Short answer: A corrosion allowance is extra wall or section thickness added at design so a component still meets its minimum requirement after years of predictable metal loss; it is set from the service corrosion rate, design life and inspection plan.
At a Glance
What a Corrosion Allowance Does
The allowance absorbs uniform loss so the remaining section stays safe for the design life. It is the practical partner to How To Prevent Metal Rust y Metal Corrosion Inhibitor Guide, and it quantifies loss using Metal Corrosion Rate Calculation Guide y Metal Corrosion Testing Guide. Where loss is localised, see Pitting Corrosion Stainless Steel y Crevice Corrosion Stainless Steel.
Setting the Allowance
Allowance ≈ corrosion rate × design life + fabrication tolerance, with a margin for Metal Corrosion Under Insulation and unknown duty. Carbon steel in atmosphere might get 1-2 mm; buried or seawater pipe 2-3 mm; aggressive chemical 3-6 mm. Base rates on Mill Test Certificate Guide chemistry and real exposures from Seawater Corrosion Guide y Galvanic Corrosion Guide.
Materials, Inspection & QA
Where the rate is high, upgrade the alloy instead — Stainless Steel 316 Properties, Duplex Stainless Supplier o Copper Nickel Supplier — or add coating per Metal Surface Treatment Guide y Cathodic Protection Guide. Verify remaining thickness with Metal Ndt Guide and UT, and confirm the callout per Mill Test Certificate Guide.
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Preguntas frecuentes
Extra thickness added at design so a part still meets its minimum section after a calculated amount of uniform metal loss over its life.
Multiply the expected corrosion rate (mm/y) by the design life, add fabrication/forming tolerance and an inspection margin.
Typically 2-3 mm for carbon steel in soil, adjusted by coating, cathodic protection and the local corrosion rate.
When the rate is high or localised (pitting/crevice), upgrading to stainless, duplex or CuNi is usually cheaper than a very thick carbon-steel wall.
HXSCO supplies carbon, stainless, duplex and CuNi with documented chemistry and wall options to suit your allowance strategy.
Source Corrosion-Ready Metal from HXSCO
HXSCO supplies carbon, stainless, duplex and CuNi with documented chemistry and wall options for your corrosion-allowance design. Send your service, life and quantity for a quote.