NACE SP0185-2024
Extruded Two-Layer Polyolefin Resin Coating Systems with Adhesives for Underground or Submerged Pipe
- Standard No.
- NACE SP0185-2024
- Release Date
- 2024
- Published By
- National Association of Corrosion Engineers (NACE) US / NACE
- Latest
- NACE SP0185-2024
- Introduction
Standard Overview and Technology Evolution
NACE SP0185-2024, revised and released by the Association for Materials Protection and Performance (AMPP) on January 29, 2024, is the authoritative technical specification for extruded two-layer polyolefin resin coating systems for underground or underwater pipelines. The standard dates back to the approved version of NACE TG T-10D-12 in 1985. After multiple revisions in 1996 and 2007, the 2024 edition primarily includes editorial changes, eliminating redundant language and clarifying the functional descriptions of primary and secondary means of corrosion protection.
Coating system types and technical characteristics
This standard specifies two types of extruded polyolefin resin coating systems in detail:
Characteristic parameters Type A system (cross-linked extrusion) Type B system (spiral extrusion) Application method Polyolefin resin is extruded by cross-linking to form a seamless coating on the pipe Polyolefin resin is spirally extruded and fused around the pipe to form a seamless coating Adhesive type Hot-applied asphalt-based adhesive (a mixture of asphalt, rubber and polymer resin) Extruded butyl rubber adhesive Minimum thickness requirement Adhesive ≥ 0.254mm, Polyolefin ≥ 0.762mm, Total System ≥ 1.016mm Adhesive ≥ 0.254mm, Polyolefin ≥ 0.762mm, Total System ≥ 1.016mm Peel Adhesion ≥ 21N/10mm width (12.0lbf/in width) ≥ 21N/10mm width (12.0lbf/in width) Cathodic Disbonding ≤ 12mm radius (-1.5V/28 days) ≤ 8mm radius (1.5V/3%/21°C/28 days) Impact Resistance ≥29,477.5cm-g/mm ≥29,477cm-g/mm Both systems utilize a two-layer design: a bottom adhesive layer and a top polyolefin protective layer. The polyolefin layer can be made of high-density, low-density, medium-density polyethylene, or a mixed bimodal polyethylene, providing excellent mechanical and corrosion protection for the pipe.
Key Technical Requirements for Surface Preparation
Surface preparation quality directly impacts the long-term performance of the coating system, and this standard sets strict requirements:
Carbon steel pipe must be abrasive blast cleaned to meet the requirements of NACE No. 3/SSPC-SP 6, with a surface profile of 38-90μm (1.5-3.5mil). During abrasive blasting, the pipe surface temperature must be at least 3°C above the dew point and the relative humidity must be ≤80%. Ductile iron pipe must be cleaned by sandblasting or wire brushing to remove debris, but the surface profile generated by the pipe mill process must not be altered. This should be done in accordance with NAPF 500-03 or the coating manufacturer's recommended procedures. The coating must be applied within 8 hours of cleaning, ensuring that the surface condition conforms to the parameters established during the original cleaning. Grooves, end faces, and internal coatings must be protected from sandblasting damage, and sandblasting residue must be completely removed from both the interior and exterior pipe surfaces. Preheating Requirements: Preheating the pipe prior to application may be necessary, according to the coating manufacturer's specifications, to ensure optimal bonding between the adhesive and the polyolefin layer. Adhesive should be applied at the manufacturer's recommended temperature parameters to a minimum thickness of 250μm (10 mils). The polyolefin resin sheath is extruded over the adhesive to the specified thickness by cross-linking.
Type B System Application
Butyl rubber adhesive is applied at the manufacturer's recommended temperature parameters to a minimum thickness of 250 μm (10 mils). Overlapping layers of butyl rubber adhesive are spirally extruded around the pipe with a minimum overlap of 6.4 mm (0.25 in). Immediately thereafter, overlapping layers of polyolefin resin are spirally extruded around the pipe to the specified thickness and fused with a minimum overlap of 13 mm (0.50 in) to form a seamless coating.
For pipes with prominent welds, such as double submerged arc welded (DSAW) pipe, precautions should be taken to avoid voids in the coating beneath the weld. In such cases, a cold-applied soft tape system should be applied along the longitudinal weld, using a pressure roller to prevent air entrapment. Alternatively, the weld may be ground or sanded to smooth its contour according to the pipe manufacturer and owner's specifications.
Cooling
The coated pipe should be cooled by water quenching or other cooling methods as recommended by the pipe or coating manufacturer before handling and inspection to minimize coating damage.
Quality Inspection and Acceptance Criteria
Thickness Measurement
The coating thickness shall conform to the specified thickness or as agreed upon between the applicator and the purchaser. In no case shall the adhesive thickness be less than 250 μm (10 mils) and the polyolefin resin thickness not less than 760 μm (30 mils). Thickness measurements shall be made using applicable techniques such as ASTM D7091 and within the tolerances stated for the specific instrument used.
Leak Detection
After coating application, all coated pipes shall be 100% high-pressure inspected in accordance with NACE SP0274 immediately.
Field Adhesion Testing
The coating system shall be tested for adhesion at a 180° peel angle in accordance with a modified ASTM D1000. The test shall be modified to use a steel surface prepared in accordance with this standard and include a 24-hour dwell time in which the coating system remains in contact with the substrate. Testing should be conducted within the temperature range of 18-29°C. If testing is conducted outside this temperature range or the 24-hour dwell time is not achieved, but the test sample meets the required values, the sample is deemed to meet the peel adhesion requirements of this standard.
Testing frequency shall be: first pipe, every tenth pipe, and last pipe of each production batch, or as specified by the purchaser.
Repair Techniques and Quality Control
Leaks and areas of coating damage shall be repaired at the applicator's facility using compatible materials and applied in accordance with the manufacturer's recommendations. Recommended repair material types and methods include:
- Cold application tape
- Heat shrink sleeves
- Hot patches
- Stripping and recoating as recommended by the coating manufacturer (as recommended by the applicator and approved by the purchaser)
Surface preparation shall ensure that the entire affected area is properly prepared and coated. The pipe surface in the area to be repaired and adjacent coating surfaces shall be clean, dry, and free of all millwork preservatives and foreign matter. All sharp edges and unadhered coating should be removed. The surface to be coated should be abraded as specified by the purchaser. If the outside temperature is below 10°C (50°F), the prepared surface should be preheated before applying the primer or coating material. Manufacturer's recommendations should be followed.
The entire repair area should be electrically tested in accordance with NACE SP0274.
Handling and Storage Specifications
Coated pipe requires special considerations during handling, loading, and storage:
Handling Requirements
Coated pipe should be handled to prevent coating damage using wide, non-metallic canvas or leather slings, end hooks, or other devices designed to protect the coating and pipe.
Loading Specifications
Transportation equipment should be used to prevent coating damage. All pipe supports should have adequate padding to prevent damage. Ties, straps, and slings may require padding. Truck trailers should have shields to protect the coating from rocks and should be free of obstructions that could damage the coating. Adequate clearance must be maintained between coated pipe and truck exhaust pipes.
Storage Conditions
Storage areas should be free of rocks, stones, branches, and other protrusions and be well drained. Contact areas of racks, skids, or rails should be padded (e.g., rubber, canvas, tape, fiberboard, or other suitable material). If earth or sand dikes are used, they should be free of debris and objects that could damage the coating. Plastic sheeting should separate the dikes from bare or coated pipe.
Coated pipe may be stacked, using methods such as pyramid or nested stacking and strip stacking. The height of the pipe stack (i.e., the number of pipe layers) is affected by variables such as pipe diameter, wall thickness, coating thickness, ambient temperature, and safety.
Extruded polyolefin resin-coated pipe may be stored outdoors for at least 6 months if chemical UV absorbers are added to the resin (see Section 4.4).
Implementation Recommendations and Engineering Applications
Material Selection Considerations
When selecting a Type A or Type B system, engineers should consider the following factors:
- Environmental Conditions: Soil corrosivity, groundwater level, microbial activity, etc.
- Operating Temperature: Temperature tolerance range of the polyolefin coating
- Mechanical Stress: Tensile, bending and impact loads during installation
- Cathode Protection Compatibility: Synergy between the coating system and the cathodic protection system
Quality Control System
It is recommended to establish a comprehensive quality control system, including:
- Raw Material Batch Traceability System
- Surface Treatment Process Monitoring
- Online Coating Thickness Detection
- Regular Adhesion Sampling Test
- Standardization of Repair Process
Technical Training Requirements
Coating operators should receive professional training, including:
- Understanding and practice of surface treatment standards
- Extrusion equipment operation and maintenance
- Coating thickness control technology
- Use of leak detection instruments
- Repair material application methods
Through systematic training and practical assessment, ensure that coating quality meets the requirements of NACE SP0185-2024 and provides long-term, reliable corrosion protection for underground and underwater pipelines.
Standard Development Trends and Outlook
With the continuous development of material technology and testing methods, polyolefin coating system standards will continue to evolve. Possible future development directions include:
- Inclusion standards for new polyolefin materials
- Intelligent coating thickness monitoring technology
- Development of environmentally friendly adhesives
- Improvement of accelerated aging test methods
- Application of digital quality traceability systems
Engineering practice has shown that polyolefin coating systems that strictly implement the requirements of the NACE SP0185-2024 standard, under correct design and construction conditions, can provide more than 30 years of effective corrosion protection for underground and underwater pipelines, significantly extending the service life of pipelines and reducing maintenance costs.
NACE SP0185-2024 Referenced Document
- API RP 5L1 Recommended Practice for Railroad Transportation of Line Pipe
- ASTM D1000 Standard Test Method for Pressure-Sensitive Adhesive-Coated Tapes Used for Electrical and Electronic Applications
- ASTM D1238 Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer
- ASTM D149 Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
- ASTM D1505 Standard Test Method for Density of Plastics by the Density-Gradient Technique
- ASTM D2240 Standard Test Method for Properties of Rubber &8212; Durometer Hardness*， 2026-06-06 Update
- ASTM D570 Standard Test Method for Water Absorption of Plastics
- ASTM D638 Standard Test Method for Tensile Properties of Plastics
- ASTM D7091 Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals
- ASTM D71 Standard Test Method for Relative Density of Solid Pitch and Asphalt (Displacement Method)
- ASTM E28 Standard Test Methods for Softening Point of Resins Derived from Naval Stores by Ring-and-Ball Apparatus
- ASTM E96 Standard Test Method for Water Vapor Transmission of Materials
- ASTM G14 Standard Test Method for Impact Resistance of Pipeline Coatings (Falling Weight Test)
- ASTM G17 Standard Test Method for Penetration Resistance of Pipeline Coatings (Blunt Rod)
- CSA Z245.21 Plant-applied external polyethylene coating for steel pipe
- NACE No. 3 Joint Surface Preparation Standard Commercial Blast Cleaning Item No. 21067; SSPC SP 6 1999
- NACE SP0274 High Voltage Electrical Inspection Pipeline Coating Practice*， 2026-06-06 Update
NACE SP0185-2024 history
- 2024 NACE SP0185:2024 Extruded Two-Layer Polyolefin Resin Coating Systems with Adhesives for Underground or Submerged Pipe
- 2007 NACE SP0185-2007 Extruded Polyolefin Resin Coating Systems with Soft Adhesives for Underground or Submerged Pipe (Item No. 21029)
- 1996 NACE RP0185-1996 Extruded Polyolefin Resin Coating Systems with Soft Adhesives for Underground or Submerged Pipe
