Carlos Joia

Hydrogen permeation studied by electrochemical techniques

Abstract In this paper impedance measurements, weight loss and hydrogen permeation tests were used to characterise the H 2 S corrosion process. In a classical permeation cell, where a steel membrane is separating two electrolytic solutions, it was seen that the detection of hydrogen diffusing through the steel is totally controlled by the anodic reactions occurring at the steel/H 2 S interface. Solutions with different aggressiveness were used to define the maximum acceptable permeation current to avoid cracks nucleation and propagation. From these tests a procedure was developed to monitor hydrogen induced cracking (HIC) in industrial plants.

Electrochemical methods in corrosion on petroleum industry: laboratory and field results

Abstract This paper presents results concerning the use of a multitask cell coupled with a semi-industrial autoclave. A very good correlation was found between electrochemical measurements performed with the multitask cell and the three-electrode probe introduced in one of the autoclaves flanges. Using the permeation technique, a short time response system was obtained with the multitask cell. The observed performance of this system was consistent with the external one attached at the flange. It was observed that neither H 2 S nor cyanide alone increase the corrosion process in the alkaline wet H 2 S environment. The coupled action of these two contaminants is necessary to increase the hydrogen permeation through the steel wall of the equipment. As a consequence of this work, the multitask cell was successfully transferred to a PETROBRAS fluid catalytic cracking light end recovery unit.

Flow Loop Study of NaCl Concentration Effect on Erosion, Corrosion, and Erosion-Corrosion of Carbon Steel in CO2-Saturated Systems

Abstract Erosion-corrosion deterioration of carbon steel in carbon dioxide (CO2)-saturated systems with sand is a problem in the oil and gas industry because the combined effects of erosion and corrosion can reduce the protection provided by iron-carbonate scale formation or inhibitors. Oil and gas production can be accompanied by the formation water (typically chloride containing brine). Some effects of chloride concentration on corrosion are not widely known, and this can result in misleading conclusions. The goal of this paper was to contribute to a better understanding of the effects of chloride concentration in CO2 corrosion. Previous studies reported in the literature and experimental and theoretical studies conducted in the present work have shown that increasing the sodium chloride (NaCl) concentration in solution has three important effects on corrosion results. First, standard pH meter readings in high NaCl concentration solutions require corrections. Second, increasing the NaCl concentration de...

Characterization and Prediction of Chemical Inhibition Performance for Erosion-Corrosion Conditions in Sweet Oil and Gas Production

The effects of sand erosion on inhibitor performance have been examined in a flow loop using an impinging jet test cell and different techniques such as long-term weight loss (WL), linear polarization resistance (LPR), potentiodynamic polarization (PDYN), 3-D profilometry, and electrochemical impedance spectroscopy (EIS). Inhibition mechanisms and the relation between inhibitor concentration and corrosion penetration rate are described by the Flory-Huggins, Frumkin, Temkin, and Langmuir adsorption isotherms. Flow loop tests indicated that sand particle erosion can decrease the efficiency of an imidazoline-based inhibitor by removing the inhibitor protective layer from the surface. Therefore, an increased concentration of inhibitor is needed during sand production to achieve the same effectiveness. It was shown that an inhibitor adsorption isotherm can be integrated into a mechanistic model for prediction of carbon dioxide (CO2) corrosion to predict CO2 corrosion rates as a function of inhibitor concentrat...

Evaluation of the Fatigue Life of High-Strength Low-Alloy Steel Girth Welds in Aqueous Saline Environments with Varying Carbon Dioxide Partial Pressures

High-strength low-alloy steel girth weld specimens were subjected to fatigue tests in saline environments saturated with different carbon dioxide partial pressures. As expected, results show that increases in gas concentration initially affect fatigue life adversely, but when higher partial pressures are associated with low stresses, a reduction in the negative impact of environmental conditions is seen. This may be related to a competition between corrosion rates and mechanisms of crack initiation and propagation. Data is presented with the aim of contributing toward the establishment of a database of results in literature which may lead to better understanding of the phenomena involved through association of these with ongoing research.

Validation Methodology of Crack Growth Measurement Using Potential Drop Method on SENB Specimens

The Brazilian pre-salt oil and gas discoveries brought technical challenges as impressive as the reserves themselves. Besides the concerns with exploration, the oil contamination with CO2, H2S and chloride enriched seawater combined with critical cyclic loads due to the relative movement of the production vessel and high water depths imposes an environment chemically and mechanically aggressive. Suitable materials to work on such harsh conditions are few and one should consider the use of special materials, such as supermartensitic and superduplex stainless steels. Although the corrosion and mechanical properties of these materials are well established, still additional crack growth data in specific environments should be provide to the subsea equipment designer. Indeed, due to the combination of cyclic loading and corrosive ambient the corrosion fatigue phenomenon is a major concern. In order to evaluate the effect of oil contaminants on the corrosion fatigue resistance of candidate materials, one should provide methods for crack growth measurement other than the use of crack gauges since those can not be used in chemically aggressive solutions. The present work aims to validate the potential drop crack growth measurement method comparing the results obtained by this technique with those produced by crack gauges on SEN(B) (Single Edge Notch Bending) specimens in air. This validation effort is essential because the ASTM E647 standard only consider the use of C(T) (Compact Tension) specimens which actually does not represents the real cracks propagation path in crucial subsea equipment, such as risers, drill pipes et cetera, that is through the wall thickness. The results produced by the two tested methodologies have an excellent agreement which makes reliable the use of the potential drop method as an alternative to monitor and measure crack growth in corrosive media.Copyright

Corrosion Fatigue Performance of Duplex 2507 for Riser Applications

Corrosion fatigue performance is of interest for high strength steels in riser applications. This work investigated the corrosion fatigue performance of 2507 duplex stainless steel for use as riser materials in environments containing high partial pressures of carbon dioxide (50–100 bar) and limited quantity of hydrogen sulfide (0–0.12 bar). The procedures developed for controlling oxygen and Fe2+ contamination as well as methods to evaluate the concentration of H2 S in the autoclave are presented. The crack growth rates and ΔKth for these materials in the pressure environments were discussed along with procedures to obtain ΔKth , when they were below 5ksi√in. Low crack growth rates in the range of 1×10−8 in/cycle were measured and the effect of sour environments was quantified. The fatigue crack growth rate in sour environments on 2507 duplex stainless steel is a 10x higher than in air.Copyright