How to avoid corrosion of welded pipe

Ways to avoid corrosion of welded steel tubes

1) Pipe surface treatment

Before the anti-corrosion treatment of welded pipes, the surface of the welded pipe substrate should be treated to remove water, oil, dirt, pollutants, rust and scale on the surface of the substrate. There are many methods of surface treatment, generally using artificial derusting, sandblasting or chemical derusting. For manual derusting, the quality standard should reach St3 level; for sandblasting or chemical derusting, the quality standard should reach Sa2.5 level, and the surface roughness of 30-50 μm is more suitable. The treated surface should be primed within 4 hours;

2) Anti-corrosion design outside the pipeline

Petroleum bitumen coating is the oldest coating and works well in most dry areas. With the development of technology, epoxy coal tar pitch and zinc-rich paint have replaced petroleum pitch as the anti-corrosion paint for steel water pipelines. Due to the excellent anti-corrosion performance and low price of epoxy coal tar pitch series coatings, it has always been the first choice for anti-corrosion coatings for steel water pipelines.

3) Anti-corrosion design inside the pipeline

The internal anti-corrosion of welded pipes needs to choose different anti-corrosion processes according to the different conveying media. The commonly used anti-corrosion processes include cement mortar lining, anti-corrosion coating and plastic lining.

4) Pipeline cathodic protection design

Cathodic protection belongs to electrochemical protection. It is an anti-corrosion technology that uses external current to change the corrosion potential of metals to reduce its corrosion rate. Two methods are usually used, namely sacrificial anode cathodic protection and impressed current cathodic protection. Buried steel pipelines are usually protected by sacrificial anode cathodic protection and anti-corrosion coating, which are widely used in anti-corrosion engineering with good results.

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