cathode due to the potential difference. The accumulation of corrosion products consisting of Cu(HCOO)₂ and Cu₂O can produce a wedge effect and generate many microcracks until to penetrate the copper tube wall. These findings would provide a deep understanding of the corrosion behavior of copper and copper alloys.     

Theoretical study on hydrogen evolution reaction in transition metal borides

<正>Given increasing energy demands and environmental pollution,it is highly desirable to design new hydrogen evolution reaction(HER) catalysts.In this study,we have performed high throughput screening of transition-metal borides(M2B) and Janus counterparts for appealing catalysts.The simulations showcase that the Pd₂B,PdPtB,PdIrB and PdAuB possess favorable HER performance with the different chemical nature and unique asymmetry structure.To our surprise,