Corrosion behaviour of carbon steel in different concentrations of HCl solutions containing H2S at 90 °C

The corrosion behavior of SAE-1020 carbon steel in H₂S-containing solutions with different concentration of HCl at 90 °C was investigated by weight loss, electrochemical measurements, SEM and XRD analysis. The results showed that the corrosion rate of carbon steel increased with increasing HCl concentration. Uniform corrosion was found on the carbon steel surface in H₂S + HCl solutions, while corrosion cavities were observed in the solution only containing H₂S. The ratio of Faradaic process of total corrosion process increased with the increase of HCl concentration. The corrosion products were solely composed of mackinawite in the H₂S-containing solutions with or without HCl.     

The influence of CO2, AlCl3 · 6H2O, MgCl2 · 6H2O, Na2SO4 and NaCl on the atmospheric corrosion of aluminum

The influence of salt deposits on the atmospheric corrosion of high purity Al (99.999%) was studied in the laboratory. Four chloride and sulfate-containing salts, NaCl, Na₂SO₄, AlCl₃ · 6H₂O and MgCl₂ · 6H₂O were investigated. The samples were exposed to purified humid air with careful control of the relative humidity (95%), temperature (22.0 °C), and air flow. The concentration of CO₂ was 350 ppm or <1 ppm and the exposure time was four weeks. Under the experimental conditions all four salts formed aqueous solutions on the metal surface. Mass gain and metal loss results are reported. The corroded surfaces were studied by ESEM, OM, AES and FEG/SEM equipped with EDX. The corrosion products were analyzed by gravimetry, IC and grazing incidence XRD. In the absence of CO₂, the corrosivity of the chloride salts studied increases in the order MgCl₂ · 6H₂O < AlCl₃ · 6H₂O < NaCl. Sodium chloride is very corrosive in this environment because the sodium ion supports the development of high pH in the cathodic areas, resulting in alkaline dissolution of the alumina passive film and rapid general corrosion. The low corrosivity of MgCl₂ · 6H₂O is explained by the inability of Mg²⁺ to support high pH values in the cathodic areas. In the presence of carbon dioxide, the corrosion induced by the salts studied exhibit similar rates. Carbon dioxide strongly inhibits aluminum corrosion in the presence of AlCl₃ · 6H₂O and especially, NaCl, while it is slightly corrosive in the presence of MgCl₂ · 6H₂O. The corrosion effects of CO₂ are explained in terms of its acidic properties and by the precipitation of carbonates. In the absence of CO₂, Na₂SO₄ is less corrosive than NaCl. This is explained by the lower solubility of aluminum hydroxy sulfates in comparison to the chlorides. The average corrosion rate in the presence of CO₂ is the same for both salts. The main difference is that sulfate is less efficient than chloride in causing pitting of aluminum in neutral or acidic media.     

Atmospheric corrosion of carbon steel in Colombia

The corrosion behaviour of carbon steel at six test sites in Colombia and its relationship with exposure time and environmental characteristics of each site were investigated. The corrosion products were characterized by XRD, SEM and EDS. It was found that in Barranquilla, the most aggressive site, corrosion depends mainly on chlorides. Furthermore, in the more aggressive environments there was a greater tendency to formation of protective corrosion products. Lepidocrocite and goethite were found as major constituents of rust. A structure not reported in the literature was found, corresponding to strings of several hundred micrometers long and consisting of lepidocrocite plates.     

Inhibition effect of 6-benzylaminopurine on the corrosion of cold rolled steel in H2SO4 solution

The inhibition effect of 6-benzylaminopurine (BAP) on the corrosion of cold rolled steel (CRS) in 1.0-7.0 M H₂SO₄ at 25-50 °C was studied by weight loss and potentiodynamic polarization methods. Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) were used to characterize the CRS surface. The results showed that BAP was a good inhibitor in 1.0 M H₂SO₄, and the adsorption of BAP obeyed the Temkin adsorption isotherm. Polarization curves showed that BAP acted as a mixed-type inhibitor in sulfuric acid. Depending on the results, the inhibitive mechanism was proposed.     

Erosion resistance of CO2 corrosion scales formed on API P110 carbon steel

The erosion resistance of CO₂ corrosion scales formed on carbon steel was investigated in water–sand two-phase flow utilizing weight loss test, scanning electron microscopy, and X-ray diffraction. The effects of CO₂ partial pressure, stirring speed, test time, and grain size on the erosion resistance of the scales were analysed. Results show that several characteristics of CO₂ corrosion scales are key factors affecting erosion resistance. Cubic polynomials are used to fit the erosion rate data, and effectively evaluate the ability of CO₂ corrosion scales to resist erosion. An erosion mechanism, based on fluid dynamics and CO₂ corrosion scales characteristics, is discussed.     

Hot corrosion behaviour of Yb2Zr2O7 ceramic coated with V2O5 at temperatures of 600-800 °C in air

To better understand the hot corrosion behaviour of Yb₂Zr₂O₇ ceramic in molten V₂O₅, hot corrosion experiments were performed in a temperature range of 600-800 °C in air. Different reaction products of ZrV₂O₇, YbVO₄ and m-ZrO₂ were identified depending upon the hot corrosion conditions, for example, ZrV₂O₇ and YbVO₄ at 600 °C for 2 h and 8 h; ZrV₂O₇, m-ZrO₂ and YbVO₄ at 700 °C for 2 h; m-ZrO₂ and YbVO₄ either at 800 °C for 2 h or at 700-800 °C for 8 h. The hot corrosion reaction mechanisms were further discussed based on the thermal instability of ZrV₂O₇ at elevated temperatures.     

Oxidation of Cr2AlC at 1300 °C in air

High purity, dense Cr₂AlC compounds were synthesized via a powder metallurgical route, and their oxidation behavior was investigated at 1300 °C in air for up to 336 h. A thin external oxide layer formed, which consisted primarily of not Cr₂O₃ but Al₂O₃. Since Al was consumed to produce the Al₂O₃, Al-depletion and Cr-enrichment occurred underneath the Al₂O₃ layer. This led to the formation of a Cr₇C₃ layer containing voids. These grew during oxidation, eventually destroying the Cr₇C₃ layer formed on the unoxidized Cr₂AlC matrix.     

Synergistic effect of halide ions on improving corrosion inhibition behaviour of benzisothiozole-3-piperizine hydrochloride on mild steel in 0.5 M H2SO4 medium

The synergistic effect of iodide ions and benzisothiozole-3-piperizine hydrochloride (BITP) on corrosion inhibition of mild steel in 0.5 M H₂SO₄ solution has been studied by both chemical and electrochemical methods. The corrosion performance of BITP in 1.0 M HCl and 0.5 M H₂SO₄ media was examined and compared. The adsorption of BITP and its combination with iodide ions on mild steel surface followed Langmuir adsorption isotherm via chemisorption mechanism. The calculated values of synergism parameter (S_θ) were found to be greater than unity. This result clearly showed the existence of synergism between iodide ions and BITP molecules.     

Synergistic inhibition effect of rare earth cerium(IV) ion and 3,4-dihydroxybenzaldehye on the corrosion of cold rolled steel in H2SO4 solution

The synergistic inhibition effect of rare earth cerium(IV) ion and 3,4-dihydroxybenzaldehye (DHBA) on corrosion of cold rolled steel (CRS) in H₂SO₄ solution was first investigated by weight loss and potentiodynamic polarization methods. Effects of inhibitor concentration, temperature, immersion time and acid concentration on synergism are discussed in detail. The results reveal that DHBA has moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. For the cerium(IV) ion, it has negligible effect. However, incorporation of Ce⁴⁺ with DHBA improves the inhibition performance significantly, and produces strong synergistic inhibition effect.     

Synergistic inhibition effect of rare earth cerium(IV) ion and anionic surfactant on the corrosion of cold rolled steel in H2SO4 solution

The synergistic inhibition effect of rare earth cerium(IV) ion and anionic surfactant of sodium oleate (C₁₇H₃₃-COONa, SO) on the corrosion of cold rolled steel (CRS) in H₂SO₄ solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that SO had a moderate inhibitive effect, and the adsorption of SO obeyed the Freundlich adsorption isotherm. For the cerium(IV) ion, it had a negligible effect. However, incorporation of Ce⁴⁺ with SO significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed.     

Effect of heat treatment on H2S corrosion of a micro-alloyed C–Mn steel

The H₂S corrosion resistance of a C–Mn pipeline steel with three different microstructures has been evaluated using electrochemical techniques with a 3% wt. NaCl solution at 50 °C. Microstructures included martensite, ferrite, and ferrite + bainite. Electrochemical techniques included potenthiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and electrochemical noise (EN) measurements. Most of the tests lasted 24 h. All techniques showed that the highest corrosion rate corresponded to the steel with a martensitic microstructure; up to one order of magnitude higher than the corrosion rate for steels with a ferritic + bainitiic microstructure, whereas the steel with the ferritic microstructure showed the lowest corrosion rate. EIS tests showed that the corrosion process was under charge transfer control, whereas EN results indicated that the three steels exhibited a clear tendency towards a localized type of corrosion. However, for longer immersion times, the steel with a martensitic microstructure tended to exhibit a mixture of uniform and localized attack. Results were discussed in terms of grain size, grain boundary energy, amount and distribution of particles found in each steel.     

Synergism between red tetrazolium and uracil on the corrosion of cold rolled steel in H2SO4 solution

The synergism between red tetrazolium (RT) and uracil (Ur) on the corrosion of cold rolled steel (CRS) in H₂SO₄ solution is first investigated by weight loss, potentiodynamic polarization, and atomic force microscope (AFM). Effects of inhibitor concentration (25-500 mg l⁻¹), temperature (20-50 °C), and acid concentration (1.0-5.0 M) on synergism are discussed systematically. The results reveal that RT has a moderate inhibitive effect, and its adsorption obeys the Freundlich adsorption isotherm. For Ur, it has a poor effect. However, incorporation of RT with Ur significantly improves the inhibition performance, and produces synergistic inhibition effect.     

In situ synchrotron X-ray diffraction study of surface scale formation during CO2 corrosion of carbon steel at temperatures up to 90 °C

In situ synchrotron X-ray diffraction was used to follow the formation of corrosion product scales on carbon steel in CO₂ saturated brine at temperatures from 40 to 90 °C. The corrosion process was accelerated by applying a small anodic current, and in selected tests a scale inhibitor, amino trimethylene phosphonic acid (ATMPA), was added. Siderite was identified as the major phase in the scale formed in all conditions. With increasing temperature, the scale formation rate increased, while the scale thickness and crystallite size decreased. Above 60 °C, the scale became increasingly protective. The scale thickness and crystallite size decreased with increasing ATMPA concentration.     

Three pyrazine derivatives as corrosion inhibitors for steel in 1.0 M H2SO4 solution

The inhibition effect of three pyrazine derivatives of 2-methylpyrazine (MP), 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0 M H₂SO₄ solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that all pyrazine compounds are good inhibitors, and inhibition efficiency follows the order: ABP > AP > MP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. For all these pyrazine derivatives, they act as mixed-type inhibitors. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

Synergistic inhibition effect of 6-benzylaminopurine and iodide ion on the corrosion of cold rolled steel in H3PO4 solution

The synergistic inhibition effect of 6-benzylaminopurine (BAP) and iodide ion (I⁻) on the corrosion of cold rolled steel (CRS) in 1.0 M H₃PO₄ solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that BAP has a moderate inhibitive effect. However, incorporation of BAP with I⁻ improves the inhibition performance significantly. The adsorption of BAP in the absence and presence of I⁻ obeys Langmuir adsorption isotherm. BAP and BAP/I⁻ mixture act as mixed-type inhibitors. A probable synergism mechanism is proposed.     

Corrosion of N80 carbon steel in oil field formation water containing CO2 in the absence and presence of acetic acid

Corrosion behaviour of N80 carbon steel in formation water containing CO₂ was studied by polarization curve technique, electrochemical impedance spectroscopy, weight loss test, scanning electron microscope, and X-ray diffraction. Effects of temperature and acetic acid concentration on the corrosion behaviour of N80 carbon steel were discussed. The results showed that increasing temperature not only enhanced the dissolution of steel substrate, but also promoted the precipitation of FeCO₃, the addition of acetic acid enhanced localized corrosion attack on N80 carbon steel. FeCO₃ was the main corrosion product. And there was a transition region between CO₂ corrosion control and HAc corrosion control.     

KCl-induced high temperature corrosion of the austenitic Fe-Cr-Ni alloys 304L and Sanicro 28 at 600 °C

The influence of KCl(s) on the high temperature oxidation of the austenitic alloys 304L and Sanicro 28 at 600 °C in O₂ + H₂O environment is reported. 0.10 mg/cm² KCl(s) was added before exposure. The samples are investigated by grazing angle XRD, SEM/EDX, and AES. In the absence of KCl, both alloys show protective behaviour in dry O₂. In O₂ + H₂O environment, alloy 304L suffers local breakaway corrosion while Sanicro 28 still shows protective behaviour. The oxidation of both alloys is strongly accelerated by KCl. KCl reacts with chromium in the normally protective corundum-type oxide, forming K₂CrO₄. This depletes the scale in chromia and leads to the formation of a non-protective, iron-rich scale. The significance of KCl-induced corrosion in real applications is discussed and the oxidation behaviour of the two steels is compared.     

H2S and O2 influence on the corrosion of carbon steel immersed in a solution containing 3 M diethanolamine

Aqueous solutions with 3 mol L⁻¹ (M) diethanolamine (DEA) concentration are extensively used in the gas processing industry to remove acid gases. However, the degradation of the DEA and the formation of heat-stable salts (HSS) lead to severe corrosion problems. Even worse, equipment corrosion can be magnified by the unavoidable presence of sulphide acid and dissolved oxygen as a result of hydrocarbon (natural gases and crude oil) processing. The aim of this work is to study the combined corrosion effects of DEA, sulphide acid and oxygen on carbon steel. Electrochemical methods revealed that in the 3 M DEA medium without oxygen, corrosion processes are modulated by adsorbed DEA film formation. Furthermore, it was shown that the addition of oxygen and 15 × 10⁻³ mol L⁻¹ (15 mM) H₂S produced the formation of an adherent film on the carbon steel surface. Chemical analyses by EDAX revealed a homogeneous film of corrosion products composed of iron oxide and sulphide formed in DEA solution containing O₂ and H₂S, respectively. Equivalent circuits were used to estimate the parameters associated with ion diffusion through the formed corrosion films. The results showed that the presence of H₂S induced the formation of thin iron sulphide films that provide protective properties to the metal. It is concluded that the presence of oxygen in a sweetening plant should be avoided as DEA degradation can be produced with the subsequent decrease in chelating process efficiency and the increase in corrosion problems.     

Experimental and theoretical calculations on corrosion inhibition of steel in 1 M H2SO4 by crown type polyethers

The corrosion inhibitive efficiencies of two crown type polyethers, namely dibenzo-bis-imino crown ether (C-1) and dibenzo-diaza crown ether (C-2), which are macrocyclic Schiff base and its reduced form (macrocyclic amine), respectively, for the steel in 1 M H₂SO₄ have been investigated by Tafel extrapolation and linear polarization methods. Corrosion and adsorption isotherm parameters were determined from current-potential curves. The studies show that C-1 and C-2 inhibit the corrosion of the steel in H₂SO₄ solution. Semiempirical AM1 method was used for theoretical calculations. The obtained results of these calculations for the compounds were found to be consistent with the experimental findings.     

Alizarin violet 3B as a novel corrosion inhibitor for steel in HCl, H2SO4 solutions

The inhibition effect of alizarin violet 3B (AV3B) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl and 0.5 M H₂SO₄ solutions was investigated for the first time by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that AV3B is a good inhibitor, and exhibits more efficient in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of AV3B on CRS surface obeys Langmuir adsorption isotherm in both acids. Polarization curves reveal that AV3B acts as a mixed-type inhibitor.