The aim of this research was to study the effectiveness of typical oilfield corrosion inhibitors in controlling internal corrosion of welded X65 pipeline steel in brines saturated with carbon dioxide at one bar pressure, under dynamic flowing conditions, at a range of temperatures. A rotating cylinder electrode (RCE) apparatus was designed to allow steel from the weld metal, heat affected zone (HAZ) and parent material to be galvanically coupled and tested in high shear stress conditions. In producing the RCE, the three regions of the weld were identified by optical metallography and samples of each were machined to produce cylindrical electrodes, which were mounted on a motor driven shaft. Electrical connections were made to the three electrodes via a high quality slip-ring assembly. The galvanic currents flowing between the regions of the weld were recorded using zero-resistance ammeters and their self-corrosion rates were found by uncoupling the electrodes and performing polarization resistance measurements. Both the galvanic currents and the self-corrosion rates were found to increase with the shear stress, as the rotational speed of the RCE was increased. The total corrosion rate of each weld region was assessed from the sum of the self-corrosion and galvanic contributions. In most cases, the weld metal and HAZ were shown to be cathodic to the parent material and this was considered to be a desirable situation as localized corrosion of the weld was minimized. However, in some circumstances a current reversal took place, which resulted in accelerated corrosion of the weld. These findings are explained in terms of the protective nature of the films that form on each region of the weld.
Inhibition of weld corrosion in flowing brines containing carbon dioxide
Inhibition der Schweißstahl-Korrosion im strömenden, Kohlenstoffdioxid-haltigen Salzwasser
2008
14 Seiten, 11 Bilder, 1 Tabelle, 5 Quellen
Aufsatz (Konferenz)
Englisch
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