Corrosion Rate
Corrosion rate is the rate of wall-thickness loss in mm/year (or mils/year) calculated from successive thickness measurements, used to determine remaining life and inspection intervals under API inspection codes.
Definition
Short-term corrosion rate uses the two most recent measurements; long-term rate uses original thickness minus current thickness divided by service years. The higher of the two values is conservatively used for remaining-life calculation.
Related terms
- Remaining Life — Remaining life is the calculated time until equipment reaches its retirement thickness or minimum required thickness at the current measured corrosion rate, used by API 510/570/653 to set the next inspection interval.
- Minimum Required Thickness — Minimum required thickness is the wall thickness required to safely contain design pressure plus any required corrosion allowance, calculated per ASME Section VIII or B31.3 equations and used as the design-basis comparison for thickness measurements.
- T-min (Minimum Thickness) — T-min is the minimum acceptable in-service wall thickness, equal to the larger of the pressure-design minimum and the structural-stability minimum, used as the threshold below which equipment must be repaired or retired.
Further reading
ultrasonic thickness measurement corrosion monitoring guide
More data terms
A-Scan · B-Scan · C-Scan · D-Scan · S-Scan · L-Scan · Distance-Amplitude Correction · Distance-Gain-Size · Time-Corrected Gain · Gating
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.