According to the dye composition of penetrant, it can be divided into fluorescent penetrant testing, dye penetrant testing and fluorescent dye penetrant testing, which are represented by I, II and Ш respectively. According to the penetrant removal method, it can be divided into water washing type penetrant testing, lipophilic post emulsifying penetrant testing, solvent removing penetrant testing and hydrophilic post emulsifying penetrant testing, which are represented by A, B, C and D respectively; according to the type of imaging agent, it is divided into dry type Powder imaging agent, water soluble imaging agent, water suspension imaging agent, solvent suspension imaging agent and self imaging were expressed as a, b, c, d, e, respectively. II Cd means solvent removal dye penetrant testing, and the imaging agent is solvent suspension type.
