Corrosion Rate & Remaining Life Calculator

Free Engineering Tool

Three standard methods used in asset integrity and corrosion monitoring work: mass loss (per ASTM G1), thickness loss from inspection data, and remaining life estimation against a minimum allowable thickness. For general, uniform corrosion screening, not a substitute for facility inspection codes such as API 570 or API 580.

Mass Loss Method

Based on ASTM G1: CR = (K × W) / (A × T × D), where W is mass loss, A is exposed surface area, T is exposure time, and D is metal density.

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Exposed area (A)

Exposure time (T)

Metal density (D)

Corrosion Rate

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Note: assumes uniform corrosion over the full exposure period on a representative coupon or component. Does not capture localized attack such as pitting, crevice corrosion, or microbially influenced corrosion. K constants per ASTM G1-03 (mpy: 3.45×10&sup6;, mm/yr: 8.76×10&sup4;, µm/yr: 8.76×10&sup7;, ipy: 3.45×10³).

Thickness Loss Method

Derives corrosion rate directly from two thickness measurements (e.g. UT readings) taken at different times. CR = (initial thickness − final thickness) / elapsed time.

Initial thickness

Current / final thickness

Elapsed time

Corrosion Rate

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Note: reflects average corrosion rate between the two inspection points only. Where possible, use trend data from three or more inspection intervals rather than a single two-point reading, since localized thinning or measurement error in a single UT reading can distort a two-point rate.

Remaining Life Estimator

Estimates remaining service life from current measured thickness, minimum allowable (retirement) thickness, and a known or assumed corrosion rate.

Current thickness

Minimum allowable thickness (t-min)

Corrosion rate

Estimated Remaining Life

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Note: minimum allowable thickness should come from a code-based calculation (e.g. ASME B31.3, API 510/570) for the specific component, not assumed. Recommended next inspection interval shown here follows the common risk-based inspection rule of thumb of half the remaining life, capped per applicable code or company policy; always confirm against your facility's RBI programme and inspection code requirements.

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