A kind of preparation method of strong acid and strong alkali resistant nodular cast iron pipe

Abstract

The invention discloses a method for preparing a ductile cast iron tube with strong acid and alkali resistance. The method comprises the following steps: (1) performing ball blast treatment on the surface of a ductile cast iron tube substrate; (2) spraying a stainless steel alloy bottom layer; and (3) coating an anti-corrosion coating layer on the outer surface of the ductile cast iron tube with the stainless steel alloy bottom layer. The method provided by the invention is used for reducing the uniform corrosion speed of the stainless steel alloy. on the basis of a formed synergetic anti-corrosion system of the stainless steel alloy bottom layer and the anti-corrosion coating layer, the ductile cast iron tube still has excellent anti-corrosion property under the conditions of lower pH value (PH<4) and higher PH value (PH<12), thereby greatly prolonging the service life of the ductile cast iron tube under strong acid and alkali conditions.

Description

technical field [0001] The invention relates to a preparation method of a ductile iron pipe resistant to strong acid and strong alkali. Background technique [0002] Ductile iron pipes have always been made of zinc as the base, and then sprayed with a sealing layer on the composite anti-corrosion system ductile iron pipes. This is a sacrificial anode plus cathodic protection anti-corrosion system. It has the advantage of long anti-corrosion years and has been satisfied by users Well received and widely used all over the world. However, some problems were also found in use. For example, after the application of zinc-sprayed bottom layer + asphalt topcoat coating ductile iron pipe in a coastal Guangdong area, a perforation and water leakage accident occurred in just two or three years. After various studies and analysis, The main cause of the accident was found. First, the soil was highly acidic, with a pH of 5.5 (water extract) after testing. Second, Cl - Ions and SO4 2- H...

AI Technical Summary

Problems solved by technology

The aluminum sprayed coating has good corrosion resistance in the environment medium of PH=4~9. In the case of low pH value (P﹤4) and high pH value (PH﹥12), the aluminum-zinc sprayed coating None of them can play a good anti-corrosion effect. In addition, in the environment of > 60 ℃, the potential of the zinc layer exceeds the potential of the iron layer, and the protective effect of the sacrificial anode is lost.

[0004] The pH of the soil in the pipe explosion area of ​​Guangdong is about 5.5, which is beyond the use range of zinc coating with a pH of 6 to 12. If zinc-sprayed bottom layer + asphalt topcoat coating ductile iron pipes are still used, the corrosion of ductile iron pipes will be accelerated, and the short-term perforated squib

Images