Resumo em Inglês:

Saturation of acidic gases in seawater, resulting from deepwater activities in the oil and gas industry, can promote detrimental effects on the internal metallic sheath of pipelines due to an eventual failure of the outer sheath. Failures in the tensile armor typically occur in a confined space due to the low volume of electrolyte, i.e. seawater, in comparison to the exposed surface area of the steel. This condition promotes the supersaturation of several species in this environment. This study was conducted to investigate the complex chemistry and electrochemical mechanism involved in CO2 corrosion in confined spaces. The aim is to elucidate the impact of low CO2 partial pressures, either 1 or 3 bar, on the supersaturation of species as well as the formation of a solid FeCO3 film onto the alloy surface and evaluate its protectiveness degree. The data obtained suggests the presence of a more protective layer associated with a pressure of 3 bar, represented by a continuous and compact FeCO3 film approximately 26.54 µm thick. Despite the faster growth of FeCO3 films at 1 bar, they appear to exhibit non-protective properties, as observed through SEM analyses, with a discontinuous layer measuring about 20.86 µm in thickness.

Resumo em Inglês:

Durability and corrosion resistance are essential requirements in the development of aerospace components, and the optimization of anodizing processes stands out as an effective strategy to enhance the corrosion performance of aluminum alloys used in this sector. In this context, the present study provides new insights into the effect of the presence of different carboxylic acids (oxalic, citric, and succinic) in a sulfuric acid-based anodizing electrolyte on the corrosion resistance of the AA2024-T3 aluminum alloy. The anodic oxide films were characterized using microscopy and electrochemical analyses to assess their morphological and corrosion-resistant behavior. The results indicated the formation of oxide films with different surface morphologies, uniform thickness ranging from 16.7 to 23.8 µm, and satisfactory protection against corrosion in NaCl media (0.1 mol.L-1), especially with regard to treatment with oxalic acid (OSA), which, compared to other treatments with carboxylic acids (citric – CSA, and succinic – SSA) and the standard treatment (sulfuric acid – SA), maintained the highest protective performance of the coating over 21 days of immersion.

Resumo em Inglês:

Zirconium-based conversion coatings provide an environmentally friendly, chromate-free alternative to traditional phosphating and chromating processes for enhancing the corrosion protection of metal substrates. This study investigates the formation and characterization of zirconium-based conversion coatings (Zr-CC) on AA3105-H16. The coatings were produced by immersion in an hexafuorozirconic acid (H2ZrF6) solution and characterized using SEM-FEG, SEM/EDS, and Raman spectroscopy. Considering that the incorporation of organic and/or inorganic additives can enhance the anticorrosive performance of Zr-CCs, electrochemical techniques were employed to assess the influence of Cu2+ ions on corrosion resistance in a sodium chloride medium. The results indicate that, under the tested conditions, Cu2+ ions act as precursors for film formation, increasing the open-circuit potential and decreasing the coating formation time. However, coatings formed in the presence of Cu2+ ions exhibited lower corrosion resistance, revealing a detrimental effect on anticorrosive performance.

Resumo em Inglês:

The formation of scale deposits in pipelines within the oil and gas sector is a recurring challenge that impacts operational efficiency and incurs various associated costs. Understanding the processes of mineral formation and dissolution that contribute to these deposits is essential for the implementation of effective control and mitigation strategies. This study used thermodynamic simulations to predict mineral species present in inorganic scale deposits in saline water systems within the oil and gas industry in order to provide background knowledge for future scale inhibition studies. To this end, the software The Geochemist’s Workbench was employed to construct stability diagrams, taking into account thermodynamic parameters such as pH, temperature, and pressure, through focusing on a high-bicarbonate, low-sulfate formation water, a common but challenging scenario where carbonate scaling dominates. Through the thermodynamic simulations, the software suggested the precipitation of Witherite (BaCO3), Strontianite (SrCO3), and Dolomite (CaMg(CO3)2), which were not expected for the present scenario, due to the low concentrations of Ba, Mg and Sr. Thus it was suggested that such results did not take into consideration the precipitation kinetics and the amount of crystalized material. In addition to the simulations, the systems were analyzed through static tests, and the resulting precipitates were characterized using optical microscopy, X-ray diffraction, and thermal analysis. The thermodynamic simulation results were compared with the experimental data, enabling an assessment of the consistency between the theoretical models and the observed results.

Resumo em Inglês:

The operational conditions for oil and gas production frequently change. Consequently, equipment and pipes originally specified for milder conditions may no longer meet the standards requirements. This study addresses the safety of maintaining AISI304 and 316L flexible pipe carcasses in sour service with high chloride content. A rigorous laboratory testing program was carried out with specimens machined from field-removed carcass sections, designed to reproduce a more aggressive scenario than current operational conditions. The methodology employed the U-bend technique to apply stress in the plastic regime, combined with crevice formers, and included welded samples to study the effect of sensitization. The results confirmed that sensitization and cold work influences corrosion susceptibility of both steels. Similar performance was observed to AISI304 and AISI316L in high chloride and H2S environments. This good field performance is attributed to the influence of H2S, in concentrations above 100ppm. The formation of a dense sulfide layer is favored, constraining pit development. A new unified operational limit was established for AISI304 and AISI316L carcass: high chloride environment, 60oC and 1≤[H2S]≤5% in gas mixture. The experimental data provides essential criteria for life extension and reuse of flexible assets under conditions not specified on current standards.

Resumo em Inglês:

Process and inspection data are essential for monitoring the aggressiveness of the environment and identifying risk situations. However, the diversity and amount of data make their analysis difficult. In this context, the use of machine learning to process these datasets in an integrated manner represents a significant advancement in understanding corrosion, especially under field conditions. Artificial intelligence can help create more accurate models, contributing to predicting the service life of existing systems. This work is based on the study of machine learning techniques to develop a data‑processing methodology capable of capturing the complexity and synergies occurring in real systems in a reliable way. We used the Python scikit‑learn package to simulate a dataset with 354 laboratory tests reproducing oil‑industry conditions. After analyzing the dataset, a decision‑tree algorithm was selected, with split nodes based on possible corrosion mechanisms, directing the data to different analysis methods. Data classification was performed using corrosion knowledge available in the literature and the authors’ experience. Modeling was executed by fragmenting the matrix according to ranges of variables such as test duration, temperature, shear stress, and CO2, H2S, and salinity concentrations. A quadratic error (R2) higher than 0.9 was obtained, indicating good correlation between the proposed model and the analyzed data.