The inhibition action of ammonium salts of O,O′-dialkyldithiophosphoric acid on carbon dioxide corrosion of mild steel

Ammonium salts of O,O′-dialkyldithiophosphoric acids (RО)₂ Р(S) S⁻ HN⁺, were synthesized and tested as inhibitors for carbon dioxide corrosion of mild steel using weight loss, polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy methods. High inhibition efficiency has been found for all compounds (η = 70–99%) at very low concentrations (0.25–5) mg l⁻¹. Polarization curves show that the title compounds can be considered as inhibitors of the mixed type. The absorption of inhibitor molecules on the mild steel surface obeys the Langmuir isotherm. Inhibition efficiency for some ammonium salts increases with temperature. The activation energy and some thermodynamic parameters were computed.     

Gamma-radiation-induced corrosion of carbon steel in neutral and mildly basic water at 150 °C

The effect of γ-radiation on the kinetics of carbon steel corrosion has been investigated by characterizing the oxide films formed on steel coupons at 150 °C and at two pH values. Results show that continuous irradiation enhances surface oxide formation with the type of oxide formed dependant on the solution pH. For experiments at 150 °C and a [OH⁻] equivalent to that for pH_{25 °C} = 10.6, the surface oxide on carbon steel after γ-irradiation was non-porous and uniform, and no localized corrosion was observed. This oxide, however, appears to be susceptible to brittle fracture during cooling. Raman spectroscopy of the surface film indicates that it is a mixture of the phases of Fe₃O₄ and γ-Fe₂O₃. In contrast, at 150 °C with [OH⁻] equivalent to neutral pH_{25 °C}, metal dissolution is significant and the surface oxide film is very porous. Raman spectra show that this oxide film is also composed of a mixture of Fe₃O₄ and γ-Fe₂O_3. The results from this work combined with previously reported electrochemical studies of the same system as a function of pH and temperature can be used to deconvolute the effects of radiation, pH and temperature on the nature of the corrosion process.     

Novel cationic gemini surfactants as corrosion inhibitors for carbon steel pipelines

In the present investigation novel cationic gemini surfactants namely: bis(p-(N,N,N-octyldimethylammonium bromide)benzylidene)benzene-1,4-diamine (I), bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene)benzene-1,4-diamine (II), and bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene)benzene-1,4-diamine (III) were synthesized, characterized, and tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency was measured by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and weight loss methods. The obtained results showed that, the synthesized inhibitors are excellent inhibitors for carbon steel in 1 M HCl solution. The inhibition efficiency decreased in the temperature range 30-40 °C and then increased in the temperature range 40-60 °C. The prepared inhibitors act as mixed inhibitors. Thermodynamic and activation parameters were discussed. Adsorption of the synthesized inhibitors was found to follow the Langmuir’s adsorption isotherm. Mixed physical and chemical adsorption mechanism is proposed. The morphology of carbon steel samples was investigated by scanning electron microscopy (SEM).     

Corrosion inhibition of C38 steel in 1 M hydrochloric acid medium by alkaloids extract from Oxandra asbeckii plant

The inhibition effect of alkaloids extract from Oxandra asbeckii plant (OAPE) on the corrosion of C38 steel in 1 M hydrochloric acid solution has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases on increasing plant extracts concentration. Cathodic and anodic polarization curves show that OAPE is a mixed-type inhibitor. The effect of temperature on the corrosion behavior of C38 steel in 1 M HCl with and without addition of plant extract was studied in the temperature range 25–55 °C. The thermodynamic functions of dissolution and adsorption processes were calculated from experimental polarization data and the interpretation of the results are given. The adsorption of this plant extract on the C38 steel surface obeys the Langmuir adsorption isotherm. Surface analysis (Raman) was also carried out to establish the corrosion inhibitive property of this plant extract in HCl solution.     

Chemistry and melting characteristics of fireside deposits taken from boiler tubes in waste incinerators

Twenty-three tube deposits taken from seven heat-recovery boilers of municipal solid waste incinerators were examined by chemical analyses and X-ray diffraction. These deposits were measured by Differential Scanning Calorimeter (DSC) in N₂ to investigate their melting characteristics. Sixteen deposits were used to evaluate their corrosiveness to carbon steel by high-temperature corrosion test conducted at 400 °C for 20 h in 1500 ppm HCl – 300 ppm SO₂ – 7.5%O₂ – 7.5%CO₂ – 20%H₂O – N₂. Total heat of endothermic reactions of the deposits taking place between 200 and 400 °C can be related to the corrosion rate of carbon steel at 400 °C. Corrosion initiated at temperatures when the deposits started to melt, became severe when fused salt constituents increased, and alleviated when the majority of the deposits became fused. The corrosion can be interpreted as fused salt corrosion caused by chloride and sulfate salts.     

Inhibition effects of some Schiff’s bases on the corrosion of mild steel in hydrochloric acid solution

The corrosion inhibition effect of 4-{[(1Z)-(2-chloroquinolin-3-yl)methylene]amino} phenol (CAP), N-[(1Z)-(2-chloroquinolin-yl)methylene]-N-(4-methoxyphenyl)amine (CMPA) and N-[(1E)-(2-chloroquinolin-3-yl)methylene]-N-(4-nitrophenyl)amine (CNPA) on mild steel in 1.0 M HCl has been investigated using mass loss, polarization and electrochemical impedance techniques at 300 K. The inhibition efficiencies increased with increase in inhibitors concentration. Polarization studies showed that the inhibitors are of predominantly cathodic character. Among the three compounds studied, CAP exhibited the best performance giving more than 97% IE. Some samples of mild steel were examined by SEM. All the inhibitors were found to adsorb on the mild steel surface according to the Langmuir adsorption isotherm.     

Effect of antimony on the corrosion behavior of low-alloy steel for flue gas desulfurization system

The alloying effect of Sb in a new low-alloy steel for the purpose of FGD materials was investigated by potentiodynamic polarization, linear polarization resistance measurement, electrochemical impedance spectroscopy (EIS) and weight loss measurements in an aggressive solution of 16.9 vol.% H₂SO₄ + 0.35 vol.% HCl (modified green death solution) at 60 °C, pH −0.3. All measurements confirmed the marked improvement in the corrosion behavior of the low-alloy steel via the addition of a small amount of Sb, particularly for the 0.10Sb steel. Pitting corrosion was detected by scanning electron microscopy (SEM) on the surface of blank steel and 0.05Sb steel, but not 0.10Sb steel, after weight loss measurements. X-ray photoelectron spectroscopy (XPS) analysis of the corroded surfaces after EIS and linear polarization measurements showed that the decrease in corrosion rates was due to the formation of a protective Sb₂O₅ oxide film on the surface of the Sb-containing steels. Moreover, the addition of 0.10% Sb stimulated the development of high corrosion inhibiting, Cu-containing compounds which further inhibited the anodic and cathodic reactions.     

Corrosion behaviour of micro-plasma arc welded stainless steels in H3PO4 under flowing conditions at different temperatures

This paper studies the general corrosion behaviour of the micro-plasma arc welded AISI 316L stainless steel in phosphoric acid at different temperatures (25–60 °C) and at a Reynolds number of 1456. Galvanic corrosion has been studied using zero-resistance ammeter (ZRA) measurements and polarization curves (by the mixed potential theory). Results show that the microstructure of the stainless steel is modified due to the micro-plasma arc welding procedure. Coupled current density values obtained from polarization curves increase with temperature. ZRA tests present the highest i_G values at 60 °C; however, the values are very close to zero for all the temperatures studied. This is in agreement with the low value of the compatibility limit and of the parameter which evaluates the importance of the galvanic phenomenon. Both techniques present the most positive potentials at the highest temperature. This study reveals that micro-plasma arc welded AISI 316L stainless steels are appropriated working in the studied H₃PO₄ media from a corrosion point of view for all the temperatures analysed.     

Corrosion behavior of alumina ceramics in aqueous HCl and H2SO4 solutions

The corrosion behavior of cold isostatically pressed (CIP) high purity alumina ceramics in aqueous HCl and H₂SO₄ solutions with various concentrations has been studied simultaneously at room temperature (25 °C). Corrosion tests were also performed with 0.65 mol/l HCl and 0.37 mol/l H₂SO₄ solutions at 40, 55 and 70 °C for 48 h. Chemical stability was monitored by determining the amount of Al³⁺, Mg²⁺, Ca²⁺, Na⁺ Si⁴⁺ and Fe³⁺ ions eluted in different concentrations of HCl and H₂SO₄ solutions by means of atomic absorption spectrometry (AAS). By increasing the concentration from 0.37 to 6.5 mol/l, it was notified that the corrosion susceptibility in HCl and H₂SO₄ solutions for the CIP alumina specimens at room temperature decreases.     

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine

The behavior of the Schiff base N,N′-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1 mol L⁻¹ HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the inhibitors studied. The results obtained in the presence of Salen were similar to those obtained in the presence of the salicylaldehyde and ethylenediamine mixture, showing that in acid medium the Salen molecule undergoes hydrolysis, regenerating its precursor molecules.     

Effect of carbon on corrosion and passivation of iron in hot concentrated NaOH solution in relation to caustic stress corrosion cracking

Quenched Fe-C materials with up to 0.875 wt.% C were examined in 8.5 M NaOH at 100 °C to better understand the effect of carbon on caustic stress corrosion cracking (SCC) of plain steels. Carbon at contents up to about 0.23 wt.% C accelerated anodic dissolution of iron, whereas at high contents it hindered corrosion and promoted the formation of magnetite. It is suggested that carbon particles on the corroding surface form confined regions with an increased concentration of H⁺ and HFeO₂⁻, thereby favouring the formation of Fe₃O₄. Intergranular SCC can be explained by preferred anodic dissolution of grain boundary material enriched in carbon.     

Corrosion behavior of iron-based alloys in the LiBr + ethylene glycol + H2O mixture

The corrosion resistance of 1018 carbon steel, 304 and 316 type stainless steels in the LiBr (55 wt.%) + ethylene glycol + H₂O mixture at 25, 50 and 80 °C has been studied using electrochemical techniques which included potentiodynamic polarization curves, electrochemical noise and electrochemical impedance spectroscopy techniques. Results showed that, at all tested temperature, the three steels exhibited an active-passive behavior. Carbon steel showed the highest corrosion rate, since both the passive and corrosion current density values were between two and four orders of magnitude higher than those found for both stainless steels. Similarly, the most active pitting potential values was for 1018 carbon steel. For 1018 carbon steel, the corrosion process was under a mixed diffusion and charge transfer at 25 °C, whereas at 50 and 80 °C a pure diffusion controlled process could be observed. For 316 type stainless steel, at 25 and 50 °C a species adsorption controlled process was observed, whereas at 80 °C a diffusion controlled mechanism was present. Additionally, at 25 °C, the three steels were more susceptible to uniform type of corrosion, whereas at 50 and 80 °C they were very susceptible to localized type of corrosion.     

Fabrication of continuous mesoporous organic–inorganic nanocomposite films for corrosion protection of stainless steel in PEM fuel cells

The organic–inorganic composite film was deposited on the 304 stainless steel as bipolar plate material for proton exchange membrane fuel cells by spin-coating method. As shown by XRD, N₂ adsorption–desorption and TEM, the composite films exhibit ordered mesoporous structures. The corrosion tests in 0.5 M H₂SO₄ system displayed that, compared with 304SS, the composite films made corrosion potential shifted to positive direction by 250–1000 mV (SCE) and corrosion current decreased by 1–3 orders of magnitude. Wherein, the C-50–60% composite film showed the optimal protective performance, its corresponding potentiostatic polarization process was extremely stable in the simulated fuel cells environment.     

Effect of 4-(N,N-diethylamino)benzaldehyde thiosemicarbazone on the corrosion of aged 18 Ni 250 grade maraging steel in phosphoric acid solution

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone (DEABT) was studied for its corrosion inhibition property on the corrosion of aged 18 Ni 250 grade maraging steel in 0.67 M phosphoric acid at 30–50 °C by potentiodynamic polarization, EIS and weight loss techniques. Inhibition efficiency of DEABT was found to increase with the increase in DEABT concentration and decrease with the increase in temperature. The activation energy E_a and other thermodynamic parameters (Δ, Δ, Δ) have been evaluated and discussed. The adsorption of DEABT on aged maraging steel surface obeys the Langmuir adsorption isotherm model and the inhibitor showed mixed type inhibition behavior.     

Corrosion inhibition of mild steel in sodium chloride solution by some zinc complexes

The corrosion inhibitive effect of zinc acetate, zinc acetylacetonate and zinc gluconate on the mild steel immersed in 3.5% NaCl solution was evaluated by electrochemical impedance spectroscopy (EIS). The results revealed superiority of zinc gluconate whilst zinc acetate showed inferior corrosion inhibition. The surface of the samples exposed to the inhibited solutions was analyzed using XRD and SEM techniques. The pH measurement of the test solutions before and after corrosion, also before and after addition of Fe⁺² and Fe⁺³ revealed that the superior inhibition of zinc gluconate is related to formation of insoluble corrosion products on the mild steel surface.     

Corrosion of carbon steel C1010 in the presence of iron oxidizing bacteria Acidithiobacillus ferrooxidans

In this study, corrosion behaviors of carbon steel C1010 in the presence of an acidophilic, iron-oxidizing bacterial species Acidithiobacillus ferrooxidans were examined. Results showed that A. ferrooxidans cells, with or without attaching to C1010 steel, accelerated its corrosion at a rate of 3–6× those of acidic water, at a pH of 2, without cells. A. ferrooxidans oxidized Fe²⁺ to Fe³⁺ as an energy source and the produced Fe³⁺ rapidly oxidized Fe⁰ to Fe²⁺ was proposed and verified as the reason. In addition, severe pitting corrosion was found on the C1010 steel surface in solutions containing A. ferrooxidans cells.     

Corrosion properties of active screen plasma nitrided 316 austenitic stainless steel

AISI 316 austenitic stainless steel has been plasma nitrided using the active screen plasma nitriding (ASPN) technique. Corrosion properties of the untreated and AS plasma nitrided 316 steel have been evaluated using various techniques, including qualitative evaluation after etching in 50%HCl + 25%HNO₃ + 25%H₂O, weight loss measurement after immersion in 10% HCl, and anodic polarisation tests in 3.5% NaCl solution. The results showed that the untreated 316 stainless steel suffered severe localised pitting and crevice corrosion under the testing conditions. AS plasma nitriding at low temperature (420 °C) produced a single phase nitrided layer of nitrogen expanded austenite (S-phase), which considerably improved the corrosion properties of the 316 austenitic stainless steel. In contrast, AS plasma nitriding at a high temperature (500 °C) resulted in chromium nitride precipitation so that the bulk of the nitrided case had very poor corrosion resistance. However, a thin deposition layer on top of the nitrided case, which seems to be unique to AS plasma nitriding, could have alleviated the corrosion attack of the higher temperature nitrided 316 steel.     

A novel Schiff base-based cationic gemini surfactants: Synthesis and effect on corrosion inhibition of carbon steel in hydrochloric acid solution

The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1 M hydrochloric acid have been investigated at 25 °C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that compound 14-S-14 is the best inhibitor with an efficiency of 97.75% at 5 × 10⁻³ M additive concentration. Generally, the inhibition efficiency increased with increase of the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R_ct, and double-layer capacitance, C_dl) were indicative of adsorption of 14-S-14 on the metal surface, leading to the formation of a protective film. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The free energy of adsorption processes were calculated and discussed. The surface parameters of each synthesized surfactant were calculated from its surface tension including the critical micelle concentration (CMC), maximum surface excess (Γ_max) and the minimum surface area (A_min). The free energies of micellization (ΔG^o_mic) were calculated. The surface morphology of carbon steel sample was investigated by scanning electron microscopy (SEM).     

Effect of annealing temperature on the corrosion behavior of duplex stainless steel studied by in situ techniques

The effects of the annealing temperature on the microstructure and the corrosion behavior of duplex stainless steel 2507 were investigated by means of magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The SEM results indicated that the volume fraction of the austenite phase decreased with the increased annealing temperature. SKPFM/MFM measurements conducted in air at the room temperature and an ambient relative humidity of about 25% showed a higher Volta potential of the paramagnetic austenite than that of the ferromagnetic ferrite. The in situ AFM observation in a hydrochloric acid solution provided solid evidence that corrosion preferentially occurred in the ferrite phase. The sample annealed at 1100 °C exhibited a greater Volta potential difference between the ferrite and austenite and a higher corrosion rate in the ferrite, while that annealed at 1150 °C had a smaller Volta potential difference and a lower corrosion rate. The relative nobility and microstructure change of two phases, as well as their corrosion behavior, can be explained by the effect of the composition of alloying elements.     

Hydrogen gas production during corrosion of copper by water

This paper considers the corrosion of copper in water by: (1) short term, open system weight measurements and (2) long term, closed system immersion in distilled water (13,800 h) without O₂ at 21–55 °C. In the latter experiments, the hydrogen gas pressure is measured above the immersed copper and approaches ∼10⁻³ bar at equilibrium. This pressure is mostly due to copper corrosion and greatly exceeds that in ambient air. Accordingly, this measured hydrogen pressure from copper corrosion increases with temperature and has the same dependency as the concentration of OH⁻ in the ion product [OH⁻] [H⁺].