Since entering the 21st century, China's economy has maintained strong and sustained growth, and the demand for various types of gas and oil has gradually increased. Moreover, compared with transportation by vehicles and ships, pipeline transportation has the advantages of high efficiency, economy, safety and continuity, making it the preferred method for long-distance transportation.
To ensure the economy and safety of pipeline construction and operation, the basic requirements and development trends of pipeline steel are high strength, high toughness, large deformability, thick wall, high corrosion resistance and good welding performance. The pre-fine welding technology is currently an advanced technology in the production of large-diameter and thick-walled pipelines. However, due to constraints such as operation and welding processes, rust spots will appear at the welds after applying anti-corrosion coatings, which affects the weld quality and thus reduces the pipeline quality.
When applying water-based coatings on pipeline welds, if natural drying is used to form a film, water will stay on the metal substrate for a long time, leading to rapid rusting at the welds. This phenomenon is called "flash rust".
Flash rust is an electrochemical phenomenon, and its occurrence is related to the dissolution and precipitation of iron compounds. Since water-based coatings themselves are conductors, they form charge migration channels for different areas with potential differences, resulting in corrosion under the combined action of water and oxygen.