Avaliação da corrosão por fluxo do aço AISI 1020 em solução de NaHCO3 saturada com CO2

Orientador: Prof. Dr. Haroldo de Araújo PonteTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE. Defesa: Curitiba, 31/05/2012Inclui referênciasÁrea de concentração: Engenharia de materiaisResumo: A corrosão por CO2 é a forma predominante de corrosão encontrada na produção de combustíveis fósseis e está presente tanto na composição das jazidas de petróleo e gás natural, quanto nos processos tecnológicos de extração e refino. Os aços carbono e de baixa liga são os mais utilizados na confecção de equipamentos e tubulações, principalmente por satisfazerem os requisitos mecânicos, estruturais e de fabricação, além de serem mais viáveis financeiramente. Entretanto, estes materiais possuem baixa performance em relação à corrosão generalizada e por CO2. Este trabalho tem como principal objetivo utilizar um eletrodo cilíndrico rotativo (ECR) nas técnicas eletroquímicas comumente empregadas para a avaliação da corrosão por fluxo do aço carbono em duas condições diferenciadas de acabamento superficial. Esta avaliação foi realizada, utilizando-se como meio corrosivo uma solução de NaHCO3 0,5 M saturada com CO2. Os eletrodos de trabalho tinham formato cilíndrico e foram confeccionados em aço carbono AISI 1020. Os resultados obtidos revelaram que a formação e a passivação da camada de carbonato de ferro, é influenciada pela presença do fluxo e da rugosidade superficial do aço. A taxa de corrosão do aço atingiu valores elevados e em seguida apresentou ligeira redução com o aumento da velocidade do fluxo para a superfície mais lisa. Para a superfície com rugosidade aumentada, o fluxo provocou um aumento na taxa de corrosão com tendência a um patamar, exibindo valores maiores do que os obtidos para a superfície mais lisa, somente a partir de uma velocidade de rotação em torno de 700 rpm. Como conclusão, observou-se que o eletrodo cilíndrico rotativo é uma importante ferramenta no estudo da corrosão em presença de fluxo e que o mecanismo de corrosão sob fluxo num meio contendo CO2 envolve basicamente a formação da camada de FeCO3 de acordo com a interação permitida pela estrutura da camada limite hidrodinâmica estabelecida. Palavras-chave: Corrosão por fluxo; CO2 ; Aço-carbono.Abstract: The carbon dioxide corrosion (CO2) is the predominant form of corrosion found in the production of fossil fuels and is present both in the composition of petroleum and natural gas, as in technological processes of extraction and refining. Carbon steels and low alloy are the most used in equipment and pipes, mainly because they satisfy the requirements of mechanical, structural and manufacturing, in addition to being more financially viable. However, these materials have poor performance with respect to general corrosion and carbon dioxide corrosion. This work has as main objective to use a rotating cylinder electrode (ECR) in electrochemical techniques commonly used to assess the corrosion of carbon steel flow in two different conditions of surface finish. This evaluation was performed, using as solution with deionized water e 0.5 M NaHCO3 saturated with CO2. The working electrodes were cylindrical and were made of carbon steel AISI 1020. The results showed that formation and passivation layer of iron carbonate is influenced by the presence of flow and surface roughness of steel. The rate of corrosion of steel reached high values and then showed a slight decrease with increasing flow rate for the smoothest surface. For increased surface roughness, the flow caused an increase in rate of corrosion with a tendency to a threshold, displaying higher values than those obtained for the smoothest surface, only from a rotation rate about 700 rpm. In conclusion, it was observed that the rotating cylinder electrode is an important tool in the study of corrosion in the presence of flow and that the corrosion mechanism in a medium containing CO2 flow basically involves the formation of the layer FeCO3 according permitted by the interaction hydrodynamic boundary layer structure established. Keywords: Corrosion flow; carbon dioxide; carbon steel

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research