---
title: "Cold-end corrosion / dew-point corrosion"
description: "Cold-end corrosion (also dew-point corrosion) is the attack on boiler air-heater baskets, economiser tubes and downstream ducting where flue-gas temperature falls below the acid dew point of the gas. SO₃ in the flue gas combines with water vapour to form sulphuric acid that condenses on the cooled surfaces and attacks them."
canonical_url: "https://sylio.co/glossary/cold-end-corrosion-dew-point-corrosion"
last_updated: "2026-06-28T02:29:25.926Z"
---

**Cold-end corrosion** (also *dew-point corrosion*) is the attack on boiler [air-heater](/glossary/air-heater) baskets, [economiser](/glossary/economiser) tubes and downstream ducting where flue-gas temperature falls below the [acid dew point](/glossary/acid-dew-point) of the gas. SO₃ in the flue gas combines with water vapour to form sulphuric acid that condenses on the cooled surfaces and attacks them.

## The interplay with fouling

Cold-end corrosion and fouling reinforce each other:

- Condensed acid bonds dust to surfaces — fouling consolidates faster
- Fouled tubes run cooler than design — more acid condenses
- [Ammonium bisulphate (ABS)](/glossary/ammonium-bisulphate) deposits accelerate both processes

The result is a self-feeding cycle: a unit that begins to foul typically also begins to corrode, and both worsen until the cold end is water-washed or rebuilt.

## Mitigation

- Maintain cold-end metal temperature above the [acid dew point](/glossary/acid-dew-point)
- Manage fuel sulphur and SCR SO₂/SO₃ conversion
- Use corrosion-resistant materials (Cor-Ten, enamel-coated baskets) at the cold end
- Periodic water-washing of cold-end baskets and tubes
- [Sonic horns](/glossary/sonic-horn) to keep deposits from consolidating

## Related terms

- [Air heater](/glossary/air-heater)
- [Economiser](/glossary/economiser)
- [Ammonium bisulphate](/glossary/ammonium-bisulphate)
- [Acid dew point](/glossary/acid-dew-point)
- [Boiler tube failure](/glossary/boiler-tube-failure)