Inspection Standards for FBE Anticorrosive Coatings

FBE (Fusion-Bonded Epoxy) anticorrosive coating inspection standards encompass international, national, and industry specifications, focusing primarily on coating performance parameters and acceptance requirements. Below is a detailed overview of the core standard systems and key technical indicators:

I. International Standard System

1. ISO 21809 Series
   1. ISO 21809-1:2018: Specifies that the FBE primer layer thickness in 3-layer polyethylene (3LPE)/polypropylene (3LPP) coatings shall be ≥300μm, with adhesion ≥5MPa.
   1. ISO 21809-11:2019: Requires field joint and repair coatings to match the original coating thickness and pass the cathodic disbondment test (65°C, 28 days) with a disbondment distance ≤10mm .
   1. ISO 12944-6: Salt spray testing (ISO 9227) mandates that FBE coatings withstand 1,000 hours of testing without blistering or rusting .
2. ASTM Standards
   1. ASTM D4541-22: Adhesion testing requires a pull-off strength ≥5MPa and a loading rate of 0.8MPa/s ±10% .
   1. ASTM G42-11: High-temperature cathodic disbondment testing (80°C, 0.5MPa) allows a maximum disbondment distance of ≤15mm .
   1. ASTM A 775/A 775M: General standard for epoxy coatings, specifying requirements for coating thickness, adhesion, and continuity.
3. NACE SP0169-2024
   1. Coating insulation resistance ≥10,000Ω·m², with a cathodic protection potential ≤-0.85V (vs CSE) .

II. Chinese National Standards

1. GB/T 39636-2020 (Core Standard)
   1. Thickness: Single-layer FBE: 350μm ±50μm; double-layer FBE: total thickness ≥600μm, with local minimum thickness ≥80% of the design value.
   1. Adhesion: Pull-off strength ≥5MPa; cross-cut method grade ≥2 (GB/T 9286-2021) .
   1. Cathodic Disbondment: Disbondment distance ≤15mm after testing at 65°C for 28 days .
2. GB/T 4956-2003
   1. Thickness measurement accuracy for magnetic substrates: ±10μm, with at least 3 measurements per square meter .
3. GB/T 5210-2006
   1. Pull-off test requires a specimen diameter of 20mm ±0.5mm and surface preparation to Sa2.5 grade.

III. Industry Standards

1. SY/T 4113.11-2023 (Replacing SY/T 0063-1999)
   1. Holiday Detection: High-voltage spark testing voltage calculated as  V = 7900\sqrt{T}  (T = thickness in mm), with a typical value of 2.1kV (0.4mm thickness) and a holiday density ≤2 defects/m² .
   1. Low-Voltage Detection: DC voltage ≤100V, used to detect thickness deficiencies .
2. SY/T 0315-97
   1. Double-layer FBE total thickness ≥600μm, requiring passage of a 1.5J impact test and 3° bend test without disbondment .
3. SY/T 7036-2016
   1. Compatibility requirements for coatings and cathodic protection in oil and gas station pipelines: current density ≤10μA/cm² .

IV. Special Scenario Standard Requirements

1. High-Temperature Environments
   1. Hot oil pipelines must pass the ASTM G42 test (80°C, 0.5MPa) with a disbondment distance ≤15mm .
   1. Glass transition temperature (Tg) must exceed 80°C, verified via DSC testing.
2. Buried Pipelines
   1. Coating insulation resistance ≥10,000Ω·m², with a cathodic protection potential ≤-0.85V (vs CSE).
   1. Combined with Close Interval Potential Survey (CIPS) to assess defect distribution.
3. Repair Projects
   1. Repaired areas must meet thickness, adhesion, and holiday detection requirements, with interface bond strength ≥4MPa.

V. Surface Preparation and Calibration Specifications

1. Surface Preparation Standards
   1. Sandblasting cleanliness grade must reach Sa2.5 (GB/T 8923.1) or SSPC-SP 10 (near-white grade).
2. Equipment Calibration
   1. Thickness Gauges: Calibrated using standard test blocks (e.g., 350μm ±5μm), with an error ≤±5%.
   1. Spark Testers: Verified daily using calibration plates with artificial defects, ensuring voltage error ≤±2%.
3. Reporting Requirements
   1. Test data must include location, equipment model, calibration records, and bear CMA/CNAS accreditation stamps.

Through this standard system, the thickness, adhesion, corrosion resistance, and compatibility with cathodic protection of FBE anticorrosive coatings can be comprehensively evaluated, ensuring long-term reliability in oil & gas, chemical, and other industrial applications.