How to avoid corrosion of welded pipes

Posted by chase Liu on November 4th, 2022

Methods to avoid corrosion of welded steel pipes

1) Pipe surface treatment

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

2) External anti-corrosion design of pipeline

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

3) Anti-corrosion design in pipeline

Different anti-corrosion processes need to be selected according to the different conveying medium for the internal anti-corrosion of welded pipes. 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 metal 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 a combination of sacrificial anode cathodic protection and anti-corrosion coating, which is widely used in anti-corrosion engineering with good results.