A Problem with Pipes - Leaks & Corrosion
What Happened?
I was contacted by a mechanical services company who had installed a commercial boiler system some years ago. They had been recently notified by their client that a leak had formed within an elbow section of the pipe work, which required replacement. The leaky section was examined by the installers, and the internal surface of the pipe was seen to be severely corroded.
The mechanical services contacted me, and explained the issue. The section of pipe was delivered to my Dublin-based laboratory. I was asked to examination the pipe, the leak that had formed, and the corrosion processes which had led to it.
“This high concentration of chlorine found in the water showed the third party had failed in their duties, and were responsible for the necessary repairs. ”
How did we analyse it?
First of all, the pipe had to be cut in half along its length to examine the internal surface in better detail. The whole internal surface was coated with corrosion products (rust), with many wide, deep pits and valleys gouged into the pipe wall. In one location, the pipe wall thickness had been ruptured, creating a hole measuring approximately 0.7 mm. I used a suite of optical and digital microscopy equipment to examine the markings on the internal wall in closer detail.
A directional pattern was observed in these marks, proceeding in the path of flow of the steam carried by the pipe, as indicated by the red arrows. This directional pattern is characteristic of erosion corrosion, a process by which standard corrosion is enabled or accelerated by the passage of high-velocity fluids, which impact the metal surface. These impacts can break down or prevent the formation of protective coatings on the metal surface. As manufactured, this pipe had received a protective lacquer coating, which had evidently been damaged by the passage of steam through the pipe.
I collected some of the corrosion product material from within these pits and valleys to examine with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), which detected the presence of chlorine. Chlorine is known to cause and accelerate corrosion of steel, and would have contributed significantly to the formation of the leaks. This chlorine most likely originated from the water used within the boiler system.
What was the resolution?
On my recommendation, the company tested the water used in the boiler system. A high concentration of chlorine was found, which undoubtedly contributed to the formation of the leaks in the pipe system. A third-party company had been hired to monitor, test, and control the quality of the water being used in the steam boiler system. This high concentration of chlorine found in the water showed the third party had failed in their duties, and were responsible for the necessary repairs.
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