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How to choose the valve of different material

Posted by Bundor valve
Many media are somewhat corrosive;The corrosivity of the same medium varies with pressure, temperature and concentration.Therefore, according to the corrosion resistance of the material, the choice of suitable for the medium of the valve.
1. Stainless steel valve
Stainless steel valves have good gas resistance, can withstand nitric acid and other oxidizing media, can also withstand alkali, water, salt, organic acids and other organic compounds corrosion.But not resistant to sulfuric acid, hydrochloric acid and other non-oxidizing acid corrosion, also not resistant to dry hydrogen chloride, oxidizing chloride and organic acids such as oxalic acid, lactic acid.Stainless steel containing molybdenum 2% ~ 4%, such as Cr18Ni12Mo2Ti, its corrosion resistance is better than chromium nickel stainless steel, it in non-oxidizing acid and hot organic acid, chloride acid resistance is better than chromium nickel stainless steel, corrosion resistance is also good.Stainless steel containing titanium or niobium has strong resistance to intergranular corrosion.Containing high chromium, high nickel stainless steel, its corrosion resistance performance is higher than ordinary stainless steel, can be used to deal with sulfuric acid, sulfuric acid, mixed acid, sulfurous acid, organic acid, alkali, salt solution, hydrogen sulfide, and even can be used in some concentrations of high temperature occasions.But it is not resistant to the corrosion of concentrated or hot hydrochloric acid, wet fluorine, chlorine, bromine, iodine and aqua royal.
2. Cast iron valve
Suitable for water, steam, petroleum products, ammonia can work in the majority of alcohol, aldehydes, ether, ketone, grease and other less corrosive medium.It is not suitable for hydrochloric acid, nitric acid and other media.But it can be used in concentrated sulfuric acid because concentrated sulfuric acid can produce a passivating film on its metal surface.To prevent concentrated sulfuric acid corrosion of cast iron.
Gray cast iron valve
Suitable for water, steam, petroleum products, ammonia can work in the majority of alcohol, aldehydes, ether, ketone, grease and other less corrosive medium.It is not suitable for hydrochloric acid, nitric acid and other media.But it can be used in concentrated sulfuric acid because concentrated sulfuric acid can produce a passivating film on its metal surface.To prevent concentrated sulfuric acid corrosion of cast iron.
Ductile iron valve
Corrosion resistance is strong, can work in a certain concentration of sulfuric acid, nitric acid, sulfuric acid, acid salt.However, it is not resistant to the corrosion of hot solution of fluoric acid, strong base, hydrochloric acid and ferric chloride.Use to avoid sudden heat, sudden cold, or it will break.
Nickel cast iron valve
Alkali resistance than gray cast iron, ductile iron valves strong;Nickel cast iron is an ideal valve material for dilute sulfuric acid, dilute hydrochloric acid and caustic soda.
Brass valves
Brass valves have good corrosion resistance to water, seawater, a variety of salt solutions, organic matter.It has good corrosion resistance to sulfuric acid, phosphoric acid, acetic acid and dilute hydrochloric acid without oxygen or oxidant, and good resistance to alkali.However, it is not resistant to the corrosion of oxidizing acids such as nitric acid and concentrated sulfuric acid, nor to the corrosion of molten metals, sulfur and sulfide.Avoid contact with ammonia, which can cause stress corrosion cracking of copper and copper alloys.It should be noted that different grades of copper alloys have different corrosion resistance.