Anti-corrosion of black carbon steel pipe

In the industrial sector, black carbon steel pipe is a widely used and crucial material. However, steel pipes are prone to corrosion, which can significantly shorten their lifespan. To protect black carbon steel pipes from corrosion, appropriate anti-corrosion measures are essential.

1. Methods for External Anti-Corrosion of Black Carbon Steel Pipe

Using cathodic protection alone is not cost-effective due to its high power consumption. Therefore, combining an anti-corrosion layer with cathodic protection is the best and most economical form of protection. This "combined protection" method focuses cathodic protection on the exposed metal surface at defects in the anti-corrosion layer, primarily using the anti-corrosion layer with cathodic protection as a supplement.

2. Internal Anti-Corrosion Treatment of Black Carbon Steel Pipe

The main anti-corrosion measures for internal treatment include the anti-corrosion layer and cathodic protection. The anti-corrosion layer serves as a barrier to control metal corrosion. However, exposed metal at defects can form a local corrosion cell with the surrounding anti-corrosion layer, accelerating the corrosion rate of the exposed metal. Therefore, relying solely on the anti-corrosion layer is not ideal. A combination of an anti-corrosion layer and cathodic protection should be employed.

3. External Anti-Corrosion Materials for Black Carbon Steel Pipe

Pipeline anti-corrosion materials are designed to inhibit chemical and electrochemical corrosion. These materials are divided into those for the pipeline body and corresponding patching materials. Main anti-corrosion materials include:

Pipeline Body Materials: Petroleum asphalt, epoxy coal tar, adhesive tape, epoxy powder, PE coating, PP coating.

Patching Materials: Petroleum asphalt patching, epoxy coal tar patching, adhesive tape patching, epoxy powder patching, PE heat shrink material patching.

4. Surface Treatment

(1) Surface Treatment for Anti-Corrosion Coating of Steel Pipes

Steel pipes often have contaminants such as dust, oil, oxide scale, rust, pollutants, salt, or old paint. Oxide scale, a dense oxide layer formed at high temperatures, is common but often overlooked. It acts as a cathode, accelerating metal corrosion. If these contaminants are not removed before applying anti-corrosion coatings, the adhesion and effectiveness of the coating will be compromised. Statistics indicate that over 70% of paint failures are due to improper surface preparation. Therefore, appropriate surface treatment is crucial for the performance of metal anti-corrosion coatings.

(2) Steel Pipe Anti-Corrosion Surface Cleaning Levels

There are two prominent international standards for surface cleaning levels:

SSPC-: Established by the United States in 1985.

Sa-: Developed by Sweden in 1976, with four levels: Sa1, Sa2, Sa2.5, and Sa3, which are widely recognized international standards.

In summary, selecting the appropriate anti-corrosion measures and materials, along with proper surface preparation, is vital for extending the service life and maintaining the integrity of black carbon steel pipes in industrial applications.