Mariano Kappes

Comisión Nacional de Energía Atómica | cnea · Department of Materials

Existing natural gas pipelines provide an economic alternative for the transport of hydrogen (H 2 ) in an envisioned hydrogen economy. Hydrogen can dissolve in the steel and cause hydrogen embrittlement (HE), compromising pipeline structural integrity. HE causes subcritical cracking, decreases ductility and fracture toughness, and increases the fat...

In the first part of this paper, trenches were reported for Ni-containing steels tested using the slow strain rate test (SSRT) method in H2S-containing environments at the open-circuit potential (OCP). Trenches are deep elongated pits, and their appearance is more similar to small blunt cracks. These features can develop a sharp sulfide stress crac...

The nickel content in low alloy steels (LAS) for oil and gas exploration and production is limited to a maximum of 1 wt.% according to ANSI/NACE MR 0175/ISO 15156. This restriction is imposed to avoid sulfide stress cracking (SSC) in sour (H2S-containing) environments. In this work, the effect of Ni on SSC of LAS was studied independently of other...

Blending hydrogen in existing natural gas pipelines compromises steel integrity because it increases fatigue crack growth, promotes subcritical cracking and decreases fracture toughness. In this regard, several laboratories reported that the fracture toughness measured in a hydrogen containing gaseous atmosphere, K IH , can be 50% or less than K IC...

The double loop electrochemical potentiokinetic reactivation (DL-EPR) method estimates the degree of sensitization (DOS) in stainless steels with ir /ia , the ratio of peak current densities during reactivation (reverse) and activation (forward) scans. Beyond sensitization level, other metallurgical variables, like inclusion content and cold work,...

This work describes an inexpensive holder for corrosion experiments, developed to avoid crevice corrosion during pitting corrosion tests of corrosion-resistant alloys. It is based on a flooded gasket, incorporated in a Stern-Makrides sample holder. Unlike the Avesta cell designed by Qvarfort, the proposed sample holder does not require a pump. The...

Surface trenches are described as elongated pits or blunt cracks with a large depth (d) to width (a) ratio that occur as the result of an environmentally and stress-assisted damage. Trenches may represent a transition from pits to cracks in stressed carbon and low alloy steels specimens when exposed to H2S-containing solutions under certain experim...

Alloys 600 and 800 exhibited stable pitting corrosion in 1 M NaCl plus thiosulfate deaerated solutions at the open circuit potential (OCP) and room temperature. Alloy 690 exhibited only metastable pitting. Stable pitting, stable passivity or metastable pitting were identified by observing features in the OCP vs. time transients and by analysis of e...

Hydrogen permeation experiments were performed in quenched and tempered (Q&T) low alloy steels with varying Ni contents exposed to 1 bar H 2 at 30, 50 and 70C. From the analysis of build-up and decay transients, it is concluded that the permeation coefficient, the apparent diffusion coefficient (D app ) and the concentration of hydrogen in interstiti...

In this study, six flexible pipe steel armor wires used in oil and gas transportation are characterized, and their hydrogen diffusion coefficients and hydrogen uptakes are measured using an electrochemical hydrogen permeation technique. The wires have ferritic–pearlitic microstructures with round, lamellar, or partially lamellar carbides and the sh...

In accordance with Annex A of ANSI (1) /NACE (2) MR0175/ISO (3) 15156-2, low-alloy steel (LAS) components for oil and gas (O&G) are acceptable if they contain less than 1 wt.% Ni. As an alloying element in steels, nickel improves low-temperature toughness and hardenability and does not promote the formation of carbides that could retain hydrogen in...

Low potential pitting corrosion (LPPC) of alloys 690 and 800 (UNS N06690 and N08800) was studied in neutral solutions, containing chloride ion from 0.1 to 1 M and thiosulfate ion from 5x10-5 to 10-3 M. LPPC occurred close to the corrosion potential (-0.25 VAg/AgCl) by a synergic effect of the chloride and thiosulfate ions. The threshold concentrati...

Fluorides, bromides, and iodides, despite being less common than chlorides, are present in various environments of industrial relevance. Stainless steels suffer pitting corrosion in solutions of all halides except fluorides, which can be understood considering that fluoride is the anion of a weak acid. The aggressiveness of the rest of the halides...

The presence of thiosulfate ions in chloride solutions may produce pitting corrosion of UNS N06690 (alloy 690) and UNS N08800 (alloy 800). These alloys are the current options for steam-generator tubing of nuclear reactors. Two submodes of pitting corrosion in chloride plus thiosulfate solutions were observed in both alloys: low potential pitting c...

Pitting corrosion of alloys 600, 690, and 800 (UNS N06600, N06690 and N08800) was studied in 1 M NaCl solution with different concentrations of thiosulfate (S2O32-). Alloys exhibited vastly different electrochemical behavior, depending on the S2O32- concentration and chromium content of the alloy. Alloy 600 exhibited a breakdown and repassivation p...

RESUMEN Los aceros de baja aleación son ampliamente utilizados en la industria del gas y petróleo. La incorporación de Ni en estos aceros mejora la tenacidad a la fractura a bajas temperaturas y la templabilidad, con bajo impacto negativo en la soldabilidad. Sin embargo, la norma ISO 15156-2 restringe su uso hasta un máximo de 1 % en peso, exigiend...

Aluminum alloy UNS A95052 (AA5052) is very attractive for desalination applications because of its good corrosion resistance in seawater at temperatures up to 125°C, low cost, good thermal conductivity, and non-toxicity of its corrosion products. The pitting corrosion potential, Epit, and the pit repassivation potential, Er,pit, of AA5052 were meas...

Super duplex stainless steels are ferritic-austenitic stainless steels with 25 wt% Cr and a pitting resistance equivalent (PRE) ≥ 40. Even though other elements, such as Cr and Mo, have been studied in much more detail than W, research has shown that an optimal composition exists, in which W in solid solution improves localized corrosion resistance...

Alloys UNS N06600, N06690 and N08800 used for steam generator tubes are prone to pitting corrosion in aqueous chloride-thiosulfate solutions. Pitting corrosion was studied in 0.1 to 1 M chloride solutions with additions of thiosulfate ranging from 10-4 M to 10-2 M, at room temperature. The alloys were tested in solution annealed and thermally aged...

Nickel additions to low alloy steels improve mechanical and technological properties. However, Part 2 of ISO Standard 15156 limits the nickel content to a maximum of 1 wt% in oil and gas environments containing H2S because of controversial concerns regarding sulfide stress cracking. The objective of this work was to investigate the effect of nickel...

Nickel alloy 690 (UNS N06690) is one of the current choices for nuclear power plant steam generator tubing. The severity of certain stress corrosion cracking submodes in Ni-Cr-Fe alloys, such as Alloy 690, may be a function of the alloy sensitization condition. Sensitization results from chromium carbide precipitation at or near grain boundaries wh...

Nickel base alloys 600 690 and 800 are used in steam generator tubing of nuclear reactors. These alloys can suffer pitting corrosion problems in chloride solutions in the presence of thiosulfate in a similar manner to what was studied in more detail in stainless steels. Thiosulfate may be present in the environment to which these alloys are exposed...

Minimizing contamination of control treatments in microbiologically influenced corrosion (MIC) studies is of critical importance. Metal sterilization procedures should not alter the surface nor affect the inherent susceptibility of the metal to corrosion while adequately deactivating biological activity. However, there is no consensus in the litera...

Crevice corrosion affects the integrity of stainless steels used in components exposed to seawater. Traditionally, crevice corrosion testing involves the use of artificial crevice formers to obtain a critical crevice potential, which is a measure of the crevice corrosion resistance of the alloy. The critical acidification model proposed by Prof. J....

Low alloy steels (LAS) are extensively used in oil and gas (O&G) production due to their good mechanical properties and low cost. NACE MR0175/ISO15156 specifies a maximum of 1wt% nickel (Ni) in LAS. That is, the NACE/ISO restriction excludes a significant number of high-strength and high-toughness alloys, such as Ni-Chromium (Cr)-Molybdenum (Mo), N...

Low-alloy steels (LAS) are extensively used in oil and gas (O&G) production due to their good mechani- cal properties and low cost. Even though nickel improves mechanical properties and hardenability with low penalty on weldability, which is critical for large subsea compo- nents, nickel content cannot exceed 1-wt% when used in sour service app...

The objective of this work was to develop the foundation for an interactive corrosion risk management tool for assessing the probability of failure of equipment/infrastructure as a function of threats (such as pitting corrosion and coating degradation) and mitigation schemes (such as inhibitors and coatings). The application of this work was to ass...

Low-alloy steels (LAS) are extensively used in oil and gas (O&G) production due to their good mechanical properties and low cost. Even though nickel improves mechanical properties and hardenability with low penalty on weldability, which is critical for large subsea components, nickel content cannot exceed 1-wt% when used in sour service application...

Argentina. *** General Electric, Oil and Gas, Sandvika, Norway. (1) UNS numbers are listed in Metals and Alloys in the Unified Num-bering System, published by the Society of Automotive Engineers (SAE International) and cosponsored by ASTM International. ABSTRACT Stress corrosion cracking of the Mg-Al-Zn AZ31B (UNS M11311) alloy was studied in sodiu...

Magnesium and magnesium alloys are susceptible to stress corrosion cracking in various environments, including distilled water. There is compelling evidence to conclude that SCC is assisted, at least in part, by hydrogen embrittlement. This paper reviews the thermodynamics of the Mg-H system and the kinetics of hydrogen transport. Aspects of magnes...

Corrosion fatigue crack growth rates were obtained for X65 pipeline steel in acid brines containing thiosulfate (S 2O 32-) or hydrogen sulfide (H 2S). Samples were exposed for 72 h at the open-circuit potential to allow bulk hydrogen charging. The corrosion fatigue crack growth rate increased with partial pressure of H 2S and correlated with the st...

The corrosion rate of carbon steel in acidified, thiosulfate-containing brines increased with thiosulfate content. Thiosulfate also increased the rate of cathodic and anodic reactions, as measured in polarization curves obtained shortly after immersion of the electrode. Current from iron dissolution was balanced by hydrogen evolution and reduction...

Corrosion tests with gaseous H2S require special facilities with safety features, because H2S is a toxic and flammable gas. The possibility of replacing H2S with thiosulfate (S2O32-), a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H2S solutions was first proposed by Tsujikawa in 1993. H2S production was...

The possibility of simulating H2S bubbling with additions of thiosulphate, S2O32-, during corrosion fatigue studies is evaluated in this paper. First, the range of partial pressure that is possible to simulate with S2O32- additions is estimated by measuring the kinetics of H2S production during open circuit corrosion of steels in acidified, S2O32--...

This work evaluates the possibility of replacing hydrogen sulfide (H 2S) with thiosulfate anion (S2O32- ) in sour corrosion fatigue studies. H2S increases the corrosion fatigue crack growth rate (FCGR) and can be present in carbon steel risers and flowlines used in off-shore oil production. Corrosion tests with gaseous H2S require special facilitie...

Corrosion protection of carbon steels by organic coatings is dependent on a good adhesion between coating and substrate. In this work the blister test method was used to study the adhesion of a pressure sensitive tape applied on carbon steel. Deionized water was used to pressurize a blister formed by the tape covering a through-hole in the steel su...

The corrosion behavior of different tempers of two aluminum alloys, AA7050 and an experimental Al-Mg-Cu-Si alloy, was studied in NaCl solution by anodic polarization and scanning electron microscopy and was correlated with differences in the microstructure. Potentiodynamic polarization experiments were performed on samples from the exact sheets use...