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55 NACE INTERNATIONAL: VOL. 56, NO. 5 MATERIALS PERFORMANCE MAY 2017 measured by the EFM and UT scan. The average metal loss detected by UT scan was ~0.36 mm (14 mils) for 16 selected locations and the calculated average corrosion rate was 2.3 mm/y (90 mpy/y). With this acid environment, the results of the EFM system were similar to the UT readings. The aver- age metal loss was ~0.257 mm (10.1 mils) and the average corrosion rate was 1.82 mm/y (71.7 mpy). Therefore, the difference between UT and EFM in terms of metal loss was ~0.1 mm, meaning that the EFM sys- tem's data accuracy and reliability can be more obvious in aggressive corrosion envi- ronments. Figure 6 shows Spool 3 after the experiment. UT locations for selected areas are marked. Figure 7 shows the final metal thickness detected by EFM for Spool 3 after the experiment. In this part of the test, the EFM showed the ability to detect the changes in metal thickness. Therefore, this study con- firmed that the EFM system responded to the reduction in metal thickness when the reduction in pipe metal thickness was higher than 0.2 mm. Figure 8 exhibited the results of six locations measured by EFM and U T. U T readings were higher than EFM readings in Locations 2 through 4 by 30 to 50%, while at Locations 1, 5, and 6, EFM read- i n g s w e re sli g h tly h i g h e r th a n U T by almost 7 to 20%. Conclusions An EFM system was evaluated under three conditions to assess its sensitivity and reliability in measuring metal loss. The EFM results under each condition were compared with the UT results. It can be concluded from this study that the EFM technology can merely respond to metal thickness changes when the reduction of the metal thickness is higher than 0.2 mm (7.9 mils). A UT scan showed the ability to detect minor metal thickness changes even if the changes are <0.2 mm. Acknowledgments The authors would like to thank Saudi Aramco Research & Development Center management and the Inspection Depart- ment for the full support that was provided to complete this project. They also thank FIGURE 6 Spool 3 photo after the experiment with UT locations. FIGURE 7 EFM remaining wall thickness map at the end of the experiment. FIGURE 8 Average detected metal loss by UT and EFM. Testing and Validation of Advanced Corrosion Monitoring Technology