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. Since corrosion occurs naturally when metal interacts with its surroundings, the primary goal of corrosion prevention is to either isolate the metal from the environment or replace it with more durable non-metallic materials.

The body of a needle valve, including the valve cover, makes up the majority of the valve’s weight and is in constant contact with the process medium. Therefore, material selection for the body is a critical factor in determining the valve’s overall performance and longevity.

Corrosion of the valve body can occur in two main forms: chemical corrosion and electrochemical corrosion. The rate at which this occurs depends on several factors, such as temperature, pressure, the chemical properties of the medium, and the corrosion resistance of the valve material itself. Corrosion rates are often categorized into six levels:

• 1. Excellent corrosion resistance: less than 0.001 mm/year
• 2. Very high corrosion resistance: 0.001–0.01 mm/year
• 3. Good corrosion resistance: 0.01–0.1 mm/year
• 4. Moderate corrosion resistance: 0.1–1.0 mm/year
• 5. Poor corrosion resistance: 1.0–10 mm/year
• 6. No corrosion resistance: over 10 mm/year

Understanding these classifications helps engineers and technicians choose the most suitable materials for specific applications, ensuring long-term reliability and safety in industrial environments.