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Understanding why pipeline coatings fail is as important as knowing how to apply them correctly. Root cause analysis (RCA) of coating failures provides invaluable data that drives continuous improvement in specification, application, and quality control processes. This article examines the most common failure modes and the evidence-based strategies to prevent them.

The Most Common Coating Failure Modes

1. Adhesion Failure

Adhesion failure — either at the coating-substrate interface (adhesive failure) or within the coating itself (cohesive failure) — is the most prevalent failure mode. Primary causes include inadequate surface preparation, surface contamination, application below dew point, or use of an incompatible primer. Peel adhesion tests per ASTM D4541 are the standard diagnostic tool.

2. Holiday Formation

Holidays — discontinuities in the coating film — create focal points for corrosion. They can form during application from spray distance variations, equipment malfunctions, or contamination events. High-voltage holiday detection (spark testing) per NACE SP0188 is mandatory for all buried and submerged pipeline coatings before backfill.

3. Cathodic Disbondment

When a coating has a holiday and cathodic protection is active, the alkaline environment generated at the metal surface can cause the coating to lift from the substrate — a phenomenon known as cathodic disbondment (CD). Polyurea systems with optimal adhesion characteristics show dramatically lower CD rates compared to traditional epoxy coatings under equivalent CP conditions.

Field Investigation Techniques

Effective failure investigation combines visual inspection, holiday detection surveys, adhesion testing, thickness measurements, and laboratory analysis of coating samples. NACE TM0215 provides standardized procedures for coating condition assessment during pipeline excavations. Our technical library includes failure investigation report templates used by our member organizations.

Join our Pipeline Integrity Working Group to participate in collaborative failure analysis programs and access anonymized failure data from across the industry.

No coating system can perform to its rated specifications on a poorly prepared surface. Surface preparation is not a cost to be minimized — it is the foundation upon which the entire service life of the coating depends. Industry data consistently shows that 70–80% of all premature coating failures are attributable to inadequate surface preparation rather than defects in the coating material itself.

Understanding Surface Cleanliness Standards

SSPC (Society for Protective Coatings) and NACE International have established a joint classification system for steel surface cleanliness that serves as the global benchmark. The most common standards applicable to pipeline coating are:

• SSPC-SP 6 / NACE No. 3 (Commercial Blast): Removes all oil, grease, mill scale, and corrosion, leaving at most 33% coverage of staining per unit area. Adequate for immersion-grade epoxy and many polyurea systems.
• SSPC-SP 10 / NACE No. 2 (Near-White Metal Blast): Removes at least 95% of all contaminants, leaving only light discoloration. Required for high-performance FBE and thin-film polyurea.
• SSPC-SP 5 / NACE No. 1 (White Metal Blast): Complete removal of all visible rust, mill scale, and coatings. Specified for submerged and buried service in aggressive soils.

Blast Media Selection

Angular steel grit creates a higher anchor profile — measured in mils — than spherical shot, making it the preferred blast media for polyurea applications requiring anchor profiles of 2.5–4.5 mils. Aluminum oxide and garnet are non-recycled alternatives commonly used in field operations where contamination of the blast media is a concern.

Dew Point and Humidity Controls

Steel must be dry and above the dew point temperature before coating application. The standard requirement is that the steel surface temperature be at least 5°F above the dew point at all times during application and initial cure. Dehumidification tents are standard practice for buried pipeline field joint work in humid climates.

For a complete specification template covering surface preparation requirements for polyurea pipeline coatings, visit our resources library. You can also connect with certified applicators in your region who specialize in field preparation.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) has issued a Notice of Proposed Rulemaking (NPRM) that would update coating performance requirements for onshore hazardous liquid pipelines under 49 CFR Part 195. The proposed changes reflect advances in coating technology and a decade of performance data collected under the current regime.

What’s Changing

The proposed rule would introduce minimum peel strength requirements, mandatory holiday testing procedures, and new specifications for field joint coating systems applied in trench conditions. It also proposes a performance-based pathway that allows operators to qualify novel coating materials — including spray polyurea and polyaspartic systems — through third-party testing rather than prescriptive specification compliance.

Industry Response

The oil pipeline coatings industry has broadly welcomed the performance-based pathway, noting that current prescriptive standards have struggled to keep pace with rapidly evolving materials chemistry. Several member organizations submitted comments highlighting their experiences with polyurea systems that meet or exceed the proposed performance benchmarks by wide margins.

Our organization submitted detailed technical comments to the PHMSA docket and will be presenting findings at the Annual Pipeline Integrity Summit in September. Members can access our full comment submission in the resources section.

Timeline and Next Steps

The comment period closes 90 days from the NPRM publication date. PHMSA has indicated a final rule could be published within 18–24 months. Operators are advised to begin reviewing their coating specifications and qualification programs now to ensure readiness for compliance.

Polyurea is not just another coating — it is a chemically engineered material that has fundamentally changed the way pipeline operators think about asset protection. Born from the reaction between an isocyanate component and a synthetic resin blend, polyurea forms an elastomeric membrane that bonds tenaciously to steel, concrete, and virtually any properly prepared substrate.

The Chemistry That Makes It Work

When isocyanate reacts with an amine-terminated polyether or amine chain extender, the result is a urea linkage — giving polyurea its name and its extraordinary properties. Unlike polyurethane systems that require moisture to cure, pure polyurea systems are completely insensitive to humidity and temperature during the spray process, allowing application in conditions where other coatings would fail.

Key Performance Properties

• Tensile strength: 2,000–4,500 psi depending on formulation
• Elongation at break: 300–600%, allowing movement with the pipeline
• Shore A hardness: 60–95, tunable for specific applications
• Gel time: 3–5 seconds; walk-on time: <30 seconds
• Temperature resistance: –40°F to +250°F continuous service
• Chemical resistance: excellent against crude oil, refined products, brine, and hydrogen sulfide

Comparison With FBE and Epoxy

Fusion-bonded epoxy remains popular for new mainline pipe due to its thin film build and compatibility with directional drilling. However, polyurea surpasses FBE in field joint coating, rehabilitation, and any application requiring impact resistance or substrate movement tolerance. Our coating comparison guide breaks down the performance data across 12 key metrics.

Application Equipment and Technique

Proper application requires plural-component spray equipment operating at 2,000–3,000 psi with heated hoses maintaining 140–160°F. Plural-component systems from leading manufacturers keep the A and B components separated until they meet at the spray gun. Our certified applicator program provides hands-on training with industry-leading equipment.