Surface Response Design to Study the Effect of Low Oxygen Levels On Carbon Dioxide Corrosion Environments

The goal of this study was to simulate oxygen (O₂) contamination and determine its impact on an aqueous carbon dioxide (CO₂) environment.  The study used a quadratic model in a surface response experimental design to determine the effects of oxygen and five other variables on the corrosion of carbon steel in a CO₂ environment.  Surface response design was used to optimize the number of tests needed to determine statistical significance of the six experimental factors.  Temperature (25 to 66°C), sodium chloride composition (0.1 to 1.0 wt%), brine-hydrocarbon ratio (50 to 75 wt%), electrode surface preparation (media blasted or acid etched), oxygen inhibitor concentration (0 to 100 ppm), and headspace oxygen level (100 to 10,000 ppm) were varied in a corrosion test design matrix.  Separate from the corrosion measurements, an oxygen sensor was used to measure the concentration of oxygen in the hydrocarbon and brine phases.  The oxygen measurements were compared to the corrosion rate (CR) measurements to determine the effect of oxygen contamination on the corrosiveness of the environment.