Because each corrosion pattern behaves differently, every affected area must be evaluated individually, and a detailed inspection is required to characterize the corrosion mechanism and its extent before any repair strategy is developed. In most situations, isolated pitting does not significantly compromise the structural performance of the shell unless the pits are deep, clustered, or closely spaced.

The following sections outline the acceptance criteria for assessing both general metal loss and pitting in carbon-steel tank shells and provides example automated ultrasonic testing C-scan, phased array ultrasonic testing (PAUT) semi-encoded scans, and manual ultrasonic thickness testing results.

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