Understanding Copper Pipe Failures: A Technical Insight into Corrosion and Reliability

When industries rely on copper piping for fluid circulation, system reliability depends on more than just material strength—it hinges on long-term resistance to corrosion. At CMH Met Labs, we recently conducted a detailed failure analysis on copper pipe samples of one of our client, uncovering the root causes behind premature failures in service.

Section of the one of the pipes that shows a round dark abnormality at the interior pointed to by the arrow.

This case study provides a clear example of how advanced metallurgical techniques can identify hidden risks and guide corrective measures.

Why Failure Analysis Matters

Unexpected equipment failure can lead to costly downtime, safety hazards, and reduced efficiency. Failure analysis goes beyond surface observations—it answers the “why” behind material breakdowns. By combining optical microscopy, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS), we can pinpoint failure mechanisms and recommend solutions that prevent recurrence.

Step 1: Visual and Microscopic Examination

The copper pipe samples first underwent visual inspection and stereomicroscopy. Although no through-thickness cracks were visible, discoloration and abnormal surface features were noted inside the pipes.

After careful sectioning, mounting, grinding, and polishing, cross-sectional and longitudinal samples were examined under an optical microscope. Images revealed:

  • Interior surface corrosion: Degradation consistently originated from the inner pipe walls.
  • Progressive damage: Corrosion extended deep into the pipe wall thickness, threatening pressure resistance over time.
  • Hidden defects: In some cases, corrosion “pockets” were found in the middle of the pipe wall, not visibly connected to the inner surface—making them invisible to the naked eye.

Step 2: Micro-Structural Insights

Polished and etched specimens revealed the grain structure of the copper alloy. In many materials, corrosion follows preferred grain boundaries. However, due to the fine grain size and the extent of damage, corrosion spread more uniformly across the structure.

Images of the etched samples taken from the pipe marked as #2 in longitudinal direction, showing grain microstructure in the copper pipe. (a) and (b), are at 200x and 400x, respectively.

This confirmed that the material itself was sound but became compromised under specific service conditions.

Step 3: Advanced SEM & EDS Analysis

To better understand the corrosion mechanism, we used SEM coupled with EDS to analyze affected areas. The results were consistent:

  • Copper and oxygen dominated the corrosion products.
  • Traces of nickel (≈1%) were occasionally detected, but not significant enough to be the root cause.
  • No evidence of foreign contaminants like sulfur or chlorine was found in the corrosion zones.

These findings pointed to oxidizing agents in the circulating liquid as the driving factor behind the corrosion process.

Key Findings

  1. Progressive internal corrosion weakened the copper pipe walls from within.
  2. Oxidizing agents in the circulating liquid initiated and sustained corrosion.
  3. Pressure and temperature fluctuations may have accelerated failure, especially if wet/dry cycles occurred.
  4. Wall thickness was insufficient to withstand long-term service under these conditions.

Recommendations for Industry

Based on the findings, our materials engineers provided the following corrective measures:

    • Fluid chemistry control: Ensure circulating liquids are free from oxidizing agents.
    • Monitoring programs: Implement regular checks on pH, oxygen content, and corrosion inhibitors in fluid systems.
    • System operation: Avoid frequent on/off cycles that encourage wet/dry corrosion cycles.
    • Design improvements: Where possible, use thicker-walled copper pipes to extend service life.

Why Choose CMH Met Labs?

At CMH Met Labs, we don’t just test materials—we deliver actionable insights that help clients reduce costs, improve safety, and enhance reliability. Our team combines metallurgical expertise with advanced equipment to solve real-world problems in metals, polymers, composites, and coatings.

If you’re facing unexplained material failures, our ISO 17025-accredited lab provides:

  • Chemical composition analysis (OES, EDS, FTIR, DSC/TGA)
  • Mechanical and micro-structural testing (tensile, hardness, metallography)
  • Failure investigations tailored to your industry

Copper pipe failures in this case were caused not by defective material, but by corrosive service conditions. By controlling system chemistry and design factors, industries can prevent similar failures and improve long-term reliability.