What are the differences in chemical resistance between gaskets made of different materials?

Gaskets made of different materials vary greatly in chemical resistance:

First, rubber material

Natural rubber:

Poor chemical resistance. Some resistance to non-polar solvents (such as gasoline, benzene, etc.), but not resistant to strong acids, strong alkalis, strong oxidizers and other corrosive chemicals. Easily oxidized and corroded, resulting in a decline in sealing performance. For example, when exposed to strong acids such as concentrated hydrochloric acid and concentrated sulfuric acid, natural rubber will be quickly corroded and destroyed.

Nitrile rubber:

Good oil resistance, good resistance to petroleum products, lubricants, etc.. However, it has limited resistance to strong acids, strong bases and polar solvents. For example, it can resist gasoline, kerosene and other oils to a certain extent, but when it comes into contact with strong corrosive chemicals such as sodium hydroxide and sulfuric acid, dissolution and aging will occur.

Fluoroelastomer:

Has excellent chemical resistance. It can withstand a variety of strong acids, strong bases, strong oxidizing agents, organic solvents and other corrosive chemicals.

For example, in contact with nitric acid, hydrofluoric acid, aqua regia and other strong corrosive media, can still maintain good sealing performance. In aerospace, chemical and other fields, the chemical resistance requirements are extremely high occasions, fluorine rubber gasket is a common choice.

Second, the plastic material

Polytetrafluoroethylene (PTFE):

Excellent chemical resistance. Can resist almost all chemicals, including strong acids, strong alkalis, strong oxidizing agents, organic solvents, etc.. Known as the “King of Plastics”. For example, when exposed to various extreme chemicals such as hydrofluoric acid, sodium hydroxide, concentrated sulfuric acid, etc., PTFE gaskets are virtually unaffected. It is widely used in chemical and pharmaceutical industries.

Polyethylene (PE):

General chemical resistance. It has some resistance to acids and alkalis, but is weak to organic solvents.

For example, polyethylene gaskets can be used in dilute acid and alkali solutions, but when exposed to organic solvents such as benzene and toluene, dissolution will occur, resulting in a decline in sealing performance.

Third, metal materials

Copper gasket:

Chemical resistance depends on the specific chemical environment. In general air and water, copper will undergo an oxidation reaction, but the oxide layer can protect copper from further corrosion to a certain extent. Corrosion resistance to non-oxidizing acids (e.g. hydrochloric acid) is poor, while oxidizing acids (e.g. nitric acid) are somewhat resistant. For example, in contact with hydrochloric acid, copper gaskets will be corroded rapidly; but in contact with dilute nitric acid, the corrosion rate is relatively slow.

Stainless steel gasket:

Have good chemical resistance. It is resistant to most acids, alkalis and salt solutions, but corrosion may occur in specific chemical environments, such as solutions containing chloride ions. For example, when exposed to dilute sulfuric acid, sodium hydroxide solution, etc., stainless steel gaskets show good corrosion resistance. However, in seawater, due to the presence of chloride ions, stainless steel may undergo corrosion phenomena such as pitting.