How Many Coating Thickness Measurements Should You Take on a Metal Part Malaysia
How Many Coating Thickness Measurements Should You Take on a Metal Part Malaysia
Content
When checking paint or powder coating thickness, is one measurement enough?
Usually, one reading provides information about only one small location. It may not represent the coating condition across the entire component.
For factory QA/QC, metal fabrication, automotive inspection and maintenance applications, a better approach is to take multiple measurements at defined locations and compare the results against the applicable specification.
A portable coating thickness gauge such as the UNI-T UT343A can support this type of routine inspection on compatible Fe and NFe metal substrates.
Why One Reading Can Be Misleading
Imagine measuring a powder-coated metal panel once:
Reading: 92 μm
That tells you the coating thickness at that particular measurement point.
It does not tell you whether another section measures:
90 μm
or:
190 μm
If coating uniformity matters, several representative locations should be checked.
Is There a Universal Number of Measurements?
No single number is correct for every application.
The appropriate number of readings depends on factors such as:
Component size
Component shape
Coating specification
Customer requirements
Inspection procedure
Relevant standard
Production process
Required confidence level
If a project, customer or inspection standard specifies a measurement procedure, follow that requirement.
Do not replace a defined standard with an arbitrary number of readings.
A Practical Approach for Routine Checks
For general process monitoring where no specific measurement procedure has been prescribed, users can establish consistent inspection locations.
For example, on a rectangular metal panel:
Top Left | Top Right | Centre | Bottom Left | Bottom Right
This provides a more representative picture than measuring only the centre.
The important principle is consistency.
If every production batch is checked at different random locations, comparing results over time becomes more difficult.
Example: Powder-Coated Cabinet Door
A QA inspector measures five defined locations:
Top Left: 91 μm
Top Right: 94 μm
Centre: 93 μm
Bottom Left: 90 μm
Bottom Right: 92 μm
These results appear relatively consistent.
Now consider:
Top Left: 91 μm
Top Right: 94 μm
Centre: 92 μm
Bottom Left: 89 μm
Bottom Right: 181 μm
The bottom-right area should be rechecked and investigated.
Without multiple measurements, this variation could easily be missed.
Large Components Need More Representative Coverage
For a large fabricated component, five readings may not provide sufficient coverage.
Instead, divide the surface into inspection zones.
For example:
Zone A – Upper Section
Zone B – Middle Section
Zone C – Lower Section
Then take defined measurements within each zone.
This helps determine whether coating variation is concentrated in a particular part of the component.
Small Parts Require a Different Approach
Small components present another challenge.
The available flat measurement area may be limited, and measurements near:
Edges
Corners
Tight curves
Small-radius surfaces
may be affected by geometry.
Before measuring very small parts, confirm that the component geometry is suitable for the coating thickness gauge and follow the manufacturer's measurement guidance.
Why Measurement Location Should Be Recorded
Suppose a QA report contains:
102 μm | 98 μm | 105 μm | 165 μm
Without knowing where those measurements were taken, troubleshooting becomes harder.
A better record might state:
Front: 102 μm
Left: 98 μm
Right: 105 μm
Rear: 165 μm
Now the production team knows exactly where to investigate.
For repeated factory inspection, defining measurement locations can make the data much more useful.
Minimum, Maximum and Average
When multiple measurements are taken, three values become particularly useful:
MIN – Minimum
Helps identify the thinnest measured area.
MAX – Maximum
Helps identify the thickest measured area.
AVG – Average
Provides an overall summary of the measurement group.
The UNI-T UT343A provides MAX, MIN and AVG functions, making it useful for multi-point coating checks.
However, do not use the average alone.
A very high or low individual reading can still matter even when the overall average appears acceptable.
Example: Why Average Alone Is Not Enough
Consider:
100 | 102 | 99 | 101 | 103 μm
The readings are closely grouped.
Now compare:
80 | 82 | 81 | 79 | 178 μm
An average cannot fully communicate the unusual fifth measurement.
For QA/QC, review the:
individual readings + MIN + MAX + AVG + measurement locations.
Automotive Paint Inspection
The same principle applies when checking vehicle paint.
Do not measure only one location on one door.
Instead, compare multiple metal panels and several suitable locations where necessary.
For example:
Bonnet → Roof → Front Door → Rear Door → Fender → Quarter Panel
If one panel produces significantly different readings, investigate it further.
Paint thickness measurement should be used as part of the inspection process rather than as automatic proof of a vehicle's repair history.
Incoming Inspection
Multiple measurements are also useful when receiving coated components from a supplier.
For example:
Purchase Order: 500 powder-coated brackets
Instead of visually inspecting the shipment only, the QA department can select samples according to its inspection plan and measure predefined points.
The results can then be compared against the agreed coating specification.
This gives the purchasing team objective data if a quality issue needs to be discussed with the supplier.
Production Trending
Consistent measurement locations also make long-term production data more valuable.
For example, if the same area gradually changes:
Week 1: 92 μm
Week 2: 95 μm
Week 3: 108 μm
Week 4: 125 μm
the factory may investigate the coating process before the variation becomes more significant.
This turns a coating thickness gauge from a simple spot-checking tool into part of a preventive QA/QC process.
UNI-T UT343A for Multi-Point Inspection
The UNI-T UT343A provides:
0–1750 μm measuring range
Fe/NFe substrate support
Automatic substrate recognition
Single measurement
Continuous measurement
MAX/MIN/AVG
199-reading storage
μm/mil selection
Upper and lower limit settings
These functions can support routine multi-point inspection in:
Powder coating | Metal fabrication | Manufacturing | Automotive | Maintenance | QA/QC
How Many Measurements Should Your Factory Take?
Instead of asking only:
"Should I take 3, 5 or 10 readings?"
start with:
What does the specification require?
How large is the component?
Which areas are most important?
Are there edges, curves or difficult geometries?
Are you performing a spot check or formal acceptance inspection?
Then establish a repeatable measurement plan.
Coating Thickness Measurement Malaysia
If your factory is setting up a coating inspection process, send MTM Precision details of your application:
Product + Coating + Substrate + Approximate Thickness + Inspection Purpose
For example:
"Powder-coated steel electrical enclosure, approximately 80–120 μm, final QA inspection."
We can help determine whether the UNI-T UT343A Coating Thickness Gauge is suitable for the measurement application.
MTM Precision Sdn Bhd
Showroom & Service Centre: Puchong, Selangor, Malaysia
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my
Serving customers throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kedah, Kelantan, Terengganu, Perlis, Sabah and Sarawak.
22 Sep 2026
