Chloride Ion Environment Research Articles

Improving Producing Characteristics of Constructions through FE-NI and FE-NI-CR Alloy Coatings with a Given Structure

The article considers innovative materials that are recommended to be used as a coating for reinforcement of bearing structures of high-rise buildings, bridges, tunnels and underground structures, and as a coating for storagetanks of crude oil instead of high-alloy steel grades 20H23N18, 08H18N10. Nanostructural alloy coating Fe-Ni (> 80% Fe) and alloy coating Fe-Ni-Cr (> 70% Fe), containing in addition to α-Fe a new phase ε-Fe with hexagonal close-packed lattice (GPUr) were obtained by high frequency periodic current at atmospheric pressure and room temperature. Existence of phase ε-Fe was confirmed by X-ray diffraction method, electron-probe test with an electronic probe, scanning atomic force microscopy. Phase transition α-Fe → ε-Fe was observed in the deposition process. A special feature of this phase is the presence of a nanocrystal structure. The main factors in the formation of the hexagonal system are the frequency and duty cycle. The maximum number of ε-Fe phase in the Fe-Ni alloy is 30% and the alloy Fe-Ni-Cr is 20%. This phase has an essential effect on the producing characteristics of the studied coatings. Due to the corrosion resistance in the chloride ions environment Fe-Ni alloy deposited by a high frequency alternating current is 7.5 times greater than high-alloy steel 20X23H18 and 08H18N10. Additionally the nanostructure plated with Fe-Ni-Cr alloy coating made possible to increase its microhardness. Fe-Ni alloy coating can be used as coatings for storage tanks of crude oil and Fe-Ni-Cr alloy coating can be recommended to harden the supporting structures of high-rise buildings, bridges, tunnels and underground structures.

Corrosion protective properties of poly (4-(2-Thienyl) benzenamine) coating doped by dodecyl benzene sulphonate

Poly (4-(2-Thienyl) benzenamine) (PTBA) and corresponding homopolymers doped with sodium dodecyl benzene sulfonate (SDBS) and dedoped polymer coatings on steel surface have been synthesized by galvanostatic method. The anticorrosion performances of PTBA and its homopolymers coatings were investigated in 3.5wt% NaCl solution by the potentiodynamic polarization technique, Tafel test and electrochemical impedance spectroscopy (EIS). The PTBA was found to exhibit enhanced corrosion protection effect on stainless steel electrode in comparison with poly aniline (PANI) and poly thiophene (PTh) homopolymers. The corrosion rate of SDBS doped PTBA-coated steel was found ∼193 times lower than that of bare steel. Corrosion potential for uncoated steel increases (−0.506mV versus Ag/AgCl/Cl−(sat.)) to +40mV for SDBS doped PTBA-coated steel electrodes. The results of this study clearly indicate that the PTBA doped by SDBS has an outstanding potential to protect the steel against corrosion in a chloride ion environment.

A model of concrete carbonation depth under the coupling effects of load and environment

Based on the durability test data of the existing bridges in Hainan province, this study explored how the following factors, namely, the strength grade of concrete, stress condition, chloride ion content and environment influenced the depth of the concrete carbonation. A prediction model for the concrete carbonation depth of the in-service bridges in Hainan was established. The actual bridge carbonation data collected in recent years were employed to calculate the concrete quality impact coefficients. The impact on the carbonation depth of concrete from stress condition is large, the results show that the greater the concrete compressive stress, the slower the concrete carbonation rate; the larger the tensile stress, the faster the concrete carbonation rate. After inspection, it was found that the calculation results of the model agreed well with the bridge field test results, which suggested that the model would have good applicability.

Mesoporous silica based reservoir for the active protection of mild steel in an aggressive chloride ion environment

Spherical mesoporous silica (m-SiO2) with well-ordered pores was synthesized by a modified Stöber method using CTAB micelles.

Cu-based Fe phosphate coating and its application in CO2 pipelines

Transportation of CO2 via steel pipelines from CO2 sources to storage wells will be required in the capture and storage (CCS) cycle. However if the CO2 stream contains contaminants, internal localized CO2 corrosion could occur. Further corrosion protection is also required to transport fluids in the hydrocarbon and chemical process industries if such fluids are acidified by in-situ speciation of carbonic acid (and other impurities). In this context, we report the feasibility of nanostructured Cu-based Fe phosphate coatings as a protection system for the interior surface of steel pipelines in acidified environments. Cu-based Fe phosphate coatings were deposited on mild steel surface via chemical conversion and electroless process. The idea behind phosphate protection is to build a thin dense phosphate layer (1.8μm) that composed of Cu-nanoparticles (5–20nm) attached to Fe phosphate plates of length 0.5–3μm. The presence of nanostructured CuFe phosphate crystals and the suppression of the coating's pore formation are beneficial for enhancement the corrosion resistance of steel in chloride ions environment at pH1 and 2. The passivation performance of CuFe phosphate coatings were examined by electrochemical studies namely: potentiodynamic polarization and electrochemical impedance spectroscopy.

Research on the Failure Mechanism of Pitting Corrosion of the 304 Stainless Steel in Chloride Ions Environment

The Mechanism of 304 Stainless Steel Pitting Corrosion Was Researched in Chloride Ions Environment. the Metallographic Microstructure of Areas near the Pitting Corrosion and Far Away from the Pitting Corrosion Were Observed by the Metallographic Experiment；Cr Content of the Sample Was Determined by EDXRF, to Prove Chloride Ion Impact on the Element Cr of 304 Stainless Steel. Finally, Corrosion Rate of Specimens Was Determined by Piecewise Experiment Method to Prove Otherness for Corrosion Rate in Different Period of 304 Stainless Steel in Chloride Ions Environment.

Research of G105 Chloride Ion Stress Corrosion Cracking

At present, there are also very few regarding drill pipe's SCC research in chloride ion ambient medium, so it is specially important to definite the stress corrosion sensitivity of drill pipe to the influence under different chloride ion density and to provide the appraisal basis for the influence of the chloride ion density to drill pipe's corrosion. Applied the G105 drill pipe material to do Slow Stress Rate Testing (SSRT) and the electrochemical experiment under the different chloride ion environment, analyzed the variation of corrosion current and corrosion potential and observed the fracture. The results show that all of the tensile specimens' fracture morphologies are brittle fracture; and the stress corrosion cracking sensitivity of the material increases gradually with the addition of chloride ion concentration; the corrosion rate also tends to increase, but when the chloride concentration is 6000, the corrosion rate is up to a extreme value; the effect of chloride concentration to the cathode is much more than that to the anode, but the G105 pipe corrosion in different chloride solution is controlled differently. The stress can improve the stress corrosion cracking sensitivity of material in corrosion solution. The anti-corrosion principle of chloride ion corrosion is: to reduce adsorption of chlorine ion on the surface.

The effect of β-FeOOH on the corrosion behavior of low carbon steel exposed in tropic marine environment

The atmospheric corrosion performance of carbon steel exposed in Wanning area, which located in the south part of China with tropic marine environment characters, was studied at different exposure periods (up to 2 years). To investigate the effect of β-FeOOH on the corrosion behavior of carbon steel in high chloride ion environment, rust layer was analyzed by using infrared spectroscopy, scanning electron microscope, X-ray diffraction, and the rusted steel was measured by electrochemical impedance spectroscopy method. The weight loss test indicated that the corrosion rate of carbon steel sharply increased during 6 months’ exposure and gradually reduced after longer exposure. The results of rust analysis revealed that the underlying corrosion performance of the carbon steel was dependent on the inherent properties of the rust layers formed under different conditions such as composition and structure. Among all the iron oxide, β-FeOOH exerted significant influence. The presence of a monolayer of the rust as well as β-FeOOH accelerated the corrosion process during the initial exposure stage. EIS data implied that β-FeOOH in the inner layer was gradually consumed and transformed to γ-Fe2O3 in the wet-dry cycle, which was beneficial to protect the substrate and reduced the corrosion rate.

A high-field solid-state 35/37Cl NMR and quantum chemical investigation of the chlorine quadrupolar and chemical shift tensors in amino acid hydrochlorides

A series of six L-amino acid hydrochloride salts has been studied by 35/37Cl solid-state NMR spectroscopy (at 11.75 and 21.1 T) and complementary quantum chemical calculations. Analyses of NMR spectra acquired under static and magic-angle-spinning conditions for the six hydrochloride salts, those of aspartic acid, alanine, cysteine, histidine, methionine and threonine, allowed the extraction of information regarding the chlorine electric field gradient (EFG) and chemical shift tensors, including their relative orientation. Both tensors are found to be highly dependent on the local environment, with chlorine-35 quadrupolar coupling constants (CQ) ranging from -7.1 to 4.41 MHz and chemical shift tensor spans ranging from 60 to 100 ppm; the value of CQ for aspartic acid hydrochloride is the largest in magnitude observed to date for an organic hydrochloride salt. Quantum chemical calculations performed on cluster models of the chloride ion environment demonstrated agreement between experiment and theory, reproducing CQ to within 18%. In addition, the accuracy of the calculated values of the NMR parameters as a function of the quality of the input structure was explored. Selected X-ray structures were determined (L-Asp HCl; L-Thr HCl) or re-determined (L-Cys HCl.H2O) to demonstrate the benefits of having accurate crystal structures for calculations. The self-consistent charge field perturbation model was also employed and was found to improve the accuracy of calculated quadrupolar coupling constants, demonstrating the impact of the neighbouring ions on the EFG tensor of the central chloride ion. Taken together, the present work contributes to an improved understanding of the factors influencing 35/37Cl NMR interaction tensors in organic hydrochlorides.

Solid-State35/37Cl NMR Spectroscopy of Hydrochloride Salts of Amino Acids Implicated in Chloride Ion Transport Channel Selectivity: Opportunities at 900 MHz

The results of a detailed systematic chlorine solid-state NMR study of several hydrochloride salts of amino acids implicated in chloride ion transport channel selectivity are reported. (35)Cl and (37)Cl NMR spectra have been obtained for stationary and/or magic-angle spinning powdered samples of the following compounds on 500 and/or 900 MHz spectrometers: DL-arginine HCl monohydrate, L-lysine HCl, L-serine HCl, L-glutamic acid HCl, L-proline HCl, L-isoleucine HCl, L-valine HCl, L-phenylalanine HCl, and glycine HCl. Spectral analyses provide information on the anisotropic properties and relative orientations of the chlorine electric field gradient and chemical shift (CS) tensors, which are intimately related to the local molecular and electronic structure. Data obtained at 900 MHz provide unique examples of the effects of CS anisotropy on the NMR spectrum of a quadrupolar nucleus. The range of chlorine quadrupolar coupling constants (C(Q)) measured, -6.42 to 2.03 MHz, demonstrates the sensitivity of this parameter to the chloride ion environment and suggests the applicability of chlorine solid-state NMR as a novel experimental tool for defining chloride binding environments in larger ion channel systems. Salts of hydrophobic amino acids are observed to tend to exhibit larger values of C(Q) than salts of hydrophilic amino acids. A simple model for rationalizing the observed trend in C(Q) is proposed. For salts for which neutron diffraction structures are available, we identify a quantum chemical method which reproduces experimental values of C(Q) with a root-mean-square deviation of 0.1 MHz and a correlation coefficient of 0.9998. On the basis of this, chlorine NMR tensors are predicted for the Cl(-) binding site in ClC channels.