A systematic scale-corrosion study of a combined inhibitor in scale-corrosion environment via experimental design

The scale-corrosion performance of combined inhibitors for oilfield application has been assessed under scale-corrosion conditions in a newly developed bubble cell/jar test. The general corrosion of carbon steel X65, localised corrosion, bulk scale precipitation and surface scale deposition have been determined by various techniques (Linear Polarisation Resistance, contact 3D profiler, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX), X-ray diffraction (XRD) and Turbidity-meter). The parameters used in this study are temperature, supersaturation ratio with respect to calcium carbonate and addition of different formulation of combined inhibitor derived from the single components at different concentrations. A full two-level factorial experimental design method was applied to study the individual effects of single components of combined inhibitor as well as their interactive effects on the scale and corrosion processes. The analysis shows that souring agent (component of combined inhibitor) has the greatest effect on general corrosion while the scale component has the greatest effect on bulk and surface scaling as expected. The paper discusses the interactions between the scale and corrosion processes as well as the interactions between the inhibitor components.