Synergistic effect of polyaspartic acid and iodide ion on corrosion inhibition of mild steel in H2SO4

The inhibition effect of polyaspartic acid (PASP) and its synergistic effect with KI on mild steel corrosion in 0.5 M H₂SO₄ solution are studied by weight loss and electrochemical methods. The inhibition efficiency increases with the concentration of PASP and increases further with the presence of 1 mM KI. Result of the zero charge potential measurement shows that iodide ion promotes the film formation of PASP greatly. The mild steel surfaces after immersion test were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. An adsorption model is proposed to elucidate the synergistic mechanism of synergistic effect.     

Hydroxymethyl urea and 1,3-bis(hydroxymethyl) urea as corrosion inhibitors for steel in HCl solution

The inhibition effect of two urea derivatives of hydroxymethyl urea (HMU) and 1,3-bis(hydroxymethyl) urea (BHMU) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), quantum chemical calculation and molecular dynamics (MD) simulation methods. Inhibition efficiency values of 20.0 mM HMU and BHMU are higher than 80% and 85% at 20–50 °C, respectively. The adsorption of each inhibitor on steel surface obeys Langmuir adsorption isotherm, and is mainly the chemical adsorption. Inhibition efficiency follows the order: BHMU > HMU.     

Effects of pH value on characteristics of oxide films on 316L stainless steel in Zn-injected borated and lithiated high temperature water

The effects of pH values from 6.9 to 7.4 on oxide films for 316L stainless steel in borated and lithiated high temperature water at 573.15 K without and with Zn injection were examined by in situ potentiodynamic polarization curves, electrochemical impedance spectra and ex situ X-ray photoelectron spectroscopy (XPS) analysis. The composition of oxide films appears slightly pH dependent: rich in chromites and ferrites at pH = 6.9 and pH = 7.4, respectively. The corrosion rate decreases significantly in the high pH value solution with Zn injection due to the formation of compact oxide films. The solubilities and structural model of oxides are proposed and discussed.     

Atmospheric corrosion of Ni-advanced weathering steels in marine atmospheres of moderate salinity

One conventional and three Ni-advanced weathering steels have been exposed for one year in two marine atmospheres of moderate aggressivity (30 and 75 mg Cl⁻/m² d). The rusts generated have been analysed by polarised light optical microscopy, SEM, XRD, Raman spectroscopy and Mössbauer spectroscopy.The presence of high nickel (1–3% weight) contents in the steel composition leads to higher corrosion resistance in moderate marine atmospheres. The presence of nickel in the weathering steel also raises the proportion of nanophasic (superparamagnetic) goethite in the inner rust layer.     

Resistance to oxidation and ablation of SiC coating on graphite prepared by chemical vapor reaction

A thick SiC coating was prepared on graphite by chemical vapor reaction. The coating reveals a typical crystalline structure with limited porosity and combines well with the substrate. Oxidation tests demonstrate that the coating has a weak self-healing ability at 1100 K and good self-healing ability at temperatures from 1623 to 1823 K. An oxyacetylene torch test verifies that the prepared coating can effectively protect graphite from ablation for 50 s. After the ablation test, the silica microspheres and other interesting silica structures such as microwires, microparticles, microflowers, nanowires and nanoparticles are formed at the ablation center and its surroundings.     

The high-temperature oxidation of bulk nanocrystalline 304 stainless steel in air

The high-temperature oxidation of bulk nanocrystalline 304 stainless steel (BN-SS304) and its conventional polycrystalline counterpart (CP-SS304) in air at 900 °C for 24 h were studied by thermogravimetric analysis, X-ray photoelectron spectroscopy and scanning electron microscope. We studied the valence electron configurations of BN-SS304, CP-SS304 and their oxide scales by ultra-violet photoelectron spectroscopy. The high-temperature oxidation resistance of BN-SS304 was enhanced in both initial and isothermal oxidation, which was attributed to its larger work function and more chemical stability, its more chemically stable and compact oxide scale, its weaker O₂ adsorption and diffusion, its weaker Cr and Mn atoms diffusions.     

EIS assessment of critical pitting temperature of 2205 duplex stainless steel in acidified ferric chloride solution

In this study, critical pitting temperature (CPT) of 2205 duplex stainless steel (DSS2205) was assessed using electrochemical impedance spectroscopy (EIS) in ferric chloride solution. In order to verify the results other methods such as ASTM G 48, potentiodynamic and potentiostatic polarisation and zero resistance ammeter (ZRA) were also employed. The results show a strong close relation between the results of this method by those of previous methods. CPT of the alloy is 40 °C based on standard method and 44 °C, 49 °C according to the ZRA and potentiostatic methods. Both potentiodynamic and EIS methods give an almost identical CPT value.     

Novel benzimidazole derivatives as corrosion inhibitors of mild steel in the acidic media. Part I: Gravimetric,electrochemical, SEM and XPS studies

Three novel benzimidazole derivatives, 2-aminomethyl benzimidazole (ABI), bis (2-benzimidazolylmethyl) amine (BBIA) and tri (2-benzimidazolylmethyl) amine (TBIA), have been studied as inhibitors for mild steel in 1.0 M HCl. The three compounds prevent mild steel from corrosion by adsorption on the steel surface and forming insoluble complex with ferrous species. Inhibition efficiency increases with the increase in the number of benzimidazole segments in the molecules (TBIA > BBIA > ABI). Protection efficiency of the inhibitors depends on concentration of inhibitor, temperature and concentration of hydrochloric acid.     

Glass coatings on stainless steels for high-temperature oxidation protection: Mechanisms

The oxidation behavior of a martensitic stainless steel with or without glass coating was investigated at 600–800 °C. The glass coating provided effective protection for the stainless steel against high-temperature oxidation. However, it follows different protection mechanisms depending on oxidation temperature. At 800 °C, glass coating acts as a barrier for oxygen diffusion, and oxidation of the glass coated steel follows linear law. At 700 or 600 °C, glass coating induces the formation of a (Cr, Fe)₂O₃/glass composite interlayer, through which the diffusion of Cr³⁺ or Fe³⁺ is dramatically limited. Oxidation follows parabolic law.     

Adsorption and inhibition effect of Ascorbyl palmitate on corrosion of carbon steel in ethanol blended gasoline containing water as a contaminant

The adsorption and inhibition effect of Ascorbyl palmitate (AP) on carbon steel in ethanol blended gasoline containing water as a contaminant (GE10 + 1%water) was studied by weight loss and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the addition of ethanol and water to gasoline increase the corrosion rate of carbon steel. AP inhibits the corrosion of carbon steel in (GE10 + 1% water) solution to a remarkable extent. The adsorption of AP on the carbon steel surface was found to obey the Langmuir adsorption isotherm model. The values of activation energy (E_a) and various thermodynamic parameters were calculated and discussed.     

Long-term monitoring of atmospheric corrosion at weathering steel bridges by an electrochemical impedance method

Weathering steel corrosion was monitored for one to two years under natural atmosphere by an electrochemical impedance technique. Two identical comb-shape weathering steel sheets embedded in epoxy resin were used as monitoring probe electrodes at two different bridges in Japan. Impedances at 10 kHz (Z_10kHz) and 10 mHz (Z_10mHz) were automatically measured every hour. Coupons (50 × 50 × 2 mm³) prepared from the same steel sheets were exposed together to measure the corrosion mass loss. The average (Z_10mHz)⁻¹ value for half to one year exposure correlated well with the average corrosion rate determined from the corrosion mass loss.     

Characterization of corrosion products formed on Ni 2.4 wt%–Cu 0.5 wt%–Cr 0.5 wt% weathering steel exposed in marine atmospheres

Weathering steel manufactured with high concentrations of copper (0.5 wt%), chromium (0.5 wt%) and nickel (2.4 wt%) was studied with the aim of furthering knowledge on corrosion product characterization and performance in marine environments. Specimens exposed for two years in a rural atmosphere and two marine environments were characterized by optical microscopy, SEM/EDS, XRD and Raman spectroscopy and corrosion rates measured. The main phases found were ferrihydrite, maghemite and goethite in the inner corrosion layer, and lepidocrocite in the outer layer. Cu and Ni were homogeneously distributed while Cr tended to be concentrated in the inner layer.     

Investigation of corrosion inhibition mechanism and stability of Vitamin B1 on mild steel in 0.5 M HCl solution

The corrosion inhibition mechanism and the stability of Vitamin B1 (VitB1) on mild steel in 0.5 M HCl solution were investigated. Surface of the steel after exposing to test solutions were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX). The stability of the inhibitor film was investigated by electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and cyclic voltammetry (CV) techniques. It was found that VitB1 acts by adsorption on mild steel via physical and chemical interactions and a protective film formation. The inhibitor film evenly distributes over the steel surface and is stable.     

Application of automated electrical resistance sensors for measurement of corrosion rate of copper,bronze and iron in model indoor atmospheres containing short-chain volatile carboxylic acids

The corrosion rate of copper and bronze Cu-8 wt.%Sn increased rapidly when the concentration of formic or acetic acid in air reached about 300 ppb at 80% relative humidity (RH) and a temperature of 20 °C. It decreased slowly during the several days after pollutant removal due to the slow rate of pollutant desorption from the metal surfaces. Corrosion of these metals was barely affected by the acids at RH up to 60%. For iron, the critical concentration of formic acid in air which led to surface activation at 80% RH was between 1000 and 1590 ppb.     

Sulphuric acid corrosion of ultrafine-grained mild steel processed by equal-channel angular pressing

A bulk ultrafine-grained (UFG) mild steel with a ferrite grain size of approximately 200 nm and a dispersed distribution of iron carbide particles was fabricated by equal-channel angular pressing (ECAP) at 400 °C. The corrosion behaviour of the ECAP-processed mild steel and pure iron was investigated in a 0.5 mol/L H₂SO₄ solution. They exhibited a higher corrosion rate and better anodic passivity properties due to the presence of more crystalline defects. As a result of the refinement of the iron carbide particles, the forming ability of a continuous dense passive film was improved.     

Electrochemical and quantum chemical studies of some azomethine compounds as corrosion inhibitors for mild steel in 1 M hydrochloric acid

The corrosion inhibition effect of new azomethine compounds: PhNNC (COCH₃)NC₆H₄Y {Y = OCH₃ (SB₁), CH₃ (SB₂), H (SB₃), Br (SB₄) and Y = Cl (SB₅)} on mild steel in 1 M HCl, was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemistry analysis. It has been found that the inhibition efficiency increased with increasing inhibitor concentration. The polarization curves showed that these Schiff bases function as mixed inhibitors. The adsorption of studied compounds on mild steel surface was found to follow the Langmuir isotherm. Molecular modeling was used to correlate corrosion inhibition properties and calculated quantum chemical parameters.     

Development of carbon nanotubes reinforced hydroxyapatite composite coatings on titanium by electrodeposition method

Carbon nanotubes (CNTs) are outstanding reinforcement material for imparting strength and toughness to brittle hydroxyapatite (HAP). This work reports the electrodeposition of CNTs reinforced HAP on titanium substrate at −1.4 V vs. SCE during 30 min with the functionalised CNTs concentration ranging from 0 to 2 wt.%. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HRTEM), mechanical and biological studies were used to characterise the coatings. Also, the corrosion resistance of the coatings was evaluated by electrochemical techniques in simulated body fluid (SBF) solution.     

Early stage oxidation of Ni–Cr binary alloy (1 1 1), (1 1 0) and (1 0 0) surfaces: A combined density functional and quantum chemical molecular dynamics study

First-principles and tight-binding quantum chemical molecular dynamics were used in this study. The chemisorption energies of O and OH on the Ni–Cr (1 1 0) surface are lower than those of other surfaces. The oxygen 2p orbitals hybridise with Ni 3d, 4s and small amounts of p orbitals for the (1 0 0) surface while Ni p orbitals have no contribution for the (1 1 0) surface, which might reduce the adsorption energy. Additionally, oxygen acquires the maximum depth into the Ni–Cr (1 1 0) surface. Applied strain increases the oxygen diffusivity. This study reveals that the Ni–Cr (1 1 0) surface is easier for oxygen diffusion accordingly oxidation accelerates.     

Design and synthesis of a novel class of inhibitors for mild steel corrosion in acidic and carbon dioxide-saturated saline media

p-(9-(2-Methylisoxazolidin-5-yl)nonyloxy)benzaldehyde I, prepared using a cycloaddition protocol, was elaborated into its cinnamaldehyde derivative II which upon quarternization with propargyl chloride afforded III bearing an interesting blend of structural traits suitable for imparting inhibition of mild steel corrosion. Novel compounds I–III showed efficient inhibition against mild steel corrosion in CO₂–0.5 M NaCl (40 °C, 1 atm; 120 °C, 10 bar), 1, 4, 7.7 M HCl, and 0.5 M H₂SO₄ at 60 °C as determined by gravimetry and electrochemical methods. The presence of carbonaceous surface and nitrogen, as revealed by XPS study, indicated the formation of a film covering the metal surface, which imparted corrosion inhibition.     

Effect of surface preparation on the corrosion of austenitic stainless steel 304L in high temperature steam and simulated PWR primary water

The corrosion behavior of 304L grade stainless steel (SS) in high-temperature steam and in a simulated Pressurized Water Reactor (PWR) is studied. The goal was to characterize the nature of the oxide coating generated during 500 h exposure of samples in a 400 °C steam (200 bar) or a 340 °C simulated PWR. Accelerating the effect of the steam environment as well as the influence of surface preparation have been studied. Two initial sample surfaces were used: mechanical polishing and finishing grinding. Oxide coatings were investigated using TEM imaging coupled with EELS spectroscopy and R – SIMS (Secondary Ion Mass Spectroscopy).