Petroleum, Natural Gas And Oilfield Protection
Cathodic protection is a technology that prevents metal corrosion through electrochemical principles and is widely used in metal facilities such as pipelines, storage tanks and deranges in the oil and gas industry. The core principle is: through external current or sacrificial anode, the protected metal structure becomes the cathode of the electrochemical cell, suppressing the oxidation reaction (corrosion) on the metal surface, thereby extending the service life of the equipment.
The commonly used cathodic protection in petroleum, natural gas and oil fields is divided into two types: sacrificial anode cathodic protection and impressed current cathodic protection.
Sacrificial anode cathodic protection：
- Principle: A metal with a more negative potential (such as zinc, aluminum, and magnesium alloys) is used as the anode and connected to the metal to be protected. Through its own corrosion, it provides a protective current for the metal structure.
- Features:
- It does not require an external power supply and is suitable for remote or power-free areas (such as single-well pipelines and small storage tanks).
- It is easy to install and has low maintenance costs, but the anode needs to be replaced regularly after consumption.
Impressed current cathodic protection：
- Principle: Through an external power source such as a transformer rectifier, a cathodic current is applied to the protected metal to counteract the corrosion current. The system includes auxiliary anodes (such as high-silicon cast iron, graphite), reference electrodes (for monitoring potential), and power supply equipment.
- Features:
- It has a wide protection range and adjustable current output, making it suitable for complex scenarios such as long-distance pipelines and large tank groups.
- A stable power supply (either mains electricity or solar power) is required. The initial investment is relatively high, but the long-term cost is controllable.
- Composition:
- Transformer rectifier
The transformer rectifier precisely controls the output current and voltage to provide a stable cathodic polarization current for the protected metal, keeping its potential within a corrosion-resistant and safe range.
2. Anode ground bed:
The function of the auxiliary anode is to transfer the direct current output by the direct current power supply from the medium to the protected metal structure.
3. Reference electrode:
- Reference electrode for measurement: Monitors the potential of the protected structure.
- Control reference electrode: It provides control signals for the automatically controlled transformer rectifier to adjust the output current, ensuring that the protected structure is always in a good protective state.
4. Monitoring System:
Real-time transmission of potential and current data to warn of abnormal corrosion risks.