Corrosion of metal needle valve

Corrosion of a needle valve is typically defined as the degradation of its metallic components due to exposure to a chemical or electrochemical environment. This process occurs naturally when metal comes into contact with its surroundings, making it essential to either isolate the metal from the environment or use non-metallic synthetic materials as a preventive measure.

The body of a needle valve, including the valve cover, constitutes the majority of the valve’s weight and is frequently exposed to the working medium. Therefore, material selection for the body is a key consideration in valve design and application.

Corrosion of the valve body can occur in two primary forms: chemical corrosion and electrochemical corrosion. The rate at which corrosion happens depends on several factors, such as temperature, pressure, the chemical properties of the medium, and the corrosion resistance of the material used. Based on this rate, corrosion resistance can be categorized into six levels:

  • 1. Excellent corrosion resistance: less than 0.001 mm per year;
  • 2. Very high corrosion resistance: 0.001 to 0.01 mm per year;
  • 3. High corrosion resistance: 0.01 to 0.1 mm per year;
  • 4. Moderate corrosion resistance: 0.1 to 1.0 mm per year;
  • 5. Low corrosion resistance: 1.0 to 10 mm per year;
  • 6. No corrosion resistance: more than 10 mm per year.

Understanding these categories helps engineers and technicians choose the most suitable materials for specific applications, ensuring the longevity and reliability of needle valves in various environments.

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