Scale and Corrosion: The Hidden Threats to High-Pressure Boilers

I.Boiler scale is primarily formed by the deposition of mineral ions present in the water, such as:
Calcium ions (Ca²⁺), magnesium ions (Mg²⁺), carbonates, sulfates, and silicates.

When raw water containing high levels of hardness ions enters the boiler, these substances gradually precipitate out under high-temperature and high-pressure conditions, adhering to the boiler tube walls and heat-exchange surfaces to eventually form a hard layer of scale.

2. What impact does scale have on high-pressure boilers?
(1) Reduced heat transfer efficiency
Scale has much lower thermal conductivity than metal. Even a scale layer just a few millimeters thick can lead to:
Increased fuel consumption
Decreased heating efficiency
Reduced steam output
(2) Increased equipment operating costs; scale leads to:
Frequent boiler blowdown
Shorter cleaning intervals
Higher maintenance costs
Reduced equipment service life
(3) Risk of localized overheating
When scale coats the boiler's heating surfaces, it impedes heat transfer, causing the temperature of the metal tube walls to rise abnormally.
In severe cases, this can result in:
Tube wall deformation
Cracking
Leaks
Boiler accidents

II.Boiler corrosion typically stems from the presence of the following in the water:

Dissolved oxygen (O₂), carbon dioxide (CO₂), chloride ions (Cl⁻), low-pH water, and impurities causing high conductivity; these substances continuously attack the boiler's metal surfaces.

2. Common Types of Boiler Corrosion
(1) Oxygen Corrosion
When dissolved oxygen enters the boiler system, it causes pitting corrosion,
which can easily lead to sudden leaks in boiler piping.

(2) Acid Corrosion
An increase in acidic substances in the water lowers the pH, accelerating metal corrosion.

Commonly found in:
Condensate systems
Feedwater systems
Chemical industry environments
Chloride Corrosion

III.To prevent issues with scale and corrosion, industrial boilers typically employ a comprehensive system combining pretreatment and pure water treatment.

Typical Process:

Raw Water → Multimedia Filter → Activated Carbon Filter → Water Softener → RO System → EDI / Mixed Bed → Boiler Feed Water

FAQ：

Q1: How can corrosion in boilers be reduced?

Corrosion can be controlled through proper water purification, oxygen removal, chemical dosing, and continuous water quality monitoring.

Q2: What is the best water treatment system for industrial boilers?

The ideal system depends on boiler pressure, raw water quality, and industry requirements. Common solutions include softeners, RO systems, and RO+EDI systems.

Q3:Future Trends of Boiler Water Treatment Systems

Future systems will focus more on the global trend of boiler water treatment moving towards intelligent systems:

Automatic monitoring and real-time detection:

TDS, pH, conductivity, flow rate, and automatic control

Achieved through PLC systems:

Automatic backwashing, automatic flushing, automatic alarm, automatic operation management, and water and energy conservation.