Effect of nitrate and chromate on the localized corrosion of iron and nickel

1981 ◽  
Vol 46 (11) ◽  
pp. 2834-2841 ◽  
Author(s):  
Jaromír Toušek
Keyword(s):  
Activation Energy ◽  
Corrosion Rate ◽  
Competitive Adsorption ◽  
Localized Corrosion ◽  
Favourable Effect ◽  
Water Molecules ◽  
Metal Dissolution ◽  
Breakdown Potential ◽  
Passivation Potential ◽  
Corrosion Of Iron

The combined effect of some inorganic inhibitors - chromate and nitrate - on the rate of localized corrosion of iron and nickel was investigated. The efficiency of these inhibitors and the mechanism of their effect were found to depend on the potential. If the breakdown potential is lower than the second passivation potential, the corrosion rate decreases owing to the competitive adsorption of inhibitor and of aggresive ions and owing to a change in the activation energy of the metal dissolution. Substances that are strongly adsorbed on the electrode act in this region as strong inhibitors. In the range of the second passivation potential there operates another mechanism consisting in a favourable effect of the water molecules in the inhibitor hydration sphere on the rate of the passivation reaction. In this range, even such substances that are only weakly adsorbed on the electrode can act as strong inhibitors.

The Calculation of the Thickness for Uniform Corrosion and Localized Corrosion in Steel Corrosion

2011 ◽  
Vol 255-260 ◽  
pp. 514-518
Author(s):  
Zheng Yi Kong ◽  
Shan Hua Xu ◽  
Yu Sheng Chen
Keyword(s):  
Corrosion Rate ◽  
Constant Temperature ◽  
Safety Assessment ◽  
Steel Corrosion ◽  
Localized Corrosion ◽  
Power Relationship ◽  
Uniform Corrosion ◽  
Experiment Data ◽  
Temperature And Humidity ◽  
Corrosion Pits

Because of the complexity of corrosion, the law of uniform corrosion and localized corrosion is still not clear,so it is difficult to assess their impact on the structure safety. In order to differ them and find their own law, we obtain a lot of corrosion specimens by ways of constant temperature and humidity, and then detect the size of corrosion pits by roughness tester. After that, the method for calculating the thickness of uniform corrosion and localized corrosion is proposed. Then the method is used to analyze the experiment data. The result indicates the thickness of uniform corrosion and localized corrosion all increase with the rate of corrosion, and they all show a power relationship with corrosion rate, so it will provide a basis for distinguishing them in safety assessment.

scholarly journals Removal of Chromium from Aqueous Solution Using Modified Pomegranate Peel:Mechanistic and Thermodynamic Studies

2009 ◽  
Vol 6 (s1) ◽  
pp. S153-S158 ◽  
Author(s):  
Tariq S. Najim ◽  
Suhad A. Yassin
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Aqueous Solution ◽  
Adsorption Process ◽  
Batch Process ◽  
The Other ◽  
Water Molecules ◽  
Pomegranate Peel ◽  
Solution Interface ◽  
Adsorbent Surface

Modified pomegranate peel (MPGP) and formaldehyde modified pomegranate peel (FMPGP) were prepared and used as adsorbent for removal of Cr(VI) ions from aqueous solution using batch process. The temperature variation study of adsorption on both adsorbents revealed that the adsorption process is endothermic, from the positive values of ∆H˚. These values lie in the range of physisorption. The negative values of ∆G˚ show the adsorption is favorable and spontaneous. On the other hand, these negative values increases with increase in temperature on both adsorbents, which indicate that the adsorption is preferable at higher temperatures. ∆S˚ values showed that the process is accompanied by increase in disorder and randomness at the solid solution interface due to the reorientation of water molecules and Cr(VI) ions around the adsorbent surface. The endothermic nature of the adsorption was also confirmed from the positive values of activation energy, Ea, the low values of Ea confirm the physisorption mechanism of adsorption. The sticking probability, S*, of Cr(VI) ion on surface of both adsorbents showed that the adsorption is preferable due to low values of S*(0< S*< 1 ), but S*values are lower for FMPGP indicating that the adsorption on FMPGP is more preferable .

scholarly journals Corrosion Study of Iron and Copper Metals and Brass Alloy in Different Medium

2011 ◽  
Vol 8 (s1) ◽  
pp. S344-S348 ◽  
Author(s):  
Memon Samina ◽  
Abdul Karim ◽  
A. Venkatachalam
Keyword(s):  
Corrosion Rate ◽  
Brass Alloy ◽  
Corrosion Study ◽  
Iron Copper ◽  
Corrosion Of Iron

The corrosion of iron, copper and brass alloy has been investigated in different mediumi.e. HNO3, H3PO4, H2SO4, HCl, CH3COOH. The study reveals that corrosion rate increases in the order iron > copper > brass and for the medium the corrosion follows the order HNO3> H3PO4> H2SO4> HCl > CH3COOH. The rate of corrosion increases with increasing concentration of acid and with increase in time.

Strain Enhanced Corrosion in the Iron-Caustic System

CORROSION ◽  
1976 ◽  
Vol 32 (9) ◽  
pp. 353-357 ◽  
Author(s):  
RONALD B. DIEGLE ◽  
DAVID A. VERMILYEA
Keyword(s):  
Steady State ◽  
Corrosion Rate ◽  
Strain Rate ◽  
Electrolyte Concentration ◽  
Applied Strain ◽  
Crack Advance ◽  
Film Rupture ◽  
Applied Strain Rate ◽  
Corrosion Of Iron ◽  
Kinetics Of

Abstract Straining electrode experiments were performed to investigate the nature of strain enhanced corrosion of iron in caustic electrolyte. The strain enhanced corrosion rate was generally linearly dependent on applied strain rate, and its potential dependence paralleled that of steady-state polarization behavior on non-straining electrodes. Data was presented as ratios, in which is the corrosion rate in cm/s and is the corresponding strain rate. This ratio, which was shown in a previously published theory to be numerically equal to the crack advance per film rupture event during film rupture SCC, depended on electrochemical variables such as electrolyte concentration and temperature in a manner similar to the kinetics of caustic cracking. Conditions which are known to be marginal in producing caustic cracking resulted in values for of about 10−7 cm, in excellent agreement with a previously developed theory. It was concluded that strain enhanced corrosion in this system results from repetitive film rupture and repair during straining.

scholarly journals Application of Kelvin Probe Force Microscopy (KFM) to Evidence Localized Corrosion of Over-Aged Aeronautical 2024 Aluminum Alloy

2013 ◽  
Vol 550 ◽  
pp. 127-134
Author(s):  
Nicoleta Radutoiu ◽  
Joël Alexis ◽  
Loïc Lacroix ◽  
Marioara Abrudeanu ◽  
Jacques Alain Petit
Keyword(s):  
Aluminum Alloy ◽  
Corrosion Rate ◽  
Pitting Corrosion ◽  
Corrosion Damage ◽  
Localized Corrosion ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Intermetallic Particles ◽  
2024 Alloy ◽  
The Matrix

The 2xxx serie aluminum alloys are characterized by good mechanical performances and low density, however they are susceptible to different forms of localized corrosion: pitting corrosion, intergranular corrosion and stress corrosion cracking. The 2024-T351 aluminum alloy is used in the aircraft industry for numerous applications such as fuselage and door skin. Corrosion damage of the material is also very detrimental for the structural integrity of the aircraft. The presence of coarse intermetallic particles, with a heterogeneous size distribution was found to be responsible for the 2024 susceptibility to localized corrosion. These particles are generally the cause of initiation sites. Presence of micro-defects in the oxide film upon coarse intermetallic particles and the galvanic coupling with the matrix contribute to the development of pitting corrosion. The over-ageing treatment (T7) is supposed to stabilize the microstructure and the mechanical properties to improve the corrosion resistance. The 2024 alloy microstructure after the T7 heat treatment remains very complex. The 2024 alloy corrosion behavior was studied in the over-ageing state for three different temperatures (150, 175 and 190 °C). During the corrosion tests in chloride-containing environment, the behavior of coarse intermetallic particles was found to be different. Thus, the 2024 samples suffer a gradual attack upon S-Al2CuMg particles and finally Al (Cu,Mn,Fe,Si) particles. The corrosion damage was studied by Atomic Force Microscopy (AFM) and Kelvin probe Force Microscopy (KFM). This technique allows simultaneous topographical and electric potential mapping to be obtained. This latest potential was shown to be correlated to the corrosion potential of the 2024 alloy. This study focuses on the variation of the KFM potential of the coarse intermetallic particles and the matrix for the over-ageing conditions (T7). Observations using optical microscope and AFM were also performed to obtain the corrosion rate for each condition. The corrosion rate was correlated to the chemical composition variation of the particles obtained by scanning electron microscope observations and EDS analyses.

Superior water anchoring hydrogel validated by colorimetric sensing

2020 ◽  
Vol 7 (12) ◽  
pp. 3250-3257
Author(s):  
Xiaoyun Hu ◽  
Zhiwei Ma ◽  
Jiguang Li ◽  
Zhenzhen Cai ◽  
Yushu Li ◽  
...  
Keyword(s):  
Activation Energy ◽  
Water Molecules ◽  
Colorimetric Sensing

A superior water anchoring hydrogel with alternating hydrophilic and hydrophobic structures effectively reduces the kinetic activation energy of water molecules and significantly inhibits the color diffusion of dye particles and the reaction product.

scholarly journals Inhibition Effect of Tartrate Ions on the Localized Corrosion of Steel in Pore Solution at Different Chloride Concentrations

Buildings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 105
Author(s):  
Marina Cabrini ◽  
Sergio Lorenzi ◽  
Denny Coffetti ◽  
Luigi Coppola ◽  
Tommaso Pastore
Keyword(s):  
Competitive Adsorption ◽  
Pore Solution ◽  
Chloride Concentration ◽  
Chelating Agent ◽  
Localized Corrosion ◽  
Ferric Ions ◽  
Electrochemical Tests ◽  
Inhibition Effect ◽  
Passive Current ◽  
Corrosion Of Steel

The aim of this work is the evaluation of the inhibition effect of tartrate ions with respect to the localized corrosion of steel reinforcements in alkaline solution as a function of the concentration of chlorides ions. Weight loss tests and electrochemical tests were carried out in saturated Ca(OH)2 solution with NaOH at pH 12.7 and 13.2. The results only evidence a slight inhibition effect at pH 12.7, whereas at pH 13.2 the pitting onset is inhibited also for chloride concentration up to 3 M. Tartaric acid is a dicarboxylic acid with nucleophile substituents, which can act as a chelating agent both adsorbing on the surface of the passive film and forming a soluble complex with ferrous and ferric ions. Tartrate causes an increase in the passive current density but it prevents the depassivation of carbon steel due to the action of chlorides, thus preventing pitting initiation due to the competitive adsorption on metal surface.

2H and 195 Pt NMR Studies of Molecular and Electron Spin Dynamics in Paramagnetic [Cu(H2O)6][PtCl 6]

1998 ◽  
Vol 53 (6-7) ◽  
pp. 447-452
Author(s):  
Takahiro Iijima ◽  
Kengo Orii ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Activation Energy ◽  
Electron Spin ◽  
Nmr Spectra ◽  
Chemical Shift Anisotropy ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Temperature Phase ◽  
Nmr Studies ◽  
Teller Distortion ◽  
Exponential Factor

Abstract The temperature dependences of 2H and 195Pt NMR spectra and the spin-lattice relaxation time T1 were measured for [Cu(H2O)6][PtCl6]. From the simulation of 2H NMR spectra, the jump rate of 180° flips of the water molecules (k), the nuclear quadrupole interaction parameters (e2Qq/h, ƞ) and the electron-nucleon dipolar interaction parameter (vD) were obtained. By measuring 2H T1, k was estimated in the temperature range where the spectrum is insensitive to the motion of the water molecules. Above the phase transition temperature, the pre-exponential factor k0 = 8 x1011 s-1 and the activation energy Ea = 15 kJmol-1 for 180° flips of the water molecules were obtained from the spectral simulation and T1. 195Pt NMR spectra showed an axially symmetric and unsymmetric powder pattern of the chemical shift anisotropy at the high and low temperature phase, respectively. For the deuterated compound, the correlation times of the electron spin in Cu2+ were estimated from 195Pt T1 and the activation energy for jumping between the different configurations of Jahn-Teller distortion Δ = 200 K was obtained.

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