DFT Gauge for Structural Steel, Tank & Pipeline Coating Inspection Malaysia
Protective coatings are widely used on structural steel, tanks and pipelines to help protect metal surfaces from corrosion and environmental exposure.
But applying paint is not enough.
For coating quality control, contractors and inspectors may also need to check DFT – Dry Film Thickness after the coating has dried or cured.
A portable DFT gauge or coating thickness gauge allows suitable coatings over compatible metal substrates to be measured non-destructively.
For general industrial Fe/NFe coating measurement, the TASI TA521A and TA522A Coating Thickness Gauges provide a measurement range of 0–2000 μm, Fe/NFe capability, automatic substrate recognition and Fe+Zn measurement capability.
For regular professional inspection, we generally prefer the TASI TA522A because it also provides manual measurement mode selection.
Why Is DFT Important for Protective Coatings?
Industrial coating systems may be designed to provide:
Corrosion protection
Weather resistance
Chemical resistance
Surface durability
Environmental protection
Longer service life
The required coating system may consist of several coats.
For example:
Steel → Primer → Intermediate Coat → Topcoat
After the coating system has dried or cured, DFT measurement can help determine whether the finished coating thickness meets the applicable specification.
Where Is DFT Inspection Used?
Potential applications include:
Structural steel
Steel tanks
Storage tanks
Industrial pipelines
Steel platforms
Machinery
Factory structures
Steel frames
Handrails
Equipment supports
Fabricated steel
Maintenance repainting
The exact inspection requirements depend on the project, coating system and applicable specification.
DFT Gauge for Structural Steel
Structural steel is one of the most common applications for magnetic coating thickness measurement.
A typical structure is:
Protective Coating → Steel
Because steel is ferrous, a suitable coating thickness gauge uses the magnetic induction principle.
Possible applications include:
Steel beams
Columns
Trusses
Platforms
Staircases
Handrails
Support structures
Fabricated frames
Measurements can be taken at specified locations and compared with the project's required DFT.
DFT Gauge for Storage Tanks
Industrial storage tanks often rely on protective coatings as part of their corrosion-control system.
Depending on the tank and project, coatings may be applied to external or internal surfaces.
DFT measurement may form part of:
New construction QC
Fabrication inspection
Painting contractor QC
Maintenance inspection
Recoating work
Project handover
The inspection procedure should define where and how measurements are taken.
DFT Gauge for Pipelines
Coated steel pipelines are another potential application.
The measurement objective may be to determine the thickness of a suitable protective coating over the pipe surface.
However, it is important to distinguish two completely different measurements:
Protective coating thickness → DFT / Coating Thickness Gauge
Remaining steel pipe wall thickness → Ultrasonic Thickness Gauge
These instruments are not interchangeable.
If corrosion has reduced the steel wall and you need to know the remaining wall thickness, a conventional DFT gauge is not the correct tool for that measurement.
TASI TA522A for Industrial Coating Inspection
The TASI TA522A provides:
General measuring range: 0–2000 μm
Stated accuracy: ±(3% + 1 μm)
Resolution below 100 μm: 0.1 μm
Fe magnetic induction measurement
NFe eddy current measurement
Automatic substrate recognition
Manual measurement mode selection
Fe+Zn measurement capability
Fe+Zn range: 3–500 μm
Zero calibration
μm / mm / mil units
2 readings per second
180° screen rotation
These features make it relevant to many general industrial coating QC applications within its specifications.
Why Manual Fe Mode Can Be Useful on Steel Projects
A structural steel project may involve hundreds or thousands of measurements on known steel substrates.
The inspector already knows:
Substrate = Ferrous Steel
Automatic recognition remains useful, but the TA522A's manual measurement mode gives professional users additional operating control during repetitive inspection.
This is one reason we position:
TA521A → General measurement
TA522A → Regular professional QC / inspection
Their stated core accuracy remains the same.
Before Starting DFT Inspection
Before measuring, review the project documentation.
You may need to know:
Coating system
Required DFT
Minimum thickness
Maximum thickness
Measurement locations
Number of readings
Acceptance criteria
Applicable standard
Calibration requirements
Reporting requirements
A coating thickness gauge only provides measurement data.
The applicable specification determines whether the coating is acceptable.
Why One Reading Is Not Enough
Consider a large steel tank.
Coating thickness may vary between:
Shell plates
Weld areas
Edges
Corners
Difficult-access locations
Different coating passes
One reading cannot represent the entire tank.
Likewise, one reading on a steel beam cannot necessarily represent the entire structural member.
For professional inspection, follow the required measurement procedure and sampling plan.
DFT Inspection Workflow
A practical coating inspection process may look like:
Surface Preparation
↓
Coating Application
↓
Drying / Curing
↓
Contractor Internal DFT Check
↓
Corrective Action if Required
↓
Final DFT Inspection
↓
Documentation
↓
Project Handover
Internal measurement before final inspection can help identify issues earlier.
What Should Be Recorded?
Depending on project requirements, DFT inspection records may include:
Project name
Structure/component ID
Area or location
Coating system
Required DFT
Individual readings
Date
Operator/inspector
Instrument identification
Calibration status
Acceptance result
Remarks
Good documentation makes the measurement data much more useful.
Coating Thickness vs Corrosion Thickness
This distinction is especially important in tanks and pipelines.
Suppose you have:
Paint → Steel Tank Wall
Two inspections may be required.
Coating Inspection
Question:
How thick is the protective coating?
Instrument:
DFT / Coating Thickness Gauge
Corrosion / Remaining Wall Inspection
Question:
How much steel wall remains?
Instrument:
Ultrasonic Thickness Gauge
For industrial maintenance teams, these two instruments can complement each other.
Can TA522A Measure Through Paint to Check Steel Wall Thickness?
Do not treat the TA522A as an ultrasonic wall thickness gauge.
Its purpose is coating thickness measurement.
If you need to determine the remaining thickness of a steel tank or pipeline due to corrosion, discuss an appropriate ultrasonic thickness gauge instead.
What About Galvanized Structures?
Some structures use galvanized steel.
A simplified layer structure is:
Steel → Zinc
If additional paint is applied:
Steel → Zinc → Paint
The TASI TA521A and TA522A provide Fe+Zn capability, with a specified Fe+Zn measurement range of 3–500 μm.
However, multilayer systems require careful interpretation.
Always identify which thickness needs to be measured before selecting the measurement method.
What About Aluminium Tanks or Components?
For suitable coatings over compatible conductive aluminium, the TA522A supports NFe eddy current measurement.
This gives it broader application coverage than an Fe-only DFT gauge.
However, substrate, coating and geometry should always be checked before measurement.
Curved Pipeline Surfaces
Pipelines introduce another consideration: curvature.
A pipe is not a flat steel plate.
Measurement conditions may be influenced by:
Pipe diameter
Surface curvature
Probe geometry
Measurement position
If pipe coating inspection is a critical application, confirm the instrument's suitability for the actual pipe geometry and follow the relevant measurement procedure.
Calibration for Project Inspection
Project work may require current calibration documentation for the measurement instrument.
Before arriving at site, check whether the client, consultant or inspection procedure requires:
Calibration certificate
Specific calibration interval
Instrument identification
Verification checks
Traceability
Particular gauge specifications
Do not wait until project handover to discover that the instrument documentation does not meet the requirement.
Who Uses DFT Gauges?
Potential users include:
Painting contractors
Protective coating contractors
Steel fabricators
Tank manufacturers
Pipeline contractors
Oil & gas maintenance teams
Factory maintenance teams
Engineering contractors
QA/QC personnel
Coating inspectors
Third-party inspection companies
For these users, a portable coating thickness gauge can become an important part of routine coating QC.
Common DFT Inspection Mistakes
Confusing DFT With Steel Wall Thickness
Use the correct instrument for each measurement.
Taking Only One Reading
Large structures normally require multiple measurements according to the applicable procedure.
Ignoring Calibration Requirements
Project inspection may require valid instrument documentation.
Measuring Without Knowing the Required DFT
A thickness reading must be compared against an acceptance requirement.
Ignoring Pipe Curvature
Curved surfaces require additional consideration.
Assuming Every DFT Gauge Meets Every Project Standard
Always check the actual project specification before purchasing.
FAQ
What does DFT mean?
DFT means Dry Film Thickness.
What gauge is used to measure paint thickness on structural steel?
A suitable magnetic induction coating thickness gauge can be used for compatible coatings over ferrous steel.
Can TASI TA522A measure protective coating on steel?
Yes, for suitable coatings over compatible ferrous steel within its measurement specifications.
What is the TA522A measurement range?
The specified general measurement range is 0–2000 μm.
Can TA522A measure tank wall thickness?
It is a coating thickness gauge, not a conventional ultrasonic gauge for measuring steel tank wall thickness.
What gauge is used for remaining pipe wall thickness?
An appropriate ultrasonic thickness gauge is commonly used for remaining wall thickness inspection.
Can TA522A measure coating on aluminium?
Yes, for suitable coatings over compatible conductive non-ferrous substrates using eddy current measurement.
Is TA522A better than TA521A for project inspection?
Both have similar core measurement specifications. For repetitive professional inspection, we generally prefer TA522A because it adds manual measurement mode selection.
Looking for a DFT Gauge for Structural Steel, Tanks or Pipelines in Malaysia?
Tell MTM Precision exactly what you need to inspect:
Structural steel coating?
Tank protective coating?
Pipeline coating?
Remaining steel wall thickness?
Galvanized steel?
We can help identify whether you need a coating thickness gauge, DFT gauge or ultrasonic thickness gauge.
For general portable Fe/NFe coating inspection, the TASI TA521A and TA522A can be considered according to the application and project requirements.
Contact MTM Precision
MTM Precision Sdn Bhd
No. 29-1 & 29-2, Jalan Bandar 18
Pusat Bandar Puchong
47160 Puchong, Selangor, Malaysia
Website: www.mtmpre.com.my
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
26 Aug 2026
