J. Genesca

Electrochemical Behavior of API X70 Steel in Hydrogen Sulfide-Containing Solutions

As an attempt to contribute to the understanding of the cor- rosion process of steel by hydrogen sulfi de (H2S), the corro- sion behavior of an X70 pipeline steel immersed in several H2S-containing solutions is analyzed in this work. Linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques were used in order to charac- terize the corrosion behavior of X70 steel in H2S-containing solutions. Electrochemical parameters such as charge-transfer resistance, Rct, polarization resistance, Rp, and corrosion rate are presented in this work. Additionally, a comparison be- tween static and turbulent fl ow conditions was made in order to describe the corrosion behavior of X70 steel. Turbulent fl ow conditions were controlled using the rotating cylinder electrode (RCE) (at 1,000 rpm) in a saturated H2S solution.

Evaluation of the protection against corrosion of a thick polyurethane film by electrochemical noise

This paper focuses on the study of protection against corrosion by means of a thick polyurethane film. Noise resistance, Rn, calculated from a series of potential and current noise measurements, shows that electrochemical noise (EN) technique was able to monitor corrosion under coated metals even when applied at high thicknesses. By using spectral analysis, the nature of the attack on the metallic surface was determined; indeed, the characteristics of the corrosion process were determined even from the beginning of the phenomenon when the surface was exposed in a Salt Fog Chamber. It was possible to determine both how the continuous protection was given by the polyurethane film as a barrier and when the corrosion process was controlled by the appearance of pores on the barrier film. This paper seeks to establish a methodology to study highly resistant coatings.

Cementation kinetics of an industrial solution of Ag(CN)2- with granular spherical zinc in a vibrating reactor

Abstract The kinetic behavior of the cementation of an industrial solution of Ag(CN) 2 − with granulated spherical zinc in a vibrating reactor was investigated. The influence of parameters such as vibratory amplitude and frequency, cyanide and oxygen concentration, pH and temperature were studied in an intermittent state. The reaction rate was analyzed in a continuous run. Some of the significant results are the following: (1) the process takes place in two steps, the first one consisting of an instantaneous cementation in which silver concentration in solution was reduced by 54% to 78% and the second, a slower one, with a reaction order of one; (2) in batch tests, it was possible to perform the cementation at a rate of 2.49 × 10 −4 mg cm −2 s −1 with an oxyge concentration of 8 mg 1 −1 (2.5 × 10 −4 M); (3) the critical effect of the cyanide concentration in the reaction kinetics, found with different techniques in other investigations, was not observed in this study; (4) the granulated zinc was not passivated in the 77.5 min of the continuous test.

The assessment of natural atmosphere corrosivity by the use of electrochemical noise analysis

Purpose – The aim of this work is to evaluate the electrochemical noise (EN) method as a way of evaluating quickly the aggressiveness of natural atmospheres.Design/methodology/approach – Wire‐on‐bolt tests were used, which implies an exposure of at least three months of bimetallic specimens such as aluminium wire/steel bolt and aluminium wire/copper bolt (CLIMAT units). Electrochemical noise measurements (ENM) also were used.Findings – EN is a powerful tool in the assessing of aggressiveness of atmospheres in short time exposure. Statistical analyses of EN were carried out and provided clear differences between atmospheres depending on pollutants. Results of noise resistance (Rn), root mean square of current (Irms) and localization index are discussed.Research limitations/implications – The possible application of ENM to atmospheric corrosion is interesting from a practical point of view. However, more experiments are necessary in order to test a wide range of atmospheres.Practical implications – EN has p...

Comparison of Electrochemical Noise and Wire-on-Screw Technique in Simulated Marine Atmospheres

This paper shows the application of the electrochemical noise (EN) technique in the corrosion study on carbon steel in a salt-spray test. Through this electrochemical technique the resulting corrosion process is analyzed by the characteristics of the EN signal. These results, achieved with a statistical analysis of the signal, which is related to the wire-on-screw test, show the electrochemical differences in uniform, pitting, and crevice processes.

Corrosion Resistance of AA2024-T3 Coated with Graphene/Sol-Gel Films

Graphene is a two-dimensional network of carbon atoms with optimal thermal, electronic and chemical stability properties that promise different and versatile applications in various fields including the protection of metals from corrosion phenomena. For this reason in this paper graphene was employed and studied as an agent dopand incorporated into hybrid sol-gel coatings to enhance their resistance in saline media and to improve the durability of these films. Graphene was obtained by using an electrochemical method involving oxidation and reduction reactions in a sodium lauryl sulfate solution. On the other hand, the hybrid sol-gel was synthesized from the combination of inorganic and organic precursors, zirconium (IV) n-propoxide (TPOZ) and 3-glycidoxipropiltrimetoxysilane (GLYMO) respectively. In order to obtain the coating system (graphene/sol-gel) two different procedures were applied onto clean aluminum plates: a) the electrodeposition of graphene and b) the graphene-doped sol-gel coating. Differential scanning calorimetry, scanning electron microscopy and electrochemical impedance spectroscopy were used to characterize the results, which demonstrate an improvement of the corrosion properties of the films with the incorporation of graphene compounds.

Corrosion Behavior of Hybrid Sol-Gel Films Reinforced with Electrospun Nanofibers

The aim of this paper is to evaluate the efficiency of hybrid sol-gel coatings reinforced with electrospinning nanofibers doped with cerium nitrate and ceria particles to increase the corrosion properties of the coating. Poly(vinyl alcohol) solutions doped with cerium nitrate and ceria were electrospun onto clean commercial aluminum alloy AA2024-T3 plates and then coated with a hybrid sol-gel system using the dip-coating procedure. The hybrid materials synthesized via sol-gel chemistry were prepared from inorganic-organic precursors: zirconium (IV) propoxide and 3-glycidoxypropyltrimetoxysilane. The electrochemical impedance spectroscopy technique was applied to evaluate the electrochemical properties of the film whereas scanning electron microscopy and atomic force microscopy were employed to characterize the surface characteristics. The incorporation of nanofibers into the sol-gel system provides good barrier properties that increase the corrosion resistance of the aluminum at longer exposure times in saline media. This protection depends of the type of inhibitor loaded within the electrospun nanofibers.

Characterization of the Protective Properties of Hydrotalcite on Hybrid Organic-Inorganic Sol-Gel Coatings

The effect of hydrotalcite (HT) on the protection of aluminum alloy by sol-gel films was investigated by electrochemical impedance spectroscopy (EIS) and electrochemical noise measurements (ENM). S...