Inspectioneering Journal

FRP Corrosion Barrier Inspection: Non-Destructive and Non-Intrusive Technique

By Geoff Clarkson, CEO and Founder at UTComp, Inc.. This article appears in the March/April 2020 issue of Inspectioneering Journal


The use of Fiber Reinforced Polymer (FRP) for vessels and piping in the chemical processing industry (CPI) started in the 1950s. As experience with the behavior of the material system grew, standards and codes were developed for design and construction that aligned with standards and codes for equipment made with metallic materials. Several features were incorporated to create reliable operation.

One of the design features that evolved to significantly improve the reliability of FRP equipment is to incorporate a corrosion-resistant barrier onto the surface of the FRP that is to be exposed to corrosive chemical conditions – usually the inner surface of pipes, tanks or process vessels. The purpose of the corrosion-resistant barrier (“Corrosion Barrier”) is to protect the FRP used for structural support (structural FRP) from damage by the operating environment.

When the use of corrosion barriers was introduced, many owner-operators determined that a key to FRP reliability was to properly maintain the corrosion barriers. The principle behind this is to monitor the condition of the corrosion barrier. This approach almost always requires an outage and confined space entry.

This article describes the construction of corrosion-resistant FRP and the practices used for inspecting corrosion barriers, starting from the original visual inspection, to microscopic evaluation of sections through cutouts, and then to an advanced ultrasonic method that yields good correlation to destructive analytic results. Advanced ultrasonic techniques provide additional results that can be directly related to an ASTM standard[1] that is used globally to provide quantitative performance of FRP in corrosion service.

FRP Construction

Fiber reinforced polymers are used in many corrosive applications because the polymers provide superior corrosion protection to many metal alloys and they also protect the fiber reinforcements that provide structural properties. The surfaces and areas of FRP that will be exposed to corrosive service conditions are covered with a corrosion-resistant barrier.

The corrosion-resistant barrier is normally composed of layers of reinforced thermosetting polymer or a thermoplastic sheet. A thermosetting polymer is a polymer that is applied in liquid form with curing agents added that react with the polymer to form bonds between the polymer chains, known as cross-linking. Examples of thermosetting polymers include epoxy, vinyl ester, and polyester resins. A thermoplastic polymer is a polymer that can be deformed by some combination of heat and stress. Example thermoplastic materials include: polypropylene; polyvinyl chloride; polyethylene; polyvinylidene fluoride; and many others. Figure 1 shows typical configurations.

This content is available to registered users and subscribers

Register today to unlock this article for free.

Create your free account and get access to:

  • Unlock one premium article of your choosing per month
  • Exclusive online content, videos, and downloads
  • Insightful and actionable webinars
Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.

Comments and Discussion

Posted by Jabran Younas on June 1, 2020
What type of UT probe and what sound velocity is... Log in or register to read the rest of this comment.

Posted by Shubhadeep Sarkar on June 1, 2020
Very good article Sir. Log in or register to read the rest of this comment.

Posted by Gopal Sankar on June 2, 2020
Can we use it for assessing composite wrap... Log in or register to read the rest of this comment.

Posted by Geoff Clarkson on June 2, 2020
Thanks for your comments. Answers here: FRP can... Log in or register to read the rest of this comment.

Posted by Gopal Sankar on June 2, 2020
Any service provider to assess the composite... Log in or register to read the rest of this comment.

Add a Comment

Please log in or register to participate in comments and discussions.

Inspectioneering Journal

Explore over 20 years of articles written by our team of subject matter experts.

Company Directory

Find relevant products, services, and technologies.

Job Postings

Discover job opportunities that match your skillset.

Case Studies

Learn from the experience of others in the industry.

Event Calendar

Find upcoming conferences, training sessions, online events, and more.

Industry News

Stay up-to-date with the latest inspection and asset integrity management news.


Read short articles and insights authored by industry experts.


Commonly used asset integrity management and inspection acronyms.


Downloadable eBooks, Asset Intelligence Reports, checklists, white papers, and more.


Watch educational and informative videos directly related to your profession.

Expert Interviews

Inspectioneering's archive of interviews with industry subject matter experts.