G. Carbajal-De la Torre

Corrosion protection of 1008 carbon steel by hybrid coatings

Abstract Potentiodynamic polarisation curves have been used to evaluate the corrosion performance of 1008 carbon steel coated with hybrid (inorganic-organic) and mixed oxide coating systems deposited by dip coating. Several coatings have been prepared by the sol-gel method, using metallic alkox ides, such as tetraethylorthosilicate, aluminium isopropoxide, and zirconium propoxide, and polymers like allyl methacrylate (AMA) and polymethylmethacrylate (PMMA), together with zirconium dioxide (ZrO2) and silicon and aluminium oxides (SiO3-Al2O3). The aqueous test solutions included hydrochloric acid (HCl), sodium chloride (NaCl), and sulphuric acid (H 2SO4) at various concentrations (0·1, 0·5, and 1M). Scanning electron microscopy was used to examine the coatings following testing. The results have shown that SiO2-Al2O3 based coatings are not beneficial for corrosion protection in HCl, but are of value in the other aqueous media. In 1·0M HCl, the best protection was offered by a hybrid SiO2-ZrO2-poly(methylmethacrylate-allyl methacrylate) (P(MMA-AMA)) coating. In NaCl, the best results, were generally obtained with SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. Similarly, in H2SO4, the best results were generally displayed by the SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. The corrosion behaviour of the coatings is discussed in terms of the integrity and stability of the film.

Surface Tension and Interfacial Tension Measurements in Water-Surfactant-Oil Systems Using Pendant Drop Technique

The study and modeling of physical properties such as surface tension and interfacial tension are important factors in the formation and stability of fluid systems such as emulsions. The present work shows the experimental results for surface tension and interfacial tension measurements in water and/or oils systems in the presence of surfactants, using the pendant drop technique. Distilled water and straight-chain alkanes such as hexane, dodecane and hexadecane were used. The surfactants employed were sodium dodecyl sulphate (SDS) and sorbitan monooleate (SPAN 80), which are hydrophilic and lipophilic surfactants respectively. Some results show the dependence of surface tension or interfacial tension with respect to the surfactant concentration, other results were obtained by varying the temperature in a range from 20 to \(60\,{}^{\circ }\mathrm{{C}}\).

Structural characteristics and thermal stability of bimetallic Cu-Ru nanocluster

Classical molecular dynamics simulations were used to study the structural characteristics and thermodynamic stability of Cu-Ru nanoclusters of most common structural variants like decahedra, icosahedra and cuboctahedra. As a result, it is found that the three types of structures have consistent stability orders from the point of view of bimetallic elemental distributions. The Ru-core/Cu-shell structures and the eutectic-like structures are more stable than solid solution and Cu-core/Ru-shell. The formation energies of bimetallic clusters are consistently positive, which shows that they are not thermodynamically stable. All clusters including the unstable Cu-core/Ru-shell and solid solution clusters, and the relatively stable Ru-core/Cu-shell transform into eutectic-like cluster during heating process. Additionally, the large difference in melting point between pure Cu and pure Ru cause the Cu part in the formed eutectic-like clusters melt first and escape forming separate cluster in the further heating process.

Chemical Reduction Synthesis of Iron Aluminum Powders

In this study, a chemical reduction synthesis method of iron aluminum (FeAl) nano-dimensional intermetallic powders is described. The process has two stages: a salt reduction and solvent evaporation by a heat treatment at 1100∘C. The precursors of the synthesis are ferric chloride, aluminum foil chips, a mix of Toluene/THF in a 75/25 volume relationship, and concentrated hydrochloric acid as initiator of the reaction. The reaction time was 20 days, the product obtained was dried at 60 ∘C for 2 h and calcined at 400, 800, and 1100 ∘C for 4 h each. To characterize and confirm the obtained synthesis products, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) techniques were used. The results of morphology and chemical characterization of nano-dimensional powders obtained showed a formation of agglomerated particles of a size range of approximately 150 nm to 1.0 μm. Composition of powders was identified as corundum (Al2O3), iron aluminide (FeAl3), and iron-aluminum oxides (Fe0. 53Al0. 47)2O3 phases. The oxide phases formation were associated with the reaction of atmospheric concentration-free oxygen during synthesis and sintering steps, reducing the concentration of the iron aluminum phase.

SCC of X-65 Weldment Assessment in Diluted NaHCO3 Solutions with Chloride and Sulfate Ions

In the petroleum Mexican industry, most transportation of hydrocarbons is carried through underground pipelines, which are protected by coating and cathodic protection; however, pipelines could be susceptible to the stress corrosion cracking (SCC) and hydrogen embrittlement damage. In this sense, SCC assessment of API X-65 pipeline weldments in sodium bicarbonate solutions at 50 °C using slow strain rate tests (SSRT) was realized. SSR tests were complemented with hydrogen permeation and electrochemical polarization evaluations. Results showed that corrosion rate, i corr, was highest in both 0.01 M NaHCO3 and 0.01 M NaHCO3 with additions of SO4 2− ions solutions. The SCC susceptibility, in accord with the reduction in area percentage (RA%), was higher within the 0.01 M NaHCO3 and NaHCO3 with Cl− + SO4 2− ions addition solutions. The amount of hydrogen uptake for the weldment was also higher in the 0.01 M NaHCO3 solution with and without Cl− + SO4 2− ions. The SCC susceptibility of X-65 weldments in diluted NaHCO3 solutions was associated with the anodic dissolution, assisted by hydrogen entrapping within the weldment microstructure defects, as hydrogen embrittlement damage. Results were complemented by Scanning Electronic Microscopy and Energy of Dispersion of X-Ray Spectroscopy characterization.

Synthesis of Synthetic Hematite with Substituted Aluminum by Sol-Gel Method

In this work, synthetic hematite with isomorphically substituted aluminum contents were obtained by the sol-gel chemical synthesis. Nanomaterials with Fe and Al contains were obtained by the sol-gel method mixing stoichiometric mixtures of ferric chloride (FeCl3) and aluminum isopropoxide Al (OC3H7)3 at 75°C. The obtained sol-gel was dried at 60 oC followed by calcinations at 400, 800 and 1100 oC. The resulting powders were characterized by X-Ray diffraction and Scanning Electron Microscopy (SEM). Preliminary results showed α-Fe2O3 particles into amorphous Al-O-Fe structure, and the formation of alumina with sintering temperature. SEM characterization results, showed small size particle formation in the order of 100-200 nm, however nanosize particles could be improve by chemical parameters control and ultrasonic dispersion. Also SEM observation showed the formation and homogenous distribution of minority Fe-O phase particles between Al-O-Fe phase particles.