In industrial water systems, people often use “corrosion” and “erosion” interchangeably—but they’re very different problems with different root causes and different solutions. Misdiagnosing one for the other can lead to wasted money and persistent equipment damage.
Corrosion: A Chemical or Electrochemical Reaction
Corrosion happens when water chemistry interacts with metal surfaces. Low pH, dissolved oxygen, high chlorides, or oxidizing biocides can all attack system metals. Corrosion often appears as:
• pitting
• uniform thinning
• tuberculation (in iron systems)
• rust or oxide films
The fix? Adjust water chemistry, maintain inhibitors, eliminate oxygen, and manage biocide levels.
Erosion: A Mechanical Wear Process
Erosion, on the other hand, comes from velocity, turbulence, or suspended solids wearing away metal surfaces. It shows up as smooth, shiny, horseshoe-shaped patterns rather than pits or rust. Causes include:
• high-velocity elbows
• improperly sized pumps
• sand or grit in the water
• cavitation
Preventing erosion requires reducing velocity, improving filtration, correcting pump design, or adding wear-resistant linings—not adding corrosion inhibitor.
The Worst Case: Erosion-Corrosion
Sometimes both mechanisms occur at once. High-velocity water strips protective films from metal surfaces, exposing them to rapid chemical attack. This makes the metal fail much faster than either mechanism alone.
Expert Treatment for All Water Issues
Corrosion is chemical. Erosion is mechanical. For accurate diagnosis, facilities should combine metallurgical inspection, water chemistry review, and flow modeling. Getting it right ensures you apply the right fix and avoid costly guesswork.