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Pitting of Copper in Heat Exchanger System

EQUIPMENT: Heat Exchanger

ENVIRONMENT:

Water

MATERIAL:

Copper

SERVICE TIME:

Unknown

FAILURE:

Pitting Attack

 

Copper tubing with aluminum fins was employed in a heat exchanger system. Temperature was controlled by circulating water through the copper tubes. Pin hole leaks were observed in the copper tubing at the time of failure.

Cutting the tubes in half longitudinally revealed extensive corrosive attack, primarily pitting on the inside diameter (Figure 1).

SEM (scanning electron microscope) equipped with EDS (energy dispersive x-ray spectroscopy) was used to identify the elemental components of the various corrosion products observed. A high level of chlorine along with lower levels of sulfur and iron were detected.

Corrosive attack was due to a high level of chloride and sulfur compound most likely present in the water. The presence of iron indicates contamination due to corrosion occurring elsewhere in the system.

 
Figure 1. Corrosion products and pitting on ID of copper tubing (11X Original Magnification)

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