The formation of calcium carbonate scale and the occurrence of corrosion in CO2-saturated environments in different parts of oil and gas facilities are both phenomena that have been extensively studied. However, to date, very limited work has been carried out on evaluating combined products in a combined scale/corrosion methodology. This paper presents the results from a new combined bulk jar scaling/bubble cell corrosion test. The aim of this project is to investigate the effect of two combined chemicals in a new experimental setup; to study the corrosion and scale interactions which occur simultaneously. Two combined products were assessed at 5 ppm concentration at two temperatures (60°C and 80°C) in a CO2-saturated brine. Bulk scale precipitation was monitored using a turbidity meter and the corrosion rate measurements were made using the linear polarisation resistance (LPR) technique. Scale deposition and corrosion mechanisms have been studied using surface analyses. The performance of the two combined products has also been tested to measure: (i) the increase in the induction time of the calcium carbonate formation in the bulk, (ii) the change of the morphology of the crystals and (iii) the formation of a partial protective layer on the sample.
According to this study, the new experimental method has enabled the corrosion and scale deposition on pipeline steel (X65) and the bulk precipitation process to be studied simultaneously. Detailed scale deposition mechanisms on the material surface in the presence of corrosion processes and combined products are addressed from this study.