Techniques Used in Research for the Prevention of Top-of-the-line Corrosion Figure 4: Water Condensation Loop Used to Carry Out Electrochemical Measurements in a Film of Condensed Water CO2 or Argon inlet Condenser pH Thermocouple Condensation cell Cell Electrodes Thermostated water Data collection pH Condenser pH Pump Thermometer Gas outlet Graduated water collector pH electrode Condensed water Heater stirrer Reactor CO2 arrival
Acid injectiont Flow meter
Thermometer (control) Thermometer
© NACE International 2001. Source: Gunaltun and Belghazi, 2001.1
Figure 5: Illustration of an Autoclave-based Apparatus used for Evaluating the Effectiveness of Inhibitors of Top-of-the-line Corrosion
Inhibited coolant out (from waterbath)
Sampling outlet and valve
Pressurisation inlet and valve
Bracket to seal autoclave head
Teflon condensation guard
Swagelok right angle elbows with PFA ferrules
Mild steel tube sample
Inhibited coolant in (from waterbath)
Stainless steel tubing with high pressure seal in autoclave head
Temperature thermocouple linked to temperature controller
very low vapour pressure of MEG, which is too low for mass transfer via the vapour phase to achieve equilibration at the top of the line.
Other Laboratory Systems
Sometimes a laboratory test that does not try to copy the appearance of the actual physical structure, when properly understood and applied, is actually better suited to certain underlying features of the system, for example, the use of high-shear designs to simulate high flow rates in pipelines.47,48
However, other laboratory approaches
commonly used in corrosion experiments to simulate the flowing conditions in pipelines, such as rotating cylinder electrodes20,30,31 impingement electrodes,47,48
and jet cannot be adapted to represent TLC. It is
an attractive prospect to be able to apply electrochemical monitoring techniques6
to determine the instantaneous corrosion rate and even obtain additional insight into the electrochemical mechanism. However, this is not straightforward for TLC.
Sparge tube/ sampling tube
Pure water for vapour generation
Nonetheless, efforts have been made to carry out electrochemical measurements in a film of condensed water,1
Cooled commercial corrosion probes have been trialled,26
as illustrated in Figure 4. but it remains
PFA = perfluoroalkoxy. © NACE International 2009. Source: Capelli et al., 2009.43
difficult to reproduce and control the requisite conditions for TLC. A patent has been filed for a system that involves generation of wet gas in an autoclave and subsequently transferring this gas to make separate measurements in a cooled portion where condensation occurs.49
74 EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 1
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