Compared with traditional pipes, seamless steel pipes
have lighter raw materials, high strength, good durability, can withstand higher internal pressure, are sensitive in production and use, and can be used in messy or harsh geological conditions. However, there are disadvantages in the use process, mainly because the internal and external anti-corrosion treatment is more troublesome.
The first is the problem of outer wall anti-corrosion. The quality of outer wall anti-corrosion directly affects the service life. At present, the outer wall anti-corrosion of domestic steel pipes is mainly: concealed method, steel pipes are required to be reinforced or specially reinforced outer wall anti-corrosion, and cathodic protection is promoted in some areas. The common anti-corrosion methods for outer walls include coatings such as petroleum pitch and epoxy coal pitch. The latter is not easy to solidify at low temperatures, and there are many problems during field welding. In the past, chlorosulfonated polyethylene was used because of the large amount of solvents. , Prone to pinholes, unqualified resistance to breakdown, and no longer used in some areas. The anticorrosion effect of cathodic protection is better, but because the method of sacrificial anode is selected, the anode needs to be replaced regularly in the future operation, which increases the operating cost and operation.
There are three commonly used methods for the inner wall treatment of seamless steel pipes (astm a106 seamless
): anti-corrosion paint, resin mortar, and cement mortar. But the three methods have two problems: one is the bond strength of the anti-corrosion layer and the steel pipe. Regarding the two methods of anti-corrosion coating and resin mortar, both the inner and outer walls of the steel pipe need to be derusted before construction, but this is difficult to achieve. Therefore, the rust spots will form the source of delamination in the future, which constitutes corrosion and scaling. The second is that most of the steel pipes are butt-welded on site, and anti-corrosion is performed after welding. It can only be done manually, and the quality is not easy to control. For steel pipes with small diameters, because personnel cannot enter the construction, they cannot perform anti-corrosion treatment, which also creates a hidden danger of future weld damage.