Indoor atmospheric corrosion of conventional weathering steels in the tropical atmosphere of Panama

One year indoor atmospheric corrosion examinations have been carried out on two conventional weathering steels for a year, at two test sites, Tocumen and Sherman Breakwater in Panama. They are environmentally classified by ISO 9223 as S₁P₀ τ ₄ and S₃P₀ τ ₅, respectively. In this humid-tropical marine climate corrosion rates are rather high, especially at Sherman Breakwater test site, mainly due to the high deposition of chloride, among other environmental conditions. Our results indicate that indoor corrosion is highly determined by the time of wetness and chloride ions. A-588 weathering steel corroded at a generally lower rate than COR-420 weathering steel. Rust characterization was performed by XRD, FTIR, and Mössbauer spectroscopy. Lepidocrocite, goethite, maghemite and akaganeite were found as corrosion products. Akaganeite is only detected when high chlorides deposition rates are obtained, and no washing effect occurs. This phase, together with maghemite, is obtained when there is greater aggressiveness in the environment.     

Atmospheric corrosion of mild steel in Oman

A systematic study has been made of the initial corrosion products which form on mild steel capons exposed near the coastal region of Oman and at some industrial areas. The phases and compositions of the products formed at different periods of exposure were examined by using Mössbauer spectroscopy (295 and 78 K) and X-ray diffraction (XRD) techniques. The results show that lepidocorcite and maghemite are early corrosion products and goethite starts to form after 2 months of metal exposure to the atmosphere. Akaganeite is an early corrosion product but it forms in marine environments only, which reflects the role of chlorine effect in the atmosphere. The 12 months coupons showed the presence of goethite, lepidocorcite and maghemite, but no akaganeite being seen in the products of one of the studied areas.     

Characterization of the corrosion products formed on mild steel in acidic medium with N-octadecylpyridinium bromide as corrosion inhibitor

The characterization of the corrosion products formed on mild steel SAE 1018 after 2 months exposure in aqueous sulfuric acid with and without corrosion inhibitor N-octadecylpyridinium bromide has been carried out by means of transmission ⁵⁷Fe Mössbauer spectroscopy and X-ray powder diffraction (XRD). The major constituent of the rust formed in this environment without corrosion inhibitor is goethite (??-FeOOH). The samples with N-octadecylpyridinium bromide contain rozenite and large amounts of melanterite in the corrosion layers.     

Kinetics and structural studies of the atmospheric corrosion of carbon steels in Panama

The corrosion of a carbon steel was studied in different atmospheres at sites in the Republic of Panama. The weight loss (corrosion penetration) suffered by the carbon steel is related to time by a bilogarithmic law. Mössbauer spectroscopy indicated the rust was composed of non-stoichiometric magnetite (Fe_3-xO₄), maghemite (γ-Fe₂O₃), goethite (α-FeOOH) of intermediate particle size, lepidocrocite (γ-FeOOH) and superparamagnetic particles. Magnetite formation is related to the alternating dry--wet cycles. Goethite is related to corrosion penetration by a saturation type of behavior, following a Langmuir type of relationship. Goethite in rust protects steel against further atmospheric corrosion.     

The corrosion products of weathering steel and pure iron in simulated wet-dry cycles

Mössbauer spectroscopy and X-ray diffraction were used to establish the composition of the rust formed on pure iron and weathering steel after exposure to several wet-dry cycles in an SO₂-polluted atmosphere. α-FeOOH poorly crystallized andquasi amorphous ferrihydrite are identified as the main corrosion products. The rust has different particle size for iron and weathering steel samples.     

Volatile corrosion inhibitor film formation on carbon steel surface and its inhibition effect on the atmospheric corrosion of carbon steel

A novel volatile corrosion inhibitor (VCI), bis-piperidiniummethyl-urea (BPMU), was developed for temporary protection of carbon steel. Its vapor corrosion inhibition property was evaluated under simulated operational conditions. Electrochemical impedance spectroscopy was applied to study the inhibition effect of BPMU on the corrosion of carbon steel with a thin stimulated atmospheric corrosion water layers. Adsorption of BPMU on carbon steel surfaces was investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results indicate that BPMU can form a protective film on the metal surface, which protects the metal against further corrosion. The structure of the protective film was suggested as one BPMU molecule chelated with one Fe atom to form a complex with two hexa-rings.     

Electrochemical synthesis of polythiophene on nickel coated mild steel and corrosion performance

Electrochemical polymerization of polythiophene (PTh) was investigated on nickel coated mild steel (MS) electrode, in LiClO₄ containing acetonitrile medium (ACN-LiClO₄). Nickel layer (1 μm thick) was deposited galvanostatically, from a proper bath solution. Then, the synthesis of PTh film was achieved in 0.1 M thiophene containing ACN-LiClO₄, by using cyclic voltammetry technique. The corrosion performances of nickel coated samples with and without polymer top coats were investigated in 3.5% NaCl solution, by using electrochemical impedance spectroscopy (EIS) and anodic polarization curves. The nickel coating behaved like a physical barrier and provided some protection to MS against corrosion. But its barrier property diminished significantly with time and failed to protect MS. It was shown that PTh top coat improved the barrier efficiency remarkably, and excellent protection efficiency was obtained against MS corrosion, for considerable exposure time in such aggressive environment.     

Mössbauer study of the corrosion behaviour of pure iron and weathering steel under a wet-dry cycle

Mossbauer spectroscopy (MBS) and X-ray diffraction (XRD) have been used to establish the composition of the rust layer formed on weathering steel and pure iron under several wet-dry cycles in a SO₂-polluted atmosphere. FeSO₃−3H₂O, FeSO₄−4H₂O, and poorly crystalline ferrihydrite were identified as the only corrosion products. The Mossbauer spectrum of FeSO₃−3H₂O is reported.     

Analysis of atmospheric corrosion products of steel and coated steel by means of scattering Mössbauer spectrometry

Wearthering steels treated with and without zinc phosphate solution were exposed to atmosphere for 15 years and rust layers produced on the steels were analysed by scattering Mössbauer spectrometry (CEMS and XMS). γ-FeOOH, fine α-FeOOH, 5Fe₂O₃·9H₂O, γ-Fe₂O₃ and Fe₃O₄ were identified to be present in the rust formed on the steel without phosphate coating. Large particles of γ-Fe₂O₃ and Fe₃O₄ formed on the uncoated steel exposed to atmosphere in a position facing north on vertical plane. The layer structure of rust was affected by the position. The thin rust layer formed on the phosphate + carylite resin coated steel was considered to consist of γ-FeOOH, fine α-FeOOH, and fine γ-Fe₂O₃.     

The corrosion of weathering steel by SO2 polluted atmospheres at its very early stages

CEMS was used in conjunction with AES to study the protective film formed on a weathering steel by exposure to a highly SO₂-polluted atmosphere. Ferrous species (sulphite) and ferric oxyhydroxides (ferrihydrite and α-FeOOH) were identified as corrosion products. From the correlation of CEMS and AES results the evolution with time of the different compounds is obtained, and a possible reaction sequence is outlined.     

Inhibition of mild steel corrosion by Morinda tinctoria leaves extract in sulphuric acid medium

The corrosion inhibition of mild steel in 0.5 M sulphuric acid by aqueous and acid extracts of leaves of Morinda tinctoria was studied using weight loss, colorimetric and electrochemical techniques. Results obtained indicate that both the extracts are effective in sulphuric acid medium and the efficiency decreases with increase in temperature. Added halide additives improve the efficiency of the inhibitor. From the thermodynamic, spectral, and surface analyses, the nature of adsorption has been found out.     

Inhibition of corrosion of commercial mild steel in presence of tetrazole derivatives in acid medium

The inhibitive influence of tetrazole derivatives namely, 1-(9¹-acridinyl)-5-(4′-aminophenyl) tetrazole, 1-(9′-acridinyl)-5-(4′-hydroxy phenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-chlorophenyl) tetrazole on the corrosion of commercial mild steel in 1 N hydrochloric acid medium was studied by weight loss method. The monolayer adsorption has been confirmed by fitting the data to the Langmuir adsorption isotherm. Weight loss studies have been carried out at 303K, 318K and 333K. Thermodynamic parameters like heat of adsorption, activation energy and free energy change have been calculated. The maximum inhibition of efficiency of tetrazole derivatives, 1-(9′-acridinyl)-5-(4′-amoinophenyl) tetrazole, 1-(9′acridinyl)-5-(4′-hydroxyphenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-Chlorphenyl) tetrazole was found to be 60.59%, 89.00% and 92.74, respectively. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Characterization of corrosion products of a carbon steel screw-nut set exposed to mountain weather conditions

In this work we present the results obtained by means of Mössbauer Spectroscopy to determine and characterize different corrosion products coming from a carbon steel screw-nut set exposed to mountain weather conditions for more than 70 years, in Las Cuevas (Mendoza–Argentina). Measurements at room temperature and 15 K were performed, detecting a great quantity of goethite but also lepidocrocite, hematite, magnetite and maghemite. This study was complemented by material characterization in terms of chemical composition, microscopic observation and X-ray diffraction analysis.     

Comparative Mössbauer and sem study of the corrosion reaction of iron and weathering steel in SO2-polluted atmospheres

A kinetic CEMS study of the early corrosion stages of iron and weathering steel in low (LAC) and very low (VLAC) SO₂-polluted atmospheres has been carried out. The morphology and sulphur content of corrosion products were examined with SEM-EDAX.     

Density functional theory and molecular dynamics simulation study on corrosion inhibition performance of mild steel by mercapto-quinoline Schiff base corrosion inhibitor

Corrosion inhibition mechanism of two mercapto-quinoline Schiff bases, eg., 3-((phenylimino)methyl)quinoline-2-thiol (PMQ) and 3-((5-methylthiazol-2-ylimino)methyl) quinoline-2-thiol (MMQT) on mild steel surface is investigated by quantum chemical calculation and molecular dynamics simulation. Quantum chemical parameters such as E_HOMO, E_LUMO, energy gap (ΔE), dipolemoment (µ), electronegativity (χ), global hardness (η) and fraction of electron transfers from the inhibitor molecule to the metallic atom surface (ΔN) have been studied to investigate their relative corrosion inhibition performance. Parameters like local reactive sites of the present molecule have been analyzed through Fukui indices. Moreover, adsorption behavior of the inhibitor molecules on Fe (1 1 0) surface have been analyzed using molecular dynamics simulation. The binding strength of the concerned inhibitor molecules on mild steel surface follows the order MMQT>PMQ, which is in good agreement with the experimentally determined inhibition efficiencies. In view of the above, our approach will be helpful for quick prediction of a potential inhibitor from a lot of similar inhibitors and subsequently in their rational designed synthesis for corrosion inhibition application following a wet chemical synthetic route.     

Inhibiting effects of some oxadiazole derivatives on the corrosion of mild steel in perchloric acid solution

The efficiency of 3,5-bis(n-pyridyl)-1,3,4-oxadiazole (n-POX, n = 1, 2, 3), as corrosion inhibitors for mild steel in 1 M perchloric acid (HClO₄) have been determined by weight loss measurements and electrochemical studies. The results show that these inhibitors revealed a good corrosion inhibition even at very low concentrations. Comparison of results among those obtained by the studied oxadiazoles shows that 3-POX was the best inhibitor. Polarisation curves indicate that n-pyridyl substituted-1,3,4-oxadiazoles are mixed type inhibitors in 1 M HClO₄. The adsorption of these inhibitors follows a Langmuir isotherm model. The electronic properties of n-POX, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).     

The inhibition of mild steel corrosion in acidic medium by 2,2′-bis(benzimidazole)

A new corrosion inhibitor, namely 2,2′-bis(benzimidazole) has been synthesised and its inhibiting action on the corrosion of mild steel in acidic bath (1 M HCl) has been investigated by various corrosion monitoring techniques, such as corrosion weight loss test and potentiodynamic polarisation. The results of the investigation show that this compounds have fairly good inhibiting properties for steel corrosion in hydrochloric acid, and is a mixed inhibitor in (1 M HCl). The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm.     

Quinoxaline derivatives as corrosion inhibitors for mild steel in hydrochloric acid medium: Electrochemical and quantum chemical studies

The corrosion inhibition potential of four quinoxaline derivatives namely, 1-[3-(4-methylphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Me-4-PQPB), 1-(3-(4-methoxyphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl)butan-1-one (Mt-4-PQPB), 1-[3-(3-methoxyphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Mt-3-PQPB) and 1-[3-(2H-1,3-benzodioxol-5-yl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Oxo-1,3-PQPB) was studied for mild steel corrosion in 1 M HCl solution using electrochemical, spectroscopic techniques and quantum chemical calculations. The results of both potentiodynamic polarization and electrochemical impedance spectroscopic studies revealed that the compounds are mixed-type inhibitors and the order of corrosion inhibition efficiency at 100 ppm is Me-4-PQPB>Mt-3-PQPB>Oxo-1,3-PQPB>Mt-4-PQPB. Fourier transform infrared (FTIR) and ultraviolet–visible (UV–vis) spectroscopic analyses confirmed the presence of chemical interactions between the inhibitors and mild steel surface. The adsorption of the inhibitor molecules on mild steel surface was found to be both physisorption and chemisorption but predominantly chemisorption. The experimental data obey Langmuir adsorption isotherm. Scanning electron microscopy studies revealed the formation of protective films of the inhibitors on mild steel surface. Quantum chemical parameters obtained from density functional theory (DFT) calculations support experimental results.     

Mössbauer investigation of the influence of the sea atmosphere on the corrosion of steel constructions in Sochi

A study of the sea atmosphere influence on the corrosion products of steel constructions near Sochi at difference distances from the sea has been made. The phases and compositions of the corrosion products formed on different sides of steel construction elements were examined by using Mössbauer spectroscopy (at 298 and 78 K). The results show that phases and composition distributions in oxide films are different on different parts of the constructions. The differences depend not only on the distance from the sea, but from their relative orientation to the sea also. The phase structure of the oxide films on different positions is identified.     

Molecular modeling study on inhibition performance of imidazolines for mild steel in CO2 corrosion

Corrosion inhibiting performance of 1-hydroxyethyl-2-heptadecylimidazoline (A) and 1-aminoethyl-2-heptadecylimidazoline (B) for mild steel was evaluated by combination of quantum chemistry calculation, molecular mechanics, and molecular dynamics simulation. The calculated results by quantum chemistry method demonstrated that frontier orbitals of A and B molecules are mainly located on imidazoline rings, and molecule B possesses higher reactivity than molecule A. The calculated results by molecular mechanics and molecular dynamics simulation presented that these two inhibitor molecules could form dense and high-coverage membranes to prevent diffusion of reactive corrosive species to metal surface. Furthermore, the adsorption energy, cohesive energy, and adsorption angle demonstrated that the binding affinity and stability of B membrane was remarkably greater than that of A, which indicated that B had better inhibition performance in CO₂ corrosion. The calculated results were well accorded with previous reported experimental results. These researches implied that molecular modeling might be an effective approach to assess inhibition performance, which has potential application in design of new inhibitors.