Corrosion is one of the important elements that cause butterfly valve damage. In butterfly valve protection, butterfly valve corrosion protection is an important issue to consider. For metal butterfly valves, surface coating treatment is the best cost-effective protection method.
The role of metal butterfly valve surface coating
01. Shielding
After the metal surface is coated with paint, the metal surface is relatively isolated from the environment. This protective effect can be called shielding effect. But it must be pointed out that a thin layer of paint cannot play an absolute shielding role. Because the high polymer has a certain air permeability, when the coating is very thin, its structural pores allow the molecules of water and oxygen to pass freely. Soft-sealed butterfly valves have strict requirements on the thickness of the epoxy coating on the surface. It can be seen that for many coatings the value is greater than the uncoated steel surface. In order to improve the impermeability of the coating, the anti-corrosion coating should use a film-forming substance with low air permeability and a solid filler with a large shielding property, and at the same time, the number of coating layers should be increased so that the coating can reach a certain thickness and be dense and non-porous.
02. Corrosion inhibition
By reacting the internal components of the coating with the metal, the metal surface is passivated or a protective substance is generated to improve the protective effect of the coating. butterfly valves used for special requirements must pay attention to the composition of the paint to avoid serious adverse effects. In addition, the cast steel butterfly valve used in the oil pipeline, the degradation products generated under the action of some oils and the drying action of metal soaps can also play the role of organic corrosion inhibitors.
03. Electrochemical protection
Electrochemical corrosion under the film occurs when the dielectric permeable coating comes into contact with the metal surface. Use metals with higher activity than iron as fillers in coatings, such as zinc. It will play the protective role of sacrificial anode, and the corrosion products of zinc are basic zinc chloride and zinc carbonate, which will fill the gap of the membrane and make the membrane tight, which greatly reduces the corrosion and prolongs the service life of the butterfly valve.
Commonly used coatings for metal butterfly valves
01. butterfly valve body epoxy resin coating
Has the following characteristics:
Corrosion resistance
Epoxy-coated steel bars have good corrosion resistance, and the bond strength with concrete is significantly reduced. It is suitable for industrial conditions in humid environments or aggressive media.
strong adhesion
The presence of polar hydroxyl and ether bonds inherent in the molecular chain of epoxy resins makes it highly adhesive to various substances. Epoxy resin has low shrinkage during curing, and the internal stress generated is small, and the protective surface coating is not easy to fall off and fail.
Electrical properties
The cured epoxy resin system is an excellent insulating material with high dielectric properties, surface leakage resistance and arc resistance.
Mold resistant
Cured epoxy systems are resistant to most molds and can be used in harsh tropical conditions.
02. butterfly valve plate nylon plate material
Nylon sheets are extremely corrosion-resistant and have been successfully used in many applications such as water, mud, food, and desalination.
outdoor sex
The nylon board coating can pass the salt spray test, and the coating has not peeled off after being immersed in sea water for more than 25 years, so there is no corrosion to metal parts.
abrasion resistance
Has very good damage resistance.
impact resistance
There is no sign of peeling under strong impact.
Post time: Nov-24-2022