Zerust® Vapor Corrosion Inhibitors
Underground pipelines are required to have cathodic protection to protect them from corrosion. When these pipelines run under roadways, railway lines or other structures, they may also be required to have protective metal casings. Over time, movement can bring the pipeline and casing into contact, resulting in a metallic short that can cause the cathodic protection current to pass through the casing.
Vapor corrosion inhibiting gel can help mitigate this issue by protecting the space between the pipeline and casing. In addition, VCIs protect against corrosion caused by moisture, oxygen and other contaminants that may be trapped in this annular space.
When building a new pipeline, sections are typically hydrotested as they are completed. After hydrotesting, many owners will dry the section and purge the atmosphere with nitrogen. Often, these lines are not completely dry and the combination of water, oxygen and bacteria can have a negative corrosion effect on this new steel, even if the line has a nitrogen blanket. Maintaining the nitrogen can take time and be expensive, especially if the line will not be commissioned for a period of time.
Vapor corrosion inhibitors (VCI) have proven to be a cost-effective alternative to the traditional dry and N2 purge technique. In most cases, VCI can be introduced to both the non-piggable segments and the piggable lines very cost-effectively. The VCI can then preserve the line from corrosion for many years. When it is time to put the line into service, there are options for removing the small amounts of VCI slurry, or in some cases, simply start pumping the product. Similarly, existing lines can be preserved by VCIs after cleaning.
Soil side bottom (SSB) corrosion of aboveground storage tanks is a major cause of tank bottom failures. Such failures are often time-consuming and expensive to repair and may pose a potential hazard to the surrounding environment. The corrosion of tank bottom plates is often propagated by the ingress of external contaminants and moisture through gaps existing between the metallic plates and the underlying tank foundation.
Other factors influencing the propagation of corrosion to tank bottom plates include:
- Destruction of coating on the plates from welding or repairs
- Degradation of the underlying foundation over time
- Porous foundation types which can contain pre-existing gaps or void spaces