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Prediction of Corrosion Inhibitor Performance Using Simulated CO2/H2S Environmental Autoclave and Flowloop Tests - I
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Flowloop Test ApparatusAs a result of budget and personnel restraints, it was
necessary and more economically attractive to contract the
flowloop testing to an outside laboratory than to design and
construct the flowloop test apparatus required as well as commit
the number of personnel necessary to perform the testing. The
consulting laboratory that did our earlier high pressure-high
temperature flowing autoclave testing was selected to perform the
flowloop testing. The apparatus used was theirs and is diagramed
in Figure 1. The apparatus test
parameters included: 300 F. (149 C.); pp CO2 of 75
psia (0.5 Mpa); pp H2S of 0.075 psia (0.5 Kpa); 10
percent depolarized kerosene; 90 percent Synthetic Brine.
The flowloop was designed to produce the same magnitude of wall
shear stress in the pipeline due to laminar flow and in the
turbulent flow region of the impingement electrode for a given
liquid flow rate in the pipeline. Additionally, it provides for
simulation of complex mixed brine fluids and the effects of
dissolved acid gas at partial pressures similar to those in the
pipeline.
The diagram indicates the location of the test electrodes in the
flowloop apparatus. In all cases linear polarization resistance
(LPR) probes were used and instantaneous corrosion rates were
determined using electrochemical techniques (ASTM G59) and the
average corrosion rate using weight loss techniques (ASTM G). The
type and metallurgy of the LPR are located in the apparatus as
indicated in Figure 1:
Location LPR Probe Description Metallurgy
1. Laminar Flow Electrode X-65
2. Laminar Flow Electrode 0.5 CrX-65
3. Impingement Electrode X-65
4. Reservoir Electrode X-65
5. Reservoir Electrode 0.5CrX-65
Alloy analyses of the LPR probe electrode materials are shown in Table 5. The test electrodes in the reservoir
were standard 0.25 inch (0.64 cm) diameter and 1 inch (2.54 cm)
long rods. In the laminar region, tubular specimens of 0.5 inch
(1.27 cm) I.D. were used. The target specimen in the turbulent
region was a cross-section of a tubular specimen (0.202 inch I.D.
and 0.404 inch O.D.) press fit into the peek specimen holder. All
the specimen surfaces were polished to 600 grit finish with SiC
paper and degreased before mounting in the apparatus.
The test for calibration of the experimental set-up was performed
using AISI 1018 carbon steel in a synthetic sea water
environment.
Figure 1 Consulting Laboratory Flow Loop Apparatus ALLOY | HEAT | Al | C | Cr | Cu | Fe | Mn | Mo | Ni | P | S | Si | Ti | other | 5lx65 | d134 |
| 0.07 |
|
|
| 1.26 |
|
| 0.014 | 0.011 | 0.24 |
| Cb-0.033; V-0.04 | 5L0.5CrX60 | a-50 | 0.035 | 0.07 | 0.55 |
|
| 1. 27 |
|
| 0.012 | 0.010 | 0.24 |
| Cb-0.033 |
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