How to Protect FBE Coated Steel Pipes During Welding and Field Joint Coating

Date: 2026-11-13

FBE (fusion-bonded epoxy) coating provides external corrosion protection for steel pipes used in pipeline projects. However, during pipeline construction, the coating near pipe ends must be protected while individual pipe sections are joined by welding. The exposed joint area then requires a suitable field joint coating system. If this work is not properly controlled, damage or poor bonding at the joint can compromise the continuity of the pipeline's corrosion protection. Protecting the factory coating and applying the correct field joint system are therefore important parts of pipeline construction.

Why Are Field Joints Important in an FBE Coated Steel Pipeline?

Factory-applied FBE coating normally stops short of the pipe ends, leaving a specified cutback area for welding. Once two pipe sections are joined, the exposed weld area and adjacent bare steel need corrosion protection. The field joint coating must cover the prepared joint area and overlap the existing mainline coating as required by the approved procedure. Its compatibility with the factory-applied FBE, operating conditions and installation requirements should be confirmed before construction begins.

1. Confirm the Field Joint Coating System Before Welding

The field joint coating material and application procedure should be approved before pipeline welding starts. The selected system may include liquid-applied coatings, heat-shrink sleeves or other qualified field joint solutions. The choice depends on the project specification, operating temperature, pipeline environment and installation conditions. Before work begins, confirm:

Compatibility with the factory-applied FBE coating.
Required cutback and overlap dimensions.
Surface preparation and application procedures.
Environmental and curing requirements.
Inspection, repair and acceptance criteria.

Using an ordinary epoxy product without checking its suitability and compatibility can lead to adhesion or long-term performance problems.

2. Protect the Factory Coating During Welding

Welding heat, sparks, spatter and handling tools can damage the coating close to the pipe ends. The specified cutback should provide sufficient clearance for welding while preserving the factory coating outside the preparation area. During welding, personnel should avoid unnecessary contact between hot materials, tools and coated surfaces. Suitable handling and positioning equipment should also be used to prevent scratches, impact damage and abrasion. After welding, the completed weld should undergo the required inspection and acceptance checks under the project specification. Field joint coating should not begin until the weld has been accepted and released for surface preparation. Weld inspection and coating inspection are separate quality control activities, and both should be completed at the appropriate stages.

3. Prepare the Joint Surface Correctly

Surface preparation has a direct effect on field joint coating performance. Before application, remove oil, grease, dust, rust, weld spatter and other contaminants from the joint area. The exposed steel should be prepared using the method and cleanliness level specified for the selected coating system. The overlap area on the existing FBE coating may also require controlled abrasion or other specified surface treatment to promote bonding. The preparation method must follow the approved procedure and should not damage sound factory coating beyond the permitted limits. If the existing FBE is chipped, cracked or otherwise damaged, the affected area should be assessed and repaired using an approved method before the field joint coating is applied.

4. Apply the Field Joint Coating Under Controlled Conditions

Field joint coating should be applied by trained personnel in accordance with the approved procedure and material manufacturer's instructions. Important control points include:

Ambient and steel surface temperature.
Relative humidity and dew point conditions.
Surface cleanliness and preparation profile.
Coating application thickness and overlap.
Curing time and handling restrictions.

Application should only proceed when environmental conditions meet the requirements of the approved procedure. Generic temperature, humidity or curing values should not replace the qualified requirements for the selected coating system.

5. Inspect and Repair the Completed Joint

After application and curing, the completed field joint should be inspected according to the project Inspection and Test Plan (ITP). Depending on the coating system and project specification, inspection may include visual examination, coating thickness measurement, holiday detection, adhesion testing or other specified checks. Any unacceptable defect should be identified, repaired and retested according to the approved repair procedure. Inspection records should maintain traceability to the pipe joint and include relevant coating material batches, inspection results and repair status.

Common Field Joint Coating Problems

Several problems can affect the quality of field joint protection:

Insufficient overlap: The field joint coating does not extend adequately onto the prepared factory coating.
Poor surface preparation: Oil, dust, rust or unsuitable surface conditions reduce coating adhesion.
Incorrect application conditions: Temperature, humidity or curing conditions fall outside the approved procedure.
Mechanical damage: Handling or backfilling damages the completed coating.
Unrecorded repairs: Missing repair and retest records make final acceptance more difficult.

These issues can be reduced through approved procedures, trained applicators, proper handling and clearly defined inspection responsibilities.

FAQ

Q1. Why are FBE coated pipe ends left uncoated?
A1: A specified cutback leaves sufficient space for welding. After the weld is accepted, the exposed area is protected using an approved field joint coating system.

Q2. Is field joint coating always made of FBE?
A2: No. Field joint systems may use liquid-applied coatings, heat-shrink sleeves or other qualified materials. The selected system must meet project requirements and be compatible with the mainline coating.

Q3. Can ordinary epoxy paint be used for FBE field joint repair?
A3: Not automatically. The repair material must be approved for the intended application and compatible with the existing FBE coating.

Q4. Should field joints undergo holiday detection?
A4: Holiday detection should be performed when required by the project specification and applicable coating procedure. The test method and voltage must be suitable for the coating system and thickness.

Q5. Which standard covers pipeline field joint coating?
A5: ISO 21809-3:2016, including Amendment 1:2020, covers field joint coating qualification, application and testing for relevant buried and submerged pipeline systems in the oil, gas and petrochemical industries. The applicable edition and project requirements should be confirmed before construction.

FBE Coated Steel Pipe Supply for Pipeline Projects

Hunan Great Steel Pipe Co., Ltd. supports FBE coated steel pipe supply for pipeline projects through material sourcing, production coordination, coating inspection arrangements, documentation review and export delivery coordination. For projects involving field joint coating, mainline coating requirements, pipe-end cutback dimensions and applicable inspection documents can be reviewed as part of the project supply coordination process.

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Tags : FBE steel pipe field joint coating , FBE pipe welding protection , field joint coating , FBE coating repair , FBE field joint inspection

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