How to recognize steel tube failure？

Steel pipe corrosion is a diffusion-controlled process on exposed surfaces, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. In the steel and iron industry, most types of steel tube corrosion come with a continuous and virtually unstoppable process. Corrosion degrades the useful properties of steel pipes including strength, appearance and permeability to liquids and gases.

Most people commonly believe that many structural alloys corrode merely from exposure to moisture in air. Nevertheless, the corroding process starts in essence from the strong reaction with certain substances in environments. Here we would like to talk about a few common steel pipe failures in applications.

1. Uniform corrosion

Uniform corrosion or general corrosion, is defined as a type of corrosion attack (deterioration) that is more or less uniformly distributed over the entire exposed surface of cold rolled steel pipe. Uniform corrosion also refers to the corrosion that proceeds at approximately the same rate over the exposed metal surface. Specifically, cast irons and steels corrode uniformly when exposed to open atmospheres, soils and natural waters, leading to the rusty appearance.

2. Interior Pipe Deposits

For round steel pipe in applications, internal rust deposits, commonly termed tuberculation, are an inevitable death sentence for most piping systems. They are the lighter and less dense end product of steel tube corrosion. Once established by high and uncontrolled corrosion conditions, internal deposits initiate much greater deep pitting. The highest corrosion loss is more likely at horizontal lines and in low flow or dead end areas where rust and other deposits will settle, but can affect vertical lines and main risers as well. Random areas of high tuberculation are actually the result of a high pitting or cell corrosion condition directly beneath it, with the volume or height of the rust deposit directly proportionate to the depth and volume of pipe wall loss.

3. Weathering Damage

Generally speaking, weathering damage subject to rain, snow, atmospheric conditions, or cooling tower, overspray is the easiest to prevent. The piping is exposed and accessible, with corrosion activity always visually obvious. Most weathering damage requires decades to produce a failure, and is simply due to a lack of maintenance. Smaller diameter piping is always most vulnerable due to its inherently lesser wall thickness.

Of course, with regard to different types of pipe corrosion & failure in use, pipe repair work usually takes on various forms, ranging from temporary clamps to the replacement of entire piping systems. On the other hand, steel pipe manufacturers have various kinds of methods of surface treatment for steel tube done as precautions in a mill.