Effect of Water on the Stress Corrosion Cracking Behavior of API 5L-X52 Steel in E95 Blend

The effect of water content (0.5%, 1%, 2%, 5%, 10% y 20 V%) in E95 blend (5 V% gasoline – 95 V% ethanol) on the stress corrosion cracking (SCC) susceptibility of X-52 carbon steel was investigated. Slow strain rate tests (SSRT) coupled with electrochemical noise measurements (ECN) were carried out using a strain rate of 1 X 10-6 s-1. In general, scanning electron microscopy (SEM) observations on fracture surfaces showed a ductile behavior. However, secondary cracking was only observed for specimens exposed to solution containing up to 2 V% water. ECN gave indication of a likely localized corrosion process occurring at low water concentrations, whereas for water content above 2 V%, a uniform corrosion process seems more likely to occur. In addition, the material response immersed into the various solutions was investigated by using linear polarization resistance (LPR) measurements, weight loss and pH measurements. Reasons to explain the behavior found are discusse

Mechanosynthesis of MFe 2

Adsorption of Pb(II) from aqueous solution using MFe2O4 nanoferrites (M = Co, Ni, and Zn) was studied. Nanoferrite samples were prepared via the mechanochemical method and were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), micro-Raman, and vibrating sample magnetometry (VSM). XRD analysis confirms the formation of pure single phases of cubic ferrites with average crystallite sizes of 23.8, 19.4, and 19.2 nm for CoFe2O4, NiFe2O4, and ZnFe2O4, respectively. Only NiFe2O4 and ZnFe2O4 samples show superparamagnetic behavior at room temperature, whereas CoFe2O4 is ferromagnetic. Kinetics and isotherm adsorption studies for adsorption of Pb(II) were carried out. A pseudo-second-order kinetic describes the sorption behavior. The experimental data of the isotherms were well fitted to the Langmuir isotherm model. The maximum adsorption capacity of Pb(II) on the nanoferrites was found to be 20.58, 17.76, and 9.34 mg·g−1 for M = Co, Ni, and Zn, respectively

Corrosion behavior of AISI 409Nb stainless steel manufactured by powder metallurgy exposed in H2SO4 and NaCl solutions

Powder metallurgy is an effective method for manufacturing stainless steel parts of high quality and accuracy at low cost. However, the use of sintered stainless steels is limited due to their low density, which deteriorates their corrosion resistance. The aim of this study was to determine the corrosion behavior of AISI 409Nb stainless steel specimens sintered with different contents of boron in a hydrogen atmosphere. Boron was added for promoting the formation of a liquid phase during sintering at 1150 °C, thereby achieving a reduction of porosity and increase in density, which is necessary to improve corrosion resistance. The electrochemical techniques of linear polarization resistance (LPR) and electrochemical noise (EN) were used to determine the corrosion behavior of samples with and without additions of boron after immersion in two solutions, 0.5M H2SO4 and 0.5M NaCl. The corrosion rates and the possible corrosion mechanisms in the sintered samples were determined. The results indicate that the samples with boron additions are more prone to corrosion due to chromium carbide precipitation

High Temperature Corrosion of Nickel in NaVO3-V2O5 Melts

Many alloys used at high temperature in industrial processes are Ni-based and many others contain it in appreciable quantities, so it is of interest to evaluate the performance of pure nickel in order to determine the behavior of its alloys once the elements responsible for their protection have been depleted due to accelerated corrosion processes in the presence of vanadium-rich molten salts. Due to this, this work presents the study of Ni behavior in NaVO3-V2O5 mixtures at different temperatures. The behavior of pure nickel was determined by both electrochemical and mass loss measurements. The results show that the aggressiveness of the vanadium salts is increased by increasing both the V2O5 content and temperature. V2O5 addition considerably increases the current densities of the anodic and cathodic reactions. The corrosion process of Ni is modified due to the presence of its corrosion products, and its presence increases the activation energy by at least one order of magnitude. Although nickel shows a high reactivity in vanadium-rich salts, its reaction products are highly stable and protect it from the corrosive medium because the corrosion reactions trap the vanadium and block the migration of nickel ions

Parameter Studies on High-Velocity Oxy-Fuel Spraying of CoNiCrAlY Coatings Used in the Aeronautical Industry

The thermal spraying process is a surface treatment which does not adversely affect the base metal on which it is performed. The coatings obtained by HVOF thermal spray are employed in aeronautics, aerospace, and power generation industries. Alloys and coatings designed to resist oxidizing environments at high temperatures should be able to develop a surface oxide layer, which is thermodynamically stable, slowly growing, and adherent. MCrAlY type (M = Co, Ni or combination of both) coatings are used in wear and corrosion applications but also provide protection against high temperature oxidation and corrosion attack in molten salts. In this investigation, CoNiCrAlY coatings were produced employing a HVOF DJH 2700 gun. The work presented here focuses on the influences of process parameters of a gas-drive HVOF system on the microstructure, adherence, wear, and oxygen content of CoNiCrAlY. The results showed that spray distance significantly affects the properties of CoNiCrAlY coatings

Mechanosynthesis of MFe2O4 (M = Co, Ni, and Zn) Magnetic Nanoparticles for Pb Removal from Aqueous Solution

Adsorption of Pb(II) from aqueous solution using MFe2O4 nanoferrites (M = Co, Ni, and Zn) was studied. Nanoferrite samples were prepared via the mechanochemical method and were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), micro-Raman, and vibrating sample magnetometry (VSM). XRD analysis confirms the formation of pure single phases of cubic ferrites with average crystallite sizes of 23.8, 19.4, and 19.2 nm for CoFe2O4, NiFe2O4, and ZnFe2O4, respectively. Only NiFe2O4 and ZnFe2O4 samples show superparamagnetic behavior at room temperature, whereas CoFe2O4 is ferromagnetic. Kinetics and isotherm adsorption studies for adsorption of Pb(II) were carried out. A pseudo-second-order kinetic describes the sorption behavior. The experimental data of the isotherms were well fitted to the Langmuir isotherm model. The maximum adsorption capacity of Pb(II) on the nanoferrites was found to be 20.58, 17.76, and 9.34 mg·g−1 for M = Co, Ni, and Zn, respectively