Passivation is due to the interaction between the metal and the oxidizing properties, and a very thin, dense, good covering performance, and a passivation film firmly adsorbed on the metal surface are formed on the metal surface. This film exists in phases, usually compounds of oxidized metals. It plays the role of completely separating the metal from the corrosive medium, preventing the metal from contacting the corrosive medium, so that the metal basically stops dissolving and forms a passive state to prevent corrosion.

Anti-corrosion steel pipe base materials include spiral pipes, straight seam pipes, seamless pipes, etc. Widely used in pipeline engineering fields such as long-distance water transmission, petroleum, chemical industry, natural gas, thermal power, sewage treatment, water source, bridge, steel structure, marine water transportation piling, etc.

Electric resistance welded steel pipes, referred to as ERW pipes, have many advantages such as high productivity, low cost, high dimensional accuracy and beautiful appearance. In recent years, countries are actively researching the use of ERW steel pipes instead of seamless steel pipes and spiral seam welded steel pipes.

Ultrasonic testing of seamless pipes uses ultrasonic technology for testing and is one of the five conventional nondestructive testing methods. Ultrasonic testing is a method for inspecting parts for defects due to the characteristics of reflection at the edge of the interface when sound energy penetrates deep into the metal material and passes from one section to another. When the ultrasonic beam passes from the surface of the steel pipe through the probe to the inside of the metal, when it encounters a defect and the bottom surface of the steel pipe, reflected waves will occur respectively, and a pulse waveform will be formed on the fluorescent screen.

Stainless steel seamless steel pipe is a long strip of steel with a hollow section and no seams around it. It is a steel pipe that is resistant to weak corrosive media such as air, steam, water, and chemically corrosive media such as acid, alkali, and salt.

Steel pipe refers to steel with openings at both ends and a hollow section, and its length is relatively large compared to the surrounding area. According to its production method, it can be divided into seamless steel pipe and welded steel pipe. The specification of the steel pipe is represented by the external dimension and wall thickness, and its size ranges from a small capillary tube to a large diameter tube with a diameter of several meters.