Wetting penetrants and surfactants have close ties in the field of chemistry, but there are also some differences between them. Below is a detailed comparison of these two concepts. I. Definitions and Classifications Wetting Penetrants Wetting penetrants are substances that can reduce the liquid-solid interfacial tension, increase the contact of liquid with solid surfaces, or enhance the wetting and spreading of liquids on solid surfaces. They typically have specific chemical structures, such as alkylphenol ethoxylates and fatty alcohol ethoxylates, which give them wetting and penetrating properties. Surfactants Surfactants are substances that, when added in small amounts, can significantly change the interfacial state of a solution system. They have fixed hydrophilic and lipophilic groups and can orient themselves at the solution surface. Based on their molecular structures, surfactants can be classified into ionic surfactants (including cationic and anionic surfactants), non-i...