Electromagnetic Acoustic Transducer (EMAT) technology generates ultrasonic waves directly within the material using electromagnetic induction — without requiring liquid couplant contact with the inspection surface. This fundamental difference from conventional piezoelectric UT makes EMAT the appropriate corrosion mapping technology for applications where couplant application is impractical, where surface condition precludes consistent conventional UT coupling, or where the inspection must be performed at elevated temperatures that would compromise standard transducer performance.
EMAT probes use a combination of a static magnetic field and a
time-varying electromagnetic coil to induce Lorentz forces and magnetostriction
effects within the material surface — generating ultrasonic waves without
physical liquid contact. The probe does not need to touch the surface through a
couplant layer. Near-contact or lift-off inspection is possible, enabling
measurement through mill scale, surface coatings, and at elevated temperatures.
EMAT probes can operate at elevated surface temperatures — typically up
to 300–500°C depending on the probe configuration — enabling in-service
corrosion mapping on assets that cannot be cooled to ambient temperature for
conventional UT inspection. When mounted on a robotic arm with appropriate
high-temperature materials, EMAT enables continuous coverage thickness mapping
at operating temperatures without shutdown.
In environments where consistent couplant application is impractical —
rough surfaces, vertical surfaces, overhead positions, or surfaces with complex
geometry — EMAT's couplant-free operation eliminates the coupling variability
that degrades conventional UT data quality. Every measurement in the robotic
arm scan path is acquired under the same electromagnetic coupling conditions,
regardless of surface orientation.
EMAT naturally generates shear horizontal waves — a wave mode that
conventional piezoelectric transducers cannot efficiently produce. SH waves are
particularly effective for corrosion mapping in coated materials and at
elevated temperatures, where their mode characteristics provide coupling
advantages over conventional shear vertical or longitudinal wave
configurations.
EMAT Lamb wave generation enables rapid
area screening of thin-wall components — plates, thin-wall piping, and
structural panels — from a single scan line, with sensitivity to wall loss
extending laterally from the probe path. This enables faster area coverage than
point-measurement approaches on thin-wall inspection targets.
•
In-service corrosion mapping at elevated surface
temperatures (up to 500°C)
•
Corrosion mapping on coated and painted surfaces
without coating removal
•
Vertical
and overhead surface corrosion mapping without couplant management
•
Thin-wall plate and panel rapid corrosion screening
•
Refinery fired heater tube wall mapping during hot
standby
•
Structural steelwork corrosion mapping in difficult
surface condition environments
•
Pre-
and post-insulation removal CUI corrosion characterisation
EMAT corrosion mapping reports mirror the
format of conventional UT corrosion mapping outputs — 2D C-scan thickness maps,
3D thickness models, minimum wall identification, and area statistics — with
the addition of probe lift-off data and temperature logging where
high-temperature deployment conditions are relevant to data interpretation.