Holiday Testing on Aged Coatings: Risky Business or Reliable Practice? (C2026-00190)

Amal Al-Borno, Henry Pedraza, Connor McManus, Julius Cortes

Field observations during the installation of fusion-bonded epoxy (FBE)-coated pipelines have revealed a recurring issue: while the initial holiday test identifies and allows for repair of coating defects, the final inspection during pipe lowering often detects significantly more discontinuities in aged coatings when compared to newly-applied coatings.
This study evaluates whether repeated holiday testing and adverse surface conditions contribute to the issue. Building on earlier work which showed that increased voltage (125–313 V/mil), slower travel speeds, UV aging, and contamination did not induce new holidays, additional protocols were introduced. Ten passes were conducted at 0.2, 0.5, and 1.0 ft/s on aged FBE panels with brine contamination, surface indentations, and reduced dry film thickness (DFT). New holidays were observed under these conditions, particularly at slower speeds and in areas of localized DFT reduction—even in the absence of salt contamination.
The study also explored the relationship between DFT and dielectric strength. While FBE can exhibit up to 1200 V/mil in lab conditions, field-applied voltages are lower. However, thin regions experience higher electric field intensity (E = V/d), increasing the risk of breakdown. Notably, applying 2000 V to 8-mil regions—below the theoretical limit—still caused failures, especially with salt present.