An evaluation of field-applied corrosion barriers

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According to an AMPP report, corrosion costs the global economy an estimated $2.5 trillion annually (3.4% of global GDP) and presents a significant challenge to refineries and petrochemical facilities. This article evaluates advanced field-applied corrosion protection technologies, providing a practical selection framework through comparative analysis and a Gulf Coast refinery case study.

Managing corrosion in changing refinery environments

The corrosion environment for many facilities has become significantly more challenging due to processing opportunity crudes with higher sulfur and acid content, extending run lengths between turnarounds, managing aging infrastructure beyond design parameters, adapting to biofuel processing and meeting stricter regulatory requirements.

These challenges require corrosion protection solutions that can be rapidly applied during limited turnaround windows, provide reliable protection in harsh environments and offer cost-effective alternatives to equipment replacement.

Understanding corrosion mechanisms

Effective protection technology selection requires an understanding of the primary corrosion mechanisms affecting mission-critical equipment. Refineries face multiple corrosion challenges, each requiring specific mitigation approaches. For example, Sulfidation occurs in high-temperature environments with sulfur compounds, particularly affecting crude distillation and coker units, where high flow rates can compromise protective iron sulfide scales. Another mechanism is naphthenic acid corrosion, which affects units processing high-TAN crude oils, causing rapid degradation of metal surfaces in atmospheric and vacuum distillation units.

Other significant mechanisms include chloride stress corrosion cracking, primarily affecting austenitic stainless steels in overhead systems and heat exchangers, and sour water corrosion resulting from condensation containing H₂S and acidic compounds. Each mechanism creates unique challenges that directly influence protection technology selection, as demonstrated in the case study presented in this article. Understanding these specific corrosion types and their behavior in different refinery environments forms the foundation for implementing effective, long-lasting protection strategies.

Three field-applied corrosion barrier technologies

Several field-applied corrosion protection technologies are available. Three solutions for comparative analysis will be analyzed. Each offers distinct advantages and limitations that must be evaluated against specific application requirements.

1. Weld overlay cladding

Weld overlay involves depositing a corrosion-resistant alloy onto base metal using various welding processes, creating a metallurgical bond between the cladding and substrate.

Common applications and considerations

Weld overlay is widely used for the internal surfaces of pressure vessels and reactors, nozzles and pipe connections, valve bodies and internals and field repairs of existing equipment. It is particularly suitable for restoring the pressure boundary and as a corrosion-resistant alloy.

2. High-velocity thermal spray (HVTS®) cladding

HVTS is an advanced technology that accelerates metallic particles to significantly higher velocities than conventional thermal spray methods. The process uses a specialized nozzle design and optimized gas dynamics to achieve velocities up to 1200 m/s. This results in denser, more adherent claddings with superior mechanical and corrosion resistance properties. Unlike other thermal spray processes, HVTS has the unique advantage of delivering shop-quality cladding properties in field applications, making it more adaptable than conventional wire spray processes for on-site corrosion protection.

HVTS technology is particularly suitable for:

  • Critical corrosion protection in aggressive environments and components requiring high-integrity, low-porosity cladding with superior erosion resistance
  • Complex geometries needing uniform coverage and in-situ applications where disassembly is impractical
  • Tight turnaround schedules where weld overlay is too time-consuming, while assuring corrosion resistance without post-weld heat treatment
  • Repair of existing internal cladding systems and repurposing assets for new operating environments (e.g., biofuel processing)

3. Organic epoxy coatings

For lower-temperature applications, organic epoxy coatings provide an alternative corrosion protection method involving high cross-link density epoxy novolac materials applied at ambient temperatures.

Common applications and considerations

Organic coatings can be applied by brush or airless spray with globally available contractors. Their low cost can make them attractive for newbuild vessel protection. The application requires strict environmental controls; temperature, moisture and contaminants affect cure time and adhesion. In service, these coatings have limited resistance to thermal cycling and shock.

Framework for selecting corrosion protection technologies

Several factors must be considered when selecting a corrosion mitigation technology for a specific application. First, proper characterization of the service environment is essential, as the operating temperature range, chemical composition of process fluids, presence of erosive particulates, flow characteristics and thermal cycling frequency all directly influence technology suitability. For instance, equipment operating below 140°C/284°F in non-erosive environments may be adequately protected by organic coatings at lower cost, while high-temperature applications (>500°C/932°F) typically require metallic protection systems like weld overlay or HVTS.

Application constraints are also considered, such as the available application window during turnarounds, substrate condition (welding is not recommended for thin or contaminated pressure boundaries), vessel access limitations, environmental control capabilities, equipment geometry complexity and post-weld heat treatment requirements. These practical factors often dictate technology selection beyond theoretical performance specifications.

Economic evaluation must look at the entire lifecycle rather than solely on initial application costs. This includes analyzing overall equipment lifecycle expenses, downtime costs during application, expected service life of the protection system, ongoing repair and maintenance requirements and risk-weighted costs of potential failure. Finally, inspection and quality control considerations vary by technology. While visual inspection is universal, specific methods like ultrasonic testing for weld overlay bond integrity, magnetic lift-off gauge and thickness testing for HVTS and organic coatings and holiday (spark) testing for organic coating systems are essential for ensuring system integrity throughout the operational lifecycle.

Case study

Flare knock out drum corrosion mitigation on U.S. Gulf Coast

Project overview

This case study examines a project at a Gulf Coast refinery where HVTS technology was applied to protect a flare knockout, demonstrating the practical application of the corrosion protection selection framework. The project addressed recurring coating failures and demonstrated certain advantages compared to conventional organic coating methods.

Refinery profile

  • Facility: Gulf Coast refinery
  • Capacity: 500,000 barrels per day
  • Established: Early 1900s
  • Project context: Part of the "Non-Road Diesel Project"

Challenge

The flare knockout drum, originally installed in 2011, experienced recurring failures of its protective organic coating. Applying the service environment characterization framework, the refinery identified that the failures were primarily attributed to:

  • Upset conditions during steam-outs (360°F / 182°C) causing thermal shock
  • Osmotic blistering of the organic coating
  • Short coating lifecycle (as little as two years)
  • Deep, localized pitting identified during inspection

Despite using Novolac epoxy with temperature and thermal shock resistance specifications, the organic coating system did not perform as expected in the long term under the operational conditions. This aligned with guidance that organic coatings often struggle in higher temperature applications with thermal cycling.

Solution selection process

The refinery maintenance team conducted a comprehensive analysis:

1. Service environment assessment

The recurring failures at temperatures up to 360°F (182°C) during steam-outs clearly exceeded the recommended temperature threshold (140°C/284°F) for organic coatings, indicating a metallic solution would be more appropriate.

2. Application constraints

With limited turnaround time available and the need for rapid return to service, the team evaluated both weld overlay and HVTS options, ultimately selecting HVTS technology due to its faster application speed and elimination of cure time requirements.

3. Economic evaluation

A lifecycle cost analysis revealed that while HVTS had a higher initial cost than reapplying organic coatings, the elimination of frequent recoating and associated downtime provided long-term economic benefits.

4. Inspection considerations

The team confirmed that appropriate quality control methods for HVTS application were available, including thickness testing and visual inspection protocols.

Implementation

The repair process included:

  1. Weld metal build-up in deeper pitted areas
  2. Abrasive blasting to achieve a 4-5 mil surface profile and white metal finish
  3. Application of HVTS cladding to approximately 235 ft² (22 m²) of surface area

Project details

The project implementation included:

  • Mobilization on short notice before winter holidays
  • Execution timeline of 3 days
  • No cure time required (compared to 3-10 days typically needed for organic coatings)
  • Application covered both top and bottom areas of the drum

Results

The implementation of HVTS technology delivered immediate benefits to the refinery operations. The rapid application process and absence of cure time requirements enabled the maintenance team to maintain their critical turnaround schedule without delays. This quick execution allowed the knockout drum to return to service promptly, minimizing operational downtime.

Maintenance requirements have been substantially reduced in the long term, eliminating the frequent attention previously needed with organic coating systems. The HVTS application extends asset protection throughout the remainder of the drum's expected service life, effectively addressing the concerns about premature coating failure that had been a recurring issue. This approach has eliminated the need for regular re-coating interventions, resulting in more consistent operation and reduced maintenance costs over time.

Comparative analysis of protection technologies

This comparison reveals why HVTS emerged as the optimal solution for the Gulf Coast refinery. It combines excellent corrosion protection with rapid application and minimal operational disruption.

Strategic corrosion management for modern refineries

Understanding the process environment, applying a structured framework (environment, constraints, economics, inspection) and considering the total cost of ownership are key to choosing the most effective corrosion mitigation solution for your unique scenario. The technologies and framework discussed here represent essential tools for maintaining operational excellence while managing asset integrity costs.

For more information, visit integratedglobal.com.

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