Estudo da resistência à corrosão das superligas de níquel AWS ERNiCrMo-3 e AWS ERNiCrMo-4 para utilização em soldas de tubulações na indústria de óleo e gás

Abstract

In the oil and gas extraction and transportation industry, one of the main technological challenges is the development of new materials capable of operating in ultra-deep wells under high pressures and temperatures. Critical operating conditions, such as the presence of salts, CO2, O2, and H2S, underscore the need for materials with high resistance. Under these conditions, one of the major issues is the corrosion of materials, which can lead to accidents with significant environmental damage and even loss of human life. Therefore, rigorous control of corrosive action on metals is of essential economic, technical, and environmental importance. Specifically in the case of pipelines, weld points require special attention as they are more susceptible to corrosive processes. Given the demand for new materials, this study aims to investigate the corrosion resistance of nickel superalloys used as pipeline welds in the oil and gas industry. Nickel superalloys stand out in the petrochemical sector due to their excellent mechanical properties, high corrosion resistance in aggressive environments, and superior wear resistance, especially in high-temperature settings. The study of corrosion resistance of different mixtures of AWS ERNiCrMo-3 (Inconel 625) and AWS ERNiCrMo-4 (Hastelloy C276) alloys, used as coatings in oil and gas extraction and transportation pipelines, is necessary because these materials exhibit a combination of good mechanical properties, excellent weldability, and corrosion resistance in various environments and prolonged exposure to aggressive conditions. However, there is limited literature on their behavior when welded and mixed, as well as on the influence of thermal treatments following welding. The investigation will employ electrochemical techniques such as Open Circuit Potential (OCP), Linear Polarization Resistance (LPR), and Electrochemical Impedance Spectroscopy (EIS) in a 3.5 M NaCl electrolyte solution at atmospheric pressure and room temperature (25 ºC), both with and without the presence of CO2. The results indicate a lower corrosion resistance of these materials in CO2-saturated environments. Samples of alloy C treated at 950 ºC for 50 hours exhibited the lowest combination of critical and passive current densities.