Volumetric & Advanced NDT · C-SCAN
Corrosion Mapping
Thousands of thickness readings, one honest picture.
Corrosion mapping is encoded ultrasonic thickness surveying: an automated or manually-scanned probe takes thousands of wall-thickness readings across a defined area, each tied to its exact position, and renders them as a colour map. Instead of a handful of spot readings, the asset owner sees the corrosion — its extent, pattern and worst point — in one image.
The explainer
Watch how it works.
Schematic · loops automatically
1Define the grid
The inspection area is gridded and the encoded scanner referenced to it — every future reading will know its coordinates.
2Raster the surface
The probe sweeps line by line, pulsing thickness measurements every few millimetres of travel.
3Each echo becomes a pixel
Backwall arrival times convert to thickness; values paint the map — full wall in blue-green, thinning through amber into red.
4The morphology appears
Pits, grooves and general loss show as shaped features — the corrosion mechanism is often readable from the pattern alone.
5Baseline for next time
The dataset is archived; re-scanning later yields corrosion rates by location — evidence for remaining life and inspection intervals.
The physics
Each pixel of a corrosion map is a pulse-echo thickness measurement: sound in, backwall echo out, time converted to millimetres. The step change from conventional surveys is position encoding — the scanner records where every reading was taken, on a grid typically millimetres apart, producing full-coverage data instead of samples.
Coverage changes the statistics. Isolated pitting is precisely what sparse grid readings miss and full mapping catches; the C-scan presentation (plan-view colour map) makes the damage morphology obvious at a glance — general thinning, grooving, isolated pits — and the dataset yields minimum, mean and distribution rather than a single anxious number.
Mapped data is also a baseline. Repeat the scan next outage on the same grid and subtraction gives corrosion rate by location — the input every remaining-life and inspection-interval calculation actually wants. This is condition monitoring rather than spot-checking, and it is the standard of evidence modern integrity programmes expect on critical circuits.
Where it earns its keep
Typical applications
- Pressure vessel shells and heads at statutory examination
- Storage tank shells and suspect course mapping
- Pipework circuits flagged by CUI or process corrosion reviews
- Baseline-and-repeat condition monitoring on critical assets
Standards & schemes
| Designation | Covers |
|---|---|
| EN ISO 16809 context | Ultrasonic thickness measurement principles underlying each mapped reading |
| Client integrity procedures | Mapping grids, colour scales and reporting aligned to owner integrity programmes |
Corrosion mapping is delivered by UT-certified technicians with encoded-scanning competence; datasets are reported with minima, distributions and repeat-scan comparisons for integrity engineers.
Why map when spot thickness readings are cheaper?
Because pitting is spatially random and spot grids sample a tiny fraction of the surface — the worst pit is usually between the readings. Mapping buys certainty per square metre: the true minimum, the damage pattern, and a baseline that turns the next survey into a corrosion-rate measurement.
Can you map on live plant?
Yes — it is ultrasound from the outside, so operating vessels and lines are mapped routinely, subject to surface temperature and access. High-temperature techniques extend the envelope where insulation windows expose hot steel.
What do we get in the report?
Colour maps referenced to the asset grid, minimum and mean thickness per zone, pit depth callouts, comparison to nominal and retirement thickness, and — on repeat scans — corrosion rates by location. It is designed to drop straight into fitness-for-service and inspection-planning calculations.
Testing · Inspection · Certification
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