Raymundo Case

Study of Environmentally Assisted Cracking of Duplex Stainless Steels as a Result of the Presence of Sigma Phase

Abstract Offshore operations worldwide recently reported the presence of improperly heat-treated 2205 (UNS S32205) and 2507 (UNS S32750) duplex stainless steel (SS) pipe fittings with varying volum...

High Temperature Corrosion Studies in Simulated SAGD Produced Fluids

Heavy oil extraction using steam flooding methods, such as steam assisted gravity drainage (SAGD), has been used for several decades; yet no severe corrosion damage has been reported despite the pr...

Stochastic Approach to the Modeling of CO2 Corrosion

Corrosion assessment is an integral part of predictive maintenance estimations. In such cases, a risk-based approach yields results that can easily be implemented. The results from deterministic (mechanistic or semi-empirical) corrosion models are valid for a “general” rate of dissolution based on the mass and charge balance of an exposed surface; however, they have a limited application in the quantitative assessment of corrosion-related damage. This work introduces a general stochastic algorithm for calculating the carbon dioxide (CO2)-related distribution of corrosion damage penetration at a given time interval, coupled with corrosion rates predicted by conventional deterministic models. The model is validated by directly comparing the simulation output with actual inspection results from several real cases. The results obtained indicate that the stochastic modeling of CO2 corrosion based on mechanistic principles allows the assessment of failure probability in a quantitative manner. Additionally, the ...

Analysis of Pit Stability in Type 316L Stainless Steel Exposed to H2S-Saturated Dilute Chloride Solutions Above the Critical Pitting Temperature

Abstract This study examines the effect of hydrogen sulfide (H2S) on the transition from metastable to stable propagating pits using Type 316L (UNS S31603) steel in brines with Cl− concentrations of 10−3 M to 2 × 10−2 M at 75°C and 150°C. The potentiostatic tests were performed at discrete intervals of 50 mV from the recorded open-circuit potential (OCP) to 300 mV above the OCP. The results based on analysis of the chrono-amperometric transients suggests that the transition to stable pit growth is hindered by H2S saturation at both temperatures. The comparison of the experimental results with similar tests in an acidified control brine (without H2S saturation) indicates that the effect of H2S in the promotion of pit metastability is associated with the diffusion of H2S to the bottom of the cavity. This increases the net anodic current by irreversibly forming metallic sulfides, which, in turn, affect the pits anolyte by reducing the metal salt concentration. The consequence of this effect is that small pi...