Pipeline corrosion protection

Pipeline corrosion protection employs techniques such as coating and cathodic protection to mitigate corrosion caused by soil, atmospheric conditions, and the transported media. Its primary objectives are to extend pipeline service life and prevent leaks and environmental contamination.

Mainly adopted corrosion protection methods

1. Coating-based corrosion protection: Applying a protective coating to the pipe surface to isolate it from corrosive media is the most fundamental method.

  - 3PE Corrosion protection: Composed of a three-layer structure—an epoxy powder primer, an intermediate adhesive, and an outer polyethylene layer—it exhibits excellent corrosion resistance and mechanical damage resistance, with a design service life of up to 30-50 Year.

  -  Epoxy coal tar pitch: high strength, excellent insulation, and resistant to water and heat; however, it has a long curing time and is significantly influenced by environmental conditions.

  -  Polyethylene coating: A specialized machine is used to thermoplastically apply polyethylene to the pipe surface, forming a continuous, rigid plastic outer shell.

2. Cathodic protection: Electrochemical techniques are used to render the pipe surface cathodic, thereby preventing corrosion.

  -  Sacrificial anode method: A more chemically active metal (such as magnesium or an aluminum alloy) is attached to the pipeline, allowing the anode to corrode while protecting the pipeline.

  -  Impressed‑current method: An external DC power source is used to polarize the pipeline metal as a cathode, thereby providing protection.

3. Joint Protection: In practical engineering, a dual protection system combining coating-based corrosion protection with cathodic protection is commonly employed.

Common anticorrosion materials

1.  Traditional materials: petroleum asphalt, coal‑tar enamel, and the like—once widely used but associated with significant environmental pollution—have gradually been replaced.

2.  Mainstream materials include epoxy powder, polyethylene, and epoxy coal tar pitch, among which… 3PE Anti-corrosion is currently the mainstream technology for external corrosion protection of underground pipelines.

3.  Internal anti-corrosion materials: For potable water pipelines, cement mortar lining is commonly used; for sewage pipelines, epoxy coal tar coatings or liquid epoxy coatings may be employed.

4.  New materials—such as phenolic‑epoxy coatings and ceramic‑filled coatings—are being increasingly adopted; when selecting these, it is essential to prioritize environmental friendliness and zero pollution.

Key requirements during construction

1.  Surface preparation: Prior to corrosion protection, the pipe surface must be thoroughly cleaned of moisture, oil, dirt, rust, and scale. Manual rust removal shall achieve… St3 Grade, sandblasting or chemical derusting shall reach Sa2.5 Level.

2.  Environmental Control: During the application of the anti-corrosion coating, the ambient temperature shall be higher than 5 ℃, with air humidity below 80% , the treated surface shall be 4  Apply the primer within the hour.

3.  Quality Inspection: The anti-corrosion coating shall undergo a voltage test; standard grade. 2000V , Enhanced Level 2500V , Extra-Strong Grade 3000V , each 10 km The number of leakage points shall not exceed 5  Place.

4.  Joint repair: The pipe joint‑repair material must be compatible with the main anti-corrosion coating. 3PE The preferred choice for the main anti-corrosion layer is a three-layer system. PE Heat-shrinkable joint‑repair material.

Anti-corrosion pipeline

Anti-corrosion pipelines are steel or metal pipes that have undergone anti-corrosion treatment, employing techniques such as coating, cladding, or electrochemical protection to prevent corrosion in soil, water, air, or the conveyed medium, thereby significantly extending their service life.

Classification and Distinction

1.  By base material: Seamless anti-corrosion steel pipes, spiral-welded anti-corrosion steel pipes, straight-seam anti-corrosion steel pipes, and others—though the base materials differ, their anti-corrosion processes are similar.

2.  According to the anti-corrosion structure:

   - 3PE Anti-corrosion steel pipe: the most commonly used, with a three-layer structure—epoxy powder coating as the inner layer. (FBE) , intermediate adhesive, outer polyethylene layer (PE) , the thickness of the external anti-corrosion coating can reach 2.5-4mm , corrosion-resistant, impact-resistant, and long-lasting.

   - FBE Epoxy powder coating: single‑ or double‑layer epoxy powder coatings, offering strong adhesion but with a relatively higher water absorption rate.

  -  Epoxy coal tar pitch anti-corrosion coating: available in standard, enhanced, and extra‑enhanced grades; it is relatively inexpensive but has a long curing time and is highly susceptible to environmental factors.

   - IPN8710 Corrosion protection: Commonly used for internal wall protection; non-toxic, water-resistant, and corrosion-resistant, suitable for potable water pipelines.

- TPEP Yes 3PE the improved type (typically referring to internally fused epoxy) +  Outside 3PE Structure), non-independent foundation classification.

3.  By purpose: Oil and natural gas pipelines, water supply and drainage pipelines, gas pipelines, chemical pipelines, heating pipelines, and others.

Material selection:

-  Underground oil and gas pipelines: prioritize selection of 3PE Anti-corrosion steel pipes feature a highly durable external coating with excellent mechanical strength and electrical insulation, allowing them to be directly buried underground or submerged in water.

-  Potable water piping: inner wall optional IPN8710 Anti-corrosion or fusion-bonded epoxy powder shall comply with hygiene standards.

-  Gas pipeline: New high-pressure line / High-pressure pipelines must be equipped with a corrosion‑protective coating and a cathodic protection system, while aging medium- and low-pressure pipelines require close attention to the degradation of their protective coatings.

-  Chemical corrosion media: Select epoxy resin, polyurethane, ceramic coatings, etc., based on the medium’s acidity, alkalinity, and salinity characteristics.

-  In severely cold regions, insulation measures must be employed; in areas such as Northeast China, thermal expansion and contraction during winter can cause pipes to freeze and crack.

Construction Acceptance

-  Surface treatment is critical: rust removal must reach Sa2.5 Grade (sandblasting or chemical derusting), surface roughness 30 ~ 50 mu m More suitable, after processing 4 The primer must be applied within the hour.

-  Anti-corrosion coating application: 3PE And the epoxy powder requires preheating the steel pipe to 250-300 ℃, causing the powder to melt and form a continuous coating on the tube wall.

-  Joint‑filling material: the main component is 3PE Yes, the three-layer option is the first choice for repair. PE Heat-shrink joint‑repair material; single‑layer epoxy powder can be used with epoxy powder and adhesive tape. + Primer, etc.

-  Acceptance testing includes grid‑cutting tests (adhesion tests), spark‑testing, thickness measurements, and other procedures; the anti‑corrosion coating of underground pipelines must be inspected periodically.

-  Cathodic protection: Buried steel pipelines are often used in conjunction with anti-corrosion coatings, and it can be implemented either by the sacrificial anode method or the impressed current method.

2PE/3PE/TPEP Comprehensive Quick-Reference Chart for Selecting Corrosion-Resistant Pipes

Key Considerations for Selection Decisions

If the conveyed medium is a mild fluid such as natural gas or tap water, prioritize selecting… 3PE , can save 20%-30% The cost.

When conveying strong acids, strong alkalis, or fluids containing solid particles, prioritize selecting… TPEP , avoid frequent maintenance.

For temporary or low‑requirement applications such as wastewater tanks and steel structure protection, epoxy coal tar pitch offers the best cost‑effectiveness.