Can Wintact WT-100A Ultrasonic Thickness Gauge Measure Through Paint? Malaysia

Can Wintact WT-100A Ultrasonic Thickness Gauge Measure Through Paint? Malaysia

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A common question from maintenance engineers and inspection personnel is:

“Can an ultrasonic thickness gauge measure steel without removing the paint?”

For users considering the Wintact WT-100A Ultrasonic Thickness Gauge, the answer requires some care.

Ultrasonic thickness measurement works by sending sound through the test material and measuring the returning ultrasonic signal. When a coating such as paint is present between the probe and the base metal, that coating can affect the measurement.

Therefore, users should not automatically assume that a conventional ultrasonic thickness reading represents only the metal thickness when measuring over paint.

Why Can Paint Affect the Reading?

Paint and steel have different acoustic properties.

When an ultrasonic signal travels through:

Probe → Paint/Coating → Steel → Back Wall

the coating becomes part of the ultrasonic path.

Depending on the instrument, coating, thickness and measurement method, this can affect the displayed result.

A reading that appears stable does not necessarily mean that the instrument has automatically excluded the paint thickness.

Does This Mean Paint Must Always Be Removed?

Not necessarily in every application, but the inspection procedure matters.

For routine or non-critical checks, users may first evaluate whether consistent measurements can be obtained.

For measurements where the actual remaining metal thickness is important, particularly for corrosion assessment, technicians should follow an appropriate procedure and understand the capability of the gauge being used.

If necessary, a small measurement location may need to be properly prepared to obtain a reliable base-material reading.

What Is the Difference Between Standard and Through-Coating Measurement?

Some specialised ultrasonic thickness gauges provide measurement techniques designed to reduce or eliminate the influence of coatings.

This is commonly associated with functions such as:

Echo-to-Echo measurement

Multiple-echo measurement

Through-coating measurement

These functions should not be assumed to exist on every ultrasonic thickness gauge.

If measuring metal through paint without removing the coating is a critical requirement, confirm that the selected instrument specifically supports the required measurement method.

Example: Corroded Painted Pipe

Imagine a maintenance technician needs to check the remaining wall thickness of a painted steel pipe.

The objective is not:

“What is the combined thickness of paint and steel?”

The actual question is:

“How much steel wall remains?”

If the coating influences the reading, the maintenance team may incorrectly interpret the condition of the pipe.

This is why correct measurement technique is important for corrosion monitoring.

Recommended Measurement Approach

For suitable applications, a basic workflow may include:

Identify the pipe or component.

Inspect the surface condition.

Determine whether a coating is present.

Confirm whether the instrument and procedure are suitable for measurement over that coating.

Prepare the measurement location if required.

Apply appropriate ultrasonic couplant.

Take several measurements.

Check for stable and repeatable readings.

Record the exact measurement location.

Compare with previous measurements where available.

What About Rust?

Paint is not the only surface condition that can affect ultrasonic measurements.

Other factors include:

Loose rust

Heavy corrosion

Scale

Dirt

Uneven surfaces

Pitting

Poor probe contact

For heavily corroded components, technicians may need to take multiple measurements around the area rather than relying on one reading.

Why Repeatability Matters

Suppose you measure the same location several times:

Reading 1: 7.62 mm

Reading 2: 7.61 mm

Reading 3: 7.63 mm

The results are relatively consistent.

Now consider:

Reading 1: 7.62 mm

Reading 2: 8.41 mm

Reading 3: 6.95 mm

The large variation suggests that the measurement conditions, surface, coupling, probe position or instrument settings should be investigated before recording a final result.

Can WT-100A Be Used for Corrosion Monitoring?

The WT-100A can be used to obtain thickness measurements on suitable materials and under appropriate measurement conditions.

Potential applications include:

Steel pipes

Storage tanks

Steel plates

Fabricated components

Industrial machinery

Selected pressure-containing components

For corrosion monitoring, however, the important objective is not simply obtaining a number.

A better approach is:

Measure → Record → Repeat at Same Location → Compare → Identify Trend

When Should You Consider a More Advanced Thickness Gauge?

A more specialised ultrasonic thickness gauge may be appropriate when the application requires:

Reliable measurement through coatings

Very thin material measurement

High-temperature measurement

Specialised probes

Advanced data logging

More demanding NDT procedures

Instrument selection should therefore be based on the application, not only on price.

FAQ: Can I Just Put WT-100A on a Painted Pipe and Read the Number?

You may obtain a reading, but you should not automatically assume that the displayed value represents the exact remaining steel wall thickness without understanding the effect of the coating and the measurement method.

For important corrosion or safety-related measurements, use an appropriate procedure.

Looking for an Ultrasonic Thickness Gauge in Malaysia?

MTM Precision supplies ultrasonic thickness gauges and other industrial testing instruments for Malaysian maintenance, engineering, fabrication and QA/QC applications.

Tell us:

What material are you measuring?

Is the surface painted or coated?

What is the approximate thickness?

What component are you inspecting?

MTM Precision can help you select a suitable thickness measurement solution for your application.

Contact MTM Precision

MTM Precision Sdn. Bhd.

Showroom & Service Centre

No. 29-1 & 29-2, Jalan Bandar 18,

Pusat Bandar Puchong,

47160 Puchong, Selangor, Malaysia