Schiff’s base of pyridyl substituted triazoles as new and effective corrosion inhibitors for mild steel in hydrochloric acid solution

Three Schiff’s bases namely (3-phenylallylidene) amino-5-(pyridine-4-yl)-4H-1,2,4-triazole-3-thiol (SB-1), 3-mercapto-5 (pyridine-4-yl)-4H-1,2,4-triazole-4-yl) imino) methyl) phenol (SB-2) and (4-nitrobenzylidene) amino)-5-(pyridine-4-yl)-4H-1,2,4-triazole-3-thiol (SB-3) were synthesized and investigated as corrosion inhibitors for mild steel (MS) in 1 M HCl. SB-1 exhibited best inhibition performance (96.6 η%) at 150 mg L⁻¹. The studied inhibitors follow Langmuir adsorption isotherm. Potentiodynamic polarization data suggests mixed-mode of corrosion inhibition. The effect of molecular structure on inhibition efficiency was investigated by theoretical calculations using density function theory (DFT) methods. Surface analysis supports the formation of a protective inhibitor film on the mild steel surface.     

Effect of the temperature of cerium nitrate–NaCl solution on corrosion inhibition of mild steel

In this study, the effect of temperature on corrosion inhibition is studied in the absence and presence of an optimal concentration of cerium nitrate (600 mg/L) as an inhibitor of mild steel in sodium chloride. Corrosion tests are carried out through electrochemical techniques such as impedance spectroscopy and d.c. polarization measurements. The surface morphology of the films is investigated by optical microscopy, white-light interferometry, and scanning electronic microscopy, coupled with energy-dispersive spectroscopy analysis for chemical composition. The results obtained show that the activation energy for the corrosion inhibition process to occur increases in the presence of a cerium nitrate inhibitor. However, the corrosion resistance of mild steel is somewhat lost upon increasing the solution temperature up to 55°C, which leads to more cracked films. The enthalpy and entropy values suggest a mixed mechanism of chemisorption and physisorption inhibition, with a major dominance of physisorption control.     

A comparative study of corrosion inhibition of steel and stainless steel in hydrochloric acid by N,N,N′,N′-tetramethyl-p-phenylenediamine

Protection of Metals and Physical Chemistry of Surfaces - The corrosion of mild steel (MS) and AISI type 321 stainless steel (AISI 321) in 1 M HCl solution and the inhibitive mechanism of...     

Corrosion inhibition of gatifloxacin on mild steel in 3% HCL solution北大核心CSCD

The inhibition effect of gatifloxacin on the corrosion of mild steel in 3%HCl solution was investigated by means of mass loss measurements and electrochemical measurements. The surface morphology of the steel after corrosion was studied by scanning electron microscope (SEM). The results demonstrated that the highest inhibition efficiency of gatifloxacin reached 95.6% for a dose of gatifloxacin 700 mg/L. Gatifloxacin acted as a mixed-type inhibitor, the cathodic and anodic processes of corrosion were suppressed. Thermodynamic parameters were acquired from data of weight loss at different experimental temperatures, which suggested that the adsorption of gatifloxacin on metal surface obeyed Langmuir adsorption isotherm model. The adsorption processes were exothermic, and belong to chemisorption and physisorption. The entropy of adsorption processes increased. © 2016, Corrosion Science and Protection Technology. All rights reserved.     

The corrosion inhibition effect of phytic acid on 20SiMn steel in saturated Ca(OH)2 solution with 1 mol L−1 NaCl

A wise strategy to hinder the degradation of the steel rebar in concrete is finding a corrosion inhibitor to resist pitting corrosion at passive state as well as the general dissolution at active dissolution state. In this paper, the corrosion inhibition effect of phytic acid (IP6) on 20SiMn steel was investigated in the simulated concrete solution with chlorides, Sat.Ca(OH)2+1 mol/L NaCl(pH=12.9), by electrochemical methods and surface analysis techniques. The results show that IP6 could prolong the incubation time of 20SiMn steel from passive to pitting corrosion and enhance the charge-transfer resistance to a certain extent with the inhibition efficiency of around 30~50%. This is ascribed to the preferential adsorption of IP6 over chloride ion on the passive film through PO4 functional groups, which lead to the formation of a compact chelation film.     

Stress—corrosion cracking of austenitic stainless steel in hydrochloric acid media at room temperature

Stress—corrosion cracking of solution quenched, type 304, stainless steel can occur at room temperature in HCl solutions ranging between 5·10^?1M and 1M HCl. The cracking observed in HCl solutions is similar to that previously observed in H₂SO₄ + NaCl and HClO₄ + NaCl solutions. Cracking occurs at ? 0·200 V (NHE), in the active potential region, it is under cathodic control, and it develops in conditions under which the corrosion rate of the external surface area is more or less constant and independent of the HCl concentration, in the range 10^?1 M?1 M HCl. At higher HCl concentrations, corrosion rates increase and uneven, general corrosion occurs instead of cracking. The development of pitting and stress—corrosion cracking under active conditions precludes the conclusion that active—passive cells always play a role in localized corrosion and, in particular, in stress—corrosion cracking. Under these conditions, it has been shown that sensitized and non-sensitized specimens behave similarly (giving rise in both cases to transgranular cracking); active—passive cells, due to chromium depletion at the grain boundaries, are not involved. Active—passive corrosion mechanisms can however arise at more noble potentials (0·100?0·200 V NHE), as in the case of HClH₂O₂ solutions of specific concentration, producing intergranular corrosion of the stainless steel in the sensitized condition.     

Synergistic inhibition between Schiff’s bases and sulfate ion on corrosion of aluminium in sulfuric acid

The effect of Schiff’s bases alone and Schiff’s bases with additive Na₂SO₄ on the corrosion of aluminium in H₂SO₄ have been investigated by using weight loss method. The present study revealed that aluminium in H₂SO₄ has been more efficiently inhibited by Schiff’s bases in the presence of additive Na₂SO₄ than Schiff’s bases alone due to the synergistic effect between Schiff’s bases and Na₂SO₄. Inhibition efficiency was found maximum upto 95.02% for aluminium in H₂SO₄ by Schiff’s bases in presence of additive NaNa₂SO₄. The adsorption of inhibitor accords with the Langmuir adsorption isotherm. Results obtained in both the cases indicate the dependence of inhibition efficiencies on the concentration of Schiff’s bases, additive Na₂SO₄ and also on the concentration of H₂SO₄ solution. The results show the increasing trends of inhibition efficiency with the concentration. The article is published in the original.     

The thermogalvanic corrosion of mild steel in alkaline solution—I. Actively dissolving electrodes

Using a simple model it has been shown that both thermodynamic and kinetic factors contribute to the temperature coefficient of the corrosion potential of a freely corroding electrode when the local action processes are under activation control. In the particular case of a 0·21%C steel immersed in deaerated Na₂B₄O₇/HCl buffer solution (pH 7·6) the kinetic factors predominate resulting in a negative coefficient. A thermogalvanic cell with a hot anode is therefore formed when when two such electrodes, maintained at different temperatures, are connected. In the absence of a significant cell internal resistance, a current will flow which reflects a stimulation of corrosion at the anode and a corresponding protection of the cathode, both attributable to thermogalvanic action. When the thermal e.m.f. is small the cell current overestimates the increased corrosion damage; since the individual electrodes are barely polarized it follows that the kinetics of the local action cathodic process at the anode cannot be ignored.     

Electrodeposition of multi-layer Pd–Ni coatings on 316L stainless steel and their corrosion resistance in hot sulfuric acid solution

Pd–Ni coating shows good corrosion resistance in strong corrosion environments. However, in complex aggressive environments, the performance of the coatings is limited and further improvement is necessary. The effects of the applied plating current density on the composition, structure and properties of Pd–Ni coatings were studied. By changing the current density in the same bath, multi-layer Pd–Ni coatings were prepared on 316L stainless steel. Scanning electronic microscopy, weight loss tests, adhesion strength, porosity and electrochemical methods were used to study the corrosion resistance of the films prepared by different coating methods. Compared with the single layer Pd–Ni coating, the multi-layer coatings showed higher microhardness, lower internal stress, lower porosity and higher adhesive strength. The multi-layer Pd–Ni coating showed obviously better corrosion resistance in hot sulfuric acid solution containing Cl^?.     

Dithizone and thiosemicarbazide as inhibitors of corrosion of type 304 stainless steel in 1·0M sulphuric acid solution

Abstract

Dithizone and thiosemicarbazide were investigated as inhibitors of the corrosion of type 304 stainless steel in 1·0M sulphuric acid solution by studying weight loss, polarisation curves, and polarisation resistance and using scanning electron microscopy and Auger electron spectroscopy. Various corrosion parameters such as Tafel slopes, corrosion rate, heat of adsorption, and activation energy were evaluated to understand the inhibition mechanism. Inhibition efficiency increased with an increase in concentration of both inhibitors and decreased with an increase in temperature. Both inhibitors seemed to obey the Langmuir adsorption isotherm equation. Dithizone was chemisorbed, whereas thiosemicarbazide was physisorbed on the surface of type 304 stainless steel. Dithizone acted as a mixed inhibitor, while thiosemicarbazide was cathodic in nature.     

The thermogalvanic corrosion of mild steel in alkaline solution—III. The factors controlling etching,passivation and pitting

The thermogalvanic behaviour of mild steel in an environment where active dissolution, passivation and breakdown are all possible has been investigated. The polarity of the electrodes and the magnitude of the cell currents vary with time as these processes occur successively but at different rates at each electrode. In the presence of an aggressive ion the onset of passivity is often undesirable since localized breakdown may ensue, any subsequent thermogalvanic corrosion being predominantly located at the pit sites giving rise to a disproportionate increase in metal penetration relative to the recorded current. Since maximum cell currents of approaching 5 A/m² are possible in these systems, the cells are usually under resistance control; any circumstance which leads to a lowering of this resistance will therefore increase the metal loss. However, thermogalvanic action does not always stimulate the overall corrosion rate of the anode but may, by polarization of this electrode, induce passivity and breakdown at a metal surface which would not undergo these changes spontaneously. Although the metal loss is often lowered, the penetration commonly increases since the corrosion damage which was previously uniform becomes highly localized.     

The thermogalvanic corrosion of mild steel in alkaline solution—II. Passivated electrodes under conditions of film breakdown

The thermogalvanic corrosion of mild steel in oxygen-saturated alkaline solution (ca. pH 9) with and without the addition of small amounts of Cl^? has been investigated. It is shown that the polarity of the electrodes is time-variable and that spontaneous passivation and subsequent breakdown of the protective film at these electrodes controls the magnitude of both the e.m.f. and the cell current. In the absence of the aggressive ion, the more rapid and complete passivation of the hot electrode leads to the eventual formation of a thermocell with a cold anode. The cell currents in this final stage are small (ca. 0·0016 A/m²) and reflect changes in the polarization of the local action processes rather than any increase in the metal loss attributable to thermogalvanic corrosion. By contrast, in the presence of Cl^?, the hot electrode ultimately becomes the anode of the cell as a result of both the more rapid and the more extensive breakdown of the passive film at higher temperatures. Significant thermogalvanic e.m.f.s (< 100 mV) and cell currents (< 0·16 A/m²) are recorded, the latter realistically representing the increased metal loss due to thermogalvanic action.     

Role of complexes in inhibition of mild steel by zinc–1-hydroxyethylidene-1, 1-diphosphonic acid mixtures

Abstract

The action of 1-hydrox yethylidene-1, 1-diphosphonic acid (HEDP) in combination with zinc ions as a corrosion inhibitor for mild steel in oxygen containing aqueous solutions has been investigated in relation to the presence of different zinc levels, the presence of aggressive anions, and different pH values. The highest inhibition effect was obtained at a 2·7:1 zinc/HEDP molar ratio, corresponding to 60 ppm zinc, and was associated with a significant anodic effect. In the absence of chloride and with no free forms of the inhibitor components, the zinc-HEDP mixture exhibited good protection over a wide range of pH (6·5-9·5). However, in a weakly acidic medium, protection could not be achieved. Calculations based on the dissociation constants of the HEDP and the stability constants of the possible zinc-HEDP complexes showed that this inhibition can be attributed to the presence of the 2:1 zinc-HEDP complex (Zn₂H_-1L^-) at a sufficient level. It is found that this anionic complex can behave as an anodic, passivating, inhibitor at a concentration as low as 0·00015M (20 ppm zinc-32 ppm HEDP mix ture). This passivity is prevented by the presence of sufficient chloride. The critical chloride concentration in these studies is approximately ten times higher than the complex concentration, in molar terms. It is also found that free phosphonate is aggressive and can prevent passivity due to the preferential formation of soluble iron-HEDP complex. The tolerance of the 2:1 complex to free phosphonate is substantially less than to chloride, approx imately equimolar.     

Investigation of steel corrosion in MX80 bentonite at 120°C

Corrosion experiments were performed on two metallic substrates, a ferritic–pearlitic steel (P285NH) and a ferritic one (Armco), in silicate environment during 30 days at 120°C. Corrosion products were characterized in terms of morphology (scanning electron microscope and transmission electron microscopy), composition (energydispersive X-ray spectroscopy) and structure (µ-Raman, selected area electron diffraction, X-ray absorption near edge structure). Results show a nanometric inner layer made of compact and adherent nanocrystallized magnetite with, locally a thickness up to several micrometers due to the metal microstructure. An outer layer of Fe-rich phyllosilicate, smectite and serpentine, more porous than the inner one and poorly adherent is observed around both the samples.     

Synergistic inhibition effect of N-(furan-2-ylmethyl)-7H-purin-6-amine and iodide ion for mild steel corrosion in 1 mol/L HCl

The synergistic inhibition effect of N-(furan-2-ylmethyl)-7H-purin-6-amine (FYPA) and iodide ion on mild steel corrosion in 1 mol/L HCl was investigated using weight-loss tests, electrochemical techniques, and surface analysis. The experiments revealed that the FYPA + KI mixture was a temperature-dependent inhibitor, which strongly inhibited the corrosion of mild steel compared with FYPA. Based on electrochemical results, FYPA and FYPA + KI behaved as mixed-type inhibitors, and their inhibition efficiencies were 73.66% and 96.01%, respectively. The calculated synergistic parameter value was larger than unity, illustrating that enhancement of inhibition in the presence of KI could be a result of synergistic action. Surface analysis techniques (scanning electron microscope/scanning electrochemical microscope) confirmed the presence of additives on the studied mild steel surface. A plausible mechanism of corrosion inhibition was proposed.     

The effect of thermodynamic parameters of the adsorption surfactants by lead on the lead’s corrosion rate

For several surfactants, free energies of adsorption (G_a⁰) are calculated relative to a symmetrically chosen standard state. It is shown that they characterize the strength of organic molecule-metal bond. The effect of these surfactants on active corrosion of lead in acetic acid solution, as well as correlation between the inhibition coefficient and the free energy of adsorption (G_a⁰), is studied by measuring the polarization resistance. The corrosion rate of lead in acetic acid solution with and without adding surfactants was studied gravimetrically. In this case, the corrosion rate was virtually independent of surfactant additives and their chemical nature; this is associated with the oxidation of lead surface.Translated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 56–60.Original Russian Text Copyright © 2005 by Afanasev, Akulova, Yakovleva.     

Evaluation of corrosion inhibition performance of silica sol–gel layers deposited on galvanised steel

The present work reports a comparative investigation of the electrochemical behaviour of some new types of silica sol–gel coatings with enhanced corrosion resistance deposited on electrolytically or thermally (hot-dip) zinc-coated steel. The coatings were rendered hydrophobic by silylation. Dichlorodimethylsilane or trimethylchlorosilane were used as silylating agents and cetyltrimethylammonium bromide or Pluronic PE 10300, as templating agents. The morpho-structural and optical properties of compact and mesoporous silica coatings were characterised with different methods. The corrosion behaviour of the coatings was evaluated by open circuit potential measurements, Tafel interpretation of the polarisation curves and electrochemical impedance spectroscopy. Both silylating agents improve significantly the corrosion resistance of both porous and compact coatings by reducing the corrosion current density with at least one order of magnitude. The possibility to use the porous structure of the coatings as corrosion inhibitor carriers was explored by loading of mesoporous silica layers with 1H-benzotriazole.     

Atmospheric corrosion kinetics and dynamics of electrogalvanized mild steel in southeastern coastal area of China–Pakistan Economic Corridor

This study aims to examine atmospheric corrosivity, corrodants, and corrosion products of southeastern coastal area of China–Pakistan Economic Corridor as per ISO protocols 9223 and 9225, and ASTM standards G1, G50, G140-02, D4458-94, and D2010. Test sites are located at National Institute of Oceanography (NIO) and Karachi Port Trust (KPT) at the banks of the Arabian Sea. Electrogalvanized mild steel test coupons were exposed, and levels of corrodants (sulfur dioxide, chloride, and time of wetness) were measured for a period of 24 months, from May 2014 to May 2016. Corrosivity category C5+ is established in terms of the corrosion rate for both NIO and KPT test stations, which does not coincide with the corrosivity category C5 ascertained by employing environmental characteristics and atmospheric corrodants. Corrosion kinetic parameter “n” and correlation coefficient (R²) are 0.71 and 0.97 for NIO and 0.96 and 0.97 for KPT, respectively. Scanning electron microscopy/energy-dispersive spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction spectroscopy have corroborated the presence of simonkolleite and hydrozincite, zinc oxide, zinc hydroxychloride, and zinc in corrosion products at both test sites.     

The effect of Sn on autoclave corrosion performance and corrosion mechanisms in Zr–Sn–Nb alloys

The desire to improve the corrosion resistance of Zr cladding material for high burn-up has resulted in a general trend among fuel manufacturers to develop alloys with reduced levels of Sn. While commonly accepted, the reason for the improved corrosion performance observed for low-tin zirconium alloys in high-temperature aqueous environments remains unclear. High-energy synchrotron X-ray diffraction was used to characterize the oxides formed by autoclave exposure on Zr–Sn–Nb alloys with tin concentration ranging from 0.01 to 0.92 wt.%. The alloys studied included the commercial alloy ZIRLO® (ZIRLO® is a registered trademark of Westinghouse Electric Company LLC in the USA and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited.) and two variants of ZIRLO with significantly lower tin levels, referred to here as A-0.6Sn and A-0.0Sn. The nature of the oxide grown on tube samples from each alloy was investigated via cross-sectional scanning electron microscopy. Atom probe analysis of ZIRLO demonstrated that the tin present in the alloy passes into the oxide as it forms, with no significant difference in the Sn/Zr ratio between the two. Synchrotron X-ray diffraction measurements on the oxides formed on each alloy revealed that the monoclinic and tetragonal oxide phases display highly compressive in-plane residual stresses with the magnitudes dependent on the phase and alloy. The amount of tetragonal phase present and, more importantly, the level of tetragonal-to-monoclinic phase transformation both decrease with decreasing tin levels, suggesting that tin is a tetragonal oxide phase stabilizing element. It is proposed that in Zr–Nb–Sn alloys with low Sn, the tetragonal phase is mainly stabilized by very small grain size and therefore remains stable throughout the corrosion process. In contrast, alloys with higher tin levels can in addition grow larger, stress stabilized, tetragonal grains that become unstable as the corrosion front continues to grow further inwards and stresses in the existing oxide relax.