Corrosion Allowance (`corrosion`)

Corrosion Allowance

Calculate thickness and allowance for corrosion protection

Standards catalog

Validation: indicative · Method band: formula

Open calculator

Indicative method: Indicative closed-form or numerical model

Assumptions

Linear elastic material behavior unless noted otherwise.
User is responsible for load combinations and load factors per the selected design code.
Design standard (US/EU/ISO) sets unit defaults and screening check labels — not a full code worksheet.

Limitations

Professional screening / indicative workspace — does not replace a licensed PE or official code compliance review.
Where specialized evaluators are not implemented, checks map solver outputs to catalog templates for orientation only.

Engineering checks

Check	IND	US	EU	ISO
Remaining life margin	implemented	—	—	—
Required thickness margin	implemented	—	—	—

Purpose

Calculate required wall thickness including corrosion allowance and estimate remaining service life based on corrosion rate. Used for piping, vessels, and structural steel in corrosive environments.

Physics & theory

Corrosion progressively removes material from exposed surfaces at rate $r$ (mm/year typically). Design thickness must satisfy pressure/stress requirements at end of service life: $t_{design} = t_{min} + C A$ , where corrosion allowance $C A = r \cdot t_{life}$ .

Remaining life from inspection measurement: $t_{remaining} = (t_{measured} - t_{min}) / r$ . Allowable stress uses reduced thickness in hoop or general membrane formulas. Galvanic, pitting, and crevice corrosion require higher allowances than uniform general corrosion models.

Inspection thickness readings anchor remaining-life estimates; localized pitting may require a higher allowance than the uniform-rate model predicts.

Governing equations

C A = r \cdot t_{design_life}

t_{required} = t_{pressure} + C A

t_{remaining_life} = \frac{t _{now} - t _{min}}{r}

Numerical method

Closed-form allowance and life equations (engine). User supplies corrosion rate, design life, minimum structural thickness, and optional measured thickness for remaining life.

Inputs

Parameter	Description
`corrosionRate`	Material loss rate (mm/year)
`designLife`	Intended service years
`minThickness`	Structural/pressure minimum
`measuredThickness` (optional)	Current inspection reading
Environment class	Informative severity

Outputs

Corrosion allowance, required thickness, remaining life margin, thickness utilization.

Design codes & checks

Indicative: Remaining life margin, required thickness margin
US: ASME B31.3 corrosion allowance guidance
US: ASME VIII-1 UG-25 corrosion allowance

Assumptions & limitations

Uniform general corrosion; localized pitting not modeled.
Constant corrosion rate over life — no inhibition or passivation change.
Does not select CRA materials or coatings.
Inspection interval planning is user responsibility.

Verification

CI: corrosion-indicative-01.json
Engineer sign-off: validation-master-checklist.md

References

ASME B31.3:2022. Process Piping, corrosion allowance.
ASME BPVC Section VIII, Division 1, UG-25.
NACE SP0169. Control of External Corrosion on Underground Pipelines.
API 570. Piping Inspection Code.
Beer, F. P., et al. Mechanics of Materials, 8th ed. McGraw-Hill — foundational stress and deformation theory.

Maintainer note: Conservative allowance equations with straightforward inputs.

Corrosion Allowance

Assumptions

Limitations

Engineering checks

Corrosion Allowance (corrosion)

Corrosion Allowance (`corrosion`)