Pulsed Eddy Current (PEC): An In-Depth Guide [New for 2025]

Pulsed eddy current testing is an advanced non-destructive testing (NDT) method used to detect corrosion and measure wall thickness in ferromagnetic materials—without removing insulation.

It works by emitting a short, controlled pulse of electromagnetic energy into a material and analyzing the resulting eddy current response.

Unlike conventional eddy current inspection, which typically requires direct contact and bare metal surfaces, pulsed eddy current testing can be performed through non-conductive layers like paint, fireproofing, or insulation. This makes it especially valuable for inspecting assets such as pipelines, storage tanks, and pressure vessels in environments where surface access is limited or removal of insulation is impractical.

Because it is fast, repeatable, and non-intrusive, pulsed eddy current testing is widely used in the oil and gas, chemical, power, and maritime industries to reduce downtime, improve safety, and extend asset life.

How Pulsed Eddy Current Inspection Works

Pulsed eddy current inspection is based on the generation and measurement of electromagnetic responses in conductive materials.

A probe emits a short, high-energy pulse of electromagnetic energy into the material. This pulse induces eddy currents below the surface, which decay over time.

The decay rate is influenced by the thickness of the material. By measuring this decay, inspectors can identify areas of metal loss, corrosion, or thinning—without needing to remove coatings or insulation.

Key Components of a Pulsed Eddy Current System

• PEC unit: The central processing device that powers the probe, collects data, and performs signal analysis.
• Probe: Emits the pulse and detects the electromagnetic response.
• Display and software: Used to visualize signal decay curves and calculate material thickness.

Wall Thickness Measurement Through Insulation

One of the major advantages of pulsed eddy current inspection is its ability to measure wall thickness through non-conductive layers.

The technology can inspect through coatings, fireproofing, and insulation up to several centimeters thick, making it ideal for applications where surface access is restricted or insulation removal would be costly.

Using Drones for Pulsed Eddy Current Inspections

At Voliro, we recently launched the first-ever drone-enabled pulsed eddy current instrument.

Called the Voliro PEC sensor, this new instrument brings advanced PEC technology to aerial inspections for the first time. Mounted to the Voliro T drone, the system enables inspectors to collect PEC data at height or in difficult to reach spaces—without putting personnel at risk or requiring costly temporary infrastructure.

Drone-based pulsed eddy current inspection is transforming how asset owners and service providers access hard-to-reach areas.

Traditionally, pulsed eddy current equipment required direct human access—often involving scaffolding, rope access, or elevated platforms. But with drone integration, those limitations are disappearing.

Why Drone-Based PEC Matters

• Access at height. Ideal for inspecting vertical assets like stacks, chimneys, towers, and flare systems.
• Safe and efficient. Eliminates the need for rope access or scaffolding, reducing risk and saving time on every inspection.
• Built for insulated assets. Performs accurate PEC measurements through insulation on elevated piping and structural elements.

This innovation extends the reach of pulsed eddy current inspection to areas that were previously inaccessible or cost-prohibitive. The Voliro PEC sensor integrates seamlessly with the company’s existing drone platform, ensuring stability, consistent sensor pressure, and accurate signal interpretation—all critical for successful PEC applications in the air.

Learn more about the Voliro PEC probe.

Where Pulsed Eddy Current Is Used

Pulsed eddy current testing is widely used in industries where corrosion monitoring and wall thickness measurements are needed, but direct access to the surface is limited.

Because pulsed eddy current inspection can be performed through insulation, coatings, and fireproofing, it is a practical alternative to traditional contact-based NDT methods in many field environments.

Common Industries

• Oil & Gas assets. Used offshore and in downstream facilities to inspect insulated piping, pressure vessels, and structural components where access is difficult.
• Chemical plants. Ideal for process piping systems with extensive insulation and fireproofing.
• Power plants. Enables inspection of boiler tubes, steam lines, and other critical assets without dismantling insulation.

Typical Applications

• Storage tanks. Inspect for corrosion under insulation on tank walls and roofs.
• Pipe racks. Evaluate wall loss in elevated or congested piping systems without scaffolding.
• Vessels with coatings or insulation. Detect internal corrosion without removing surface layers.

In all of these scenarios, pulsed eddy current testing helps reduce downtime and inspection costs while improving safety and data coverage.

Pulsed Eddy Current vs Eddy Current: What’s the Difference?

Both pulsed eddy current and traditional eddy current inspection are electromagnetic non-destructive testing (NDT) methods used to evaluate the condition of metal structures.

However, they differ significantly in how they operate and what they are best used for.

The biggest difference between the two is in accessibility. Pulsed eddy current is ideal when insulation or coatings cannot be removed, while eddy current inspection offers higher resolution for detecting small surface defects when direct access is available.

Here’s a comparison to clarify their strengths and limitations:

Criteria	Pulsed Eddy Current	Eddy Current Inspection
Flaw Detection	Best for subsurface flaws and wall loss	Best for surface and near-surface cracks
Surface Requirements	Can inspect through coatings and insulation	Requires bare, clean metal surface
Couplant Needed	No	No
Frequency Range	Low-frequency pulsed signals	High-frequency continuous waveforms
Best Use Cases	Corrosion under insulation, wall loss on insulated piping or tanks	Crack detection on uncoated tubing, weld inspection

Pulsed Eddy Current Equipment Overview

Pulsed eddy current equipment is made up of several integrated components that work together to perform reliable thickness measurements through insulation.

These tools are engineered for accuracy, portability, and use in demanding industrial environments.

Main Components

• PEC sensor or probe. Emits the electromagnetic pulse and detects the resulting decay signal from the test material.
• Pulse generator. Delivers a controlled, low-frequency pulse to the probe to initiate eddy current flow in the target material.
• Data processing unit. Interprets the received signal and converts it into meaningful thickness or corrosion data. Often this is the core of the Pec unit.
• Interpretation software. Displays signal decay curves, material thickness estimates, and corrosion profiles in a user-friendly format.

A typical PEC unit includes all of the above, often integrated into a ruggedized, field-ready system for use in complex inspection settings. Portable versions may be handheld or mounted to automated platforms, depending on access and scope of the inspection.

Drone-Mounted PEC Systems

One of the most innovative applications of pulsed eddy current equipment is integration with drones.

In this setup, the probe and processing unit are mounted to a UAV, allowing for pulsed eddy current inspection at height or in confined spaces—without scaffolding, rope access, or shutdowns.

This improves inspector safety and enables rapid data collection in areas that are traditionally difficult or dangerous to reach.

Pulsed Eddy Current Limitations

While pulsed eddy current is a valuable tool for non-destructive testing, it’s important to understand where its capabilities taper off. No single method fits every scenario, and PEC is no exception.

Here are some of the most common pulsed eddy current limitations to consider during inspection planning:

• Lower resolution than UT. PEC does not provide the same level of detail as ultrasonic testing when detecting fine cracks or pinpoint flaws.
• Limited use on small or complex geometries. PEC is not well suited for inspecting very small components or surfaces with sharp bends, edges, or high curvature.
• Not ideal for tight cracks or laminations. PEC is best at detecting general wall loss or large-scale corrosion; it is less effective at identifying tightly packed cracks or internal delaminations.

Pulsed Eddy Current Training: What Technicians Need to Know

Effective use of pulsed eddy current testing requires specialized training to ensure accurate data collection and interpretation.

Technicians must understand both the theoretical and practical aspects of the method to perform reliable inspections in the field.

What’s Included in Pulsed Eddy Current Training

• Basic electromagnetic theory. Understanding how eddy currents are generated and how signal decay relates to material condition.
• PEC equipment operation. Hands-on training with probes, Pec units, and software interfaces used during inspections.
• Signal analysis and interpretation. Learning how to identify wall loss, corrosion patterns, and distinguish true indications from noise.
• Industry certifications. Some industries may require PEC-specific endorsements or integration into broader NDT certification programs (e.g., ASNT, ISO).

Pulsed eddy current training ensures technicians are qualified to perform inspections with confidence—maximizing the technology’s potential while minimizing errors in the field.