What are pinholes, and how do they form?
Pinholes are tiny holes that can appear in the coating or weld seam of a pipeline. In coatings, pinholes often look like small raised spots or broken blisters on the surface. They are usually caused by contamination on the pipe prior to coating, such as soluble salts or corrosion products that trap moisture. When the pipe is heated during the coating process, this moisture turns to vapor and forms bubbles that appear as pinholes. In welding, a pinhole refers to a short, unwelded area in the bond line that can extend through the pipe wall. This creates a very slow leakage path for liquids, allowing them to escape slowly. Thin-walled pipes are more prone to this issue.1
What are the risks of pinholes?
Although pinholes may seem small, they can lead to serious problems, such as leaks. Weld-related pinholes cause slow leakage paths that can compromise the integrity of the pipeline over time.1
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Source reference
The Encyclopedia of Pipeline Defects, ROSEN UK, Edition 3, 2017.