As explained throughout this article, the tanks included in this analysis provided an excellent format for side-by-side comparison of VCI and CP, where each technology is solely utilized to mitigate soil-side corrosion on new tank floors over a seven to 10-year time interval. The utilization of soil-side floor scan data generated during API 653 inspections produced an accurate data set from which to make the evaluations. The data produced the following interpretations: 1) VCI and CP corrosion indication data were statistically comparable for all five VCI tanks with four of the CP-only tanks (numbers 4, 5,6,12). 2) All five VCI-only tanks performed significantly better when compared to the CP-only tanks numbers 7,8,10. 3) The reasons for the large disparity in the three CP-only tanks (numbers 7, 8, 10) are not understood at this time. There were no operational issues with the CP systems. No information was recorded during the inspection of these tanks to explain the significantly higher number of indications. Speculation on the reasons for these outliers is not included in the scope of this article. 4) Within this sample group, it is important to note that the differ- ences in the number of corrosion indications for the five VCI-only tanks were not large. a) The total number of indications for the five VCI-only tanks ranged from 1 to 20; and the average corrosion rates of the indications ranged from 165.1 to 327.7 μm/y (6.5 to 12.9 mpy). b) Whereas, the total number of indications for the seven CP-only tanks ranged from 6 to 154; and the corrosion rates of these indications ranged from 165.1 to 500.4 μm/y (6.5 to 19.7 mpy).
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