Boiler Corrosion Prevention: Causes and Simple Measures

Oct. 1, 2026

Introduction

In our previous column, we explained how to prevent scale in boilers. This time, we would like to look at another important problem caused by water quality: corrosion. In this column, we will explain the main causes of corrosion and the basic points of boiler corrosion prevention.

What Is Corrosion?

Corrosion is the gradual damage of metal caused by chemical reactions with water and gases. Inside a boiler, corrosion slowly makes the metal thinner and weaker.

Unlike scale, corrosion often progresses without clear signs. When a leak or damage is found, the problem may already be serious.

Main Causes of Corrosion in Boilers

Dissolved oxygen
Oxygen in the feed water reacts with the metal. It can cause small, deep holes called “pitting.”
Low pH (acidic water)
If the pH of the boiler water drops below the proper range, the metal surface is attacked more easily. Carbon dioxide in the water can lower the pH.
Long shutdown periods
When a boiler is stopped for a long time, air and moisture remain inside. This can cause corrosion even while the boiler is not in use.

Signs You Should Not Ignore

Reddish or brown water during blowdown
Small leaks or wet areas around the boiler
Frequent trouble in piping or valves

If you notice any of these signs, we recommend checking your boiler water condition as soon as possible.

Three Basic Steps for Boiler Corrosion Prevention

Reduce oxygen in the feed water
Use deaeration equipment or chemicals that remove oxygen.
Keep the boiler water within the correct pH range
Boiler water should be kept at the alkaline level recommended by the manufacturer. Check the water quality regularly.
Protect the boiler during shutdown
Before a long stop, follow the proper storage method for your boiler.

What We Will Share Next

In our columns on scale and corrosion, we mentioned blowdown several times. In our next column, we will explain what blowdown is and how to do it properly.