5. Spray paint
Coating is a widely used anti-corrosion method, and it is an indispensable anti-corrosion material and identification mark on valve products. Paint is also a non-metallic material. It is usually made of synthetic resin, rubber slurry, vegetable oil, solvent, etc., covering the metal surface, isolating the medium and the atmosphere, and achieving the purpose of anti-corrosion. Coatings are mainly used in environments that are not very corrosive, such as water, salt water, sea water, and the atmosphere. The inner cavity of the valve is often painted with anti-corrosion paint to prevent water, air and other media from corroding the valve. The paint is mixed with different colors to indicate the materials used in the valve. The valve is sprayed with paint, usually every six months to a year.
6. Add corrosion inhibitor
The mechanism of the corrosion inhibitor to control corrosion is that it promotes the polarization of the battery. Corrosion inhibitors are mainly used for media and fillers. Adding corrosion inhibitors to the medium can slow down the corrosion of equipment and valves. For example, chromium-nickel stainless steel will become cremated in a large solubility range in oxygen-free sulfuric acid, and the corrosion will be more serious. Add a small amount of copper sulfate or nitric acid, etc. The oxidizer can make the stainless steel passivate, and a protective film is formed on the surface to prevent the corrosion of the medium. In the hydrochloric acid, if a small amount of oxidant is added, the corrosion of titanium can be reduced. Water is often used as the pressure test medium for valve pressure testing, which is easy to cause corrosion of the valve []. Adding a small amount of sodium nitrite in the water can prevent water from corroding the valve [].
7. Electrochemical protection
Electrochemical protection has two types: anode protection and cathodic protection. If zinc is used to protect iron and zinc is corroded, zinc is called sacrificial metal. In production practice, anode protection is used less and cathodic protection is used more. Large valves and important valves adopt this cathodic protection method, which is an economical, simple and effective method. Zinc is added to asbestos filler to protect the valve. Rods are also cathodic protection laws.
8. Control the corrosive environment
The so-called environment, there are two kinds of broad sense and narrow sense. The broad sense refers to the environment around the valve installation place and its internal circulation medium; the narrow sense refers to the conditions around the valve installation place. Most environments cannot be controlled, and production processes cannot be changed arbitrarily. Only in the case of no damage to products, processes, etc. can be used to control the environment, such as boiler water deoxygenation, increase or decrease the PH value of the oil refining process, etc. The atmosphere is full of dust, water vapor, and smoke. Especially in the production environment, such as smoke bittern, toxic gases and micro-powder emitted from equipment, will cause different degrees of corrosion to the valve. The operator should clean and purge the valve regularly and refuel regularly according to the regulations in the operating regulations. This is an effective measure to control environmental corrosion. The valve stem is installed with a protective cover, the ground valve is installed with a well, and the valve surface is sprayed with paint. These are all methods to prevent corrosive substances from corroding the valve. Elevated environmental temperature and air pollution, especially for equipment and valves in a closed environment, will accelerate its corrosion. Open workshops or ventilation and cooling measures should be adopted as much as possible to slow down environmental corrosion.
9. Improve processing technology and valve structure
The anti-corrosion protection of the valve is a problem that is considered from the beginning of the design. A valve product with a reasonable structure design and correct process method will undoubtedly have a good effect on reducing the corrosion of the valve. Therefore, the design and manufacturing department should make improvements to those parts with unreasonable structural design, incorrect process methods, and easy to cause corrosion to make them suitable for the requirements of various working conditions.
