Corrosion is one of the important elements that cause valve damage. In valve protection, valve anti-corrosion is an important issue to be considered. For metal valves, surface coating treatment is the best cost-effective protection method.
1、 Effect of surface coating
1. Shielding effect
After the metal surface is coated with paint, the metal surface is relatively separated from the environment. This protective effect can be called shielding effect. However, it must be pointed out that a thin coating cannot play an absolute shielding role. Because polymers have a certain permeability, when the coating is very thin, its structural pores can allow water and oxygen molecules to pass freely. Frexi soft seal 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 that of the steel surface without coating. In order to improve the impermeability of the coating, the anticorrosive coating shall be made of film-forming materials with low permeability and solid fillers with high shielding. At the same time, the number of coating layers shall be increased to make the coating reach a certain thickness and dense without holes.
2. Corrosion inhibition
With the help of the reaction between the internal components of the coating and the metal, the metal surface is passivated or protective substances are generated to improve the protective effect of the coating. For valves with special requirements, pay attention to the paint composition to avoid serious adverse effects. In addition, the cast steel valves used in oil pipelines can also act as organic corrosion inhibitors due to the degradation products generated under the action of some oils and the drying action of metal soaps.
3. Electrochemical protection
When the dielectric penetration coating contacts the metal surface, it will form electrochemical corrosion under the film. Metals with higher activity than iron are used as fillers in coatings, such as zinc. It will protect the sacrificial anode, and the corrosion products of zinc are basic zinc chloride and zinc carbonate, which will fill the gap of the film and make the film tight, thus greatly reducing the corrosion and extending the service life of the valve.
2、 Coating used for Fraser valves
1. Epoxy resin coating of valve body
It has the following characteristics:
Corrosion resistance
Epoxy resin coated steel bars have good corrosion resistance, and the bond strength with concrete is obviously reduced, which is suitable for the wet environment or corrosive medium.
Strong adhesion
The existence of polar hydroxyl and ether bond inherent in the epoxy resin chain makes it have a very good adhesion to various substances. The epoxy resin has low shrinkage when curing, and the inner part of the epoxy resin should be smooth, so that the surface coating is not easy to fall off.
Electrical performance
The cured epoxy resin system is a kind of excellent insulating material with dielectric property, resistance to surface leakage and arc resistance.
Mould resistant
The cured epoxy resin system is resistant to most molds and can be used under harsh tropical conditions.
2. Valve plate nylon plate material
Nylon 11 has extremely strong corrosion resistance, which has successfully made it used in many application fields, such as water, mud, water and sea water desalination.
Outdoor sex
Frexi's Nixi 11 coating can pass the salt spray expansion test at 2000 ℃, and the coating has not peeled off after being immersed in the sea for more than 25 years, so there is no corrosion to the parts.
Abrasion resistance
It has good resistance to damage.
Impact resistance
Under strong impact, there is evidence of peeling off.
3. Carbon steel valve plate zero treatment
Provide protection for the base metal to prevent corrosion of the metal to a certain extent; It is used for priming before painting to improve the adhesion and corrosion resistance of paint film; The antifriction lubrication is used as lubricating oil in the cold heating process.
