Direct Current Voltage Gradient Survey (DCVG Survey)
Definition - What does Direct Current Voltage Gradient Survey (DCVG Survey) mean?
A direct current voltage gradient (DCVG) survey is a type of survey method that is used to assess the efficacy of corrosion protection, particularly on structures buried underground.
This is highly useful in the natural gas and oil industries, as this technique is used to trace coating faults as well as determine the deficits in the strategies that are used to control corrosion.
Corrosionpedia explains Direct Current Voltage Gradient Survey (DCVG Survey)
Steels that are buried go through corrosion over time if not given the proper protection against corrosion. The rate of corrosion is faster in soils that are subjected to corrosive elements like saltwater. The first line of corrosion protection includes the application of protective coatings like resin and epoxy. These are usually enhanced with cathodic protection. As the pipes get old, the coating undergoes deterioration, and this is where the appropriate cathodic protection becomes essential in preventing the damage that corrosion brings.
Before the utilization of DCVG, it is vital to assess the overall condition of the coatings. DCVG was originally developed to find faults in coating, determine the severity of damage as well as gauge the effectiveness of the cathodic protection in use without the need to agitate the pipeline.
A DCVG survey is considered the most reliable method to measure and trace coating defects in pipelines. It is based on quantifying voltage gradients present in the soil over pipelines that are under cathodic protection.