Powder coating thickness must be reported with its unit, measurement stage and acceptance rule. For an aluminum part, agree the cured-film requirement, suitable measuring method and locations before production. A bare number such as “80” leaves the receiving team guessing.
This guide helps buyers compare thickness reports for coated rails, frames and housings. Start with the finish specification, then check whether the supplied result answers that requirement.
On this page
Specify the powder coating thickness stage first
DeFelsko’s powder-thickness guide distinguishes measurements before and after cure. Dry film thickness, commonly abbreviated DFT, describes the cured film. Applied powder height and a prediction of cured thickness are different report entries.
The guide explains that powder generally reduces in thickness during curing. Do not use one universal reduction percentage to turn an uncured reading into a finished-film result. Ask what the instrument reports and how any prediction is established for the actual system.
Put the required stage beside the value on the purchase order. If an in-process prediction is supplied, retain it under that label. Request the final cured-film evidence required by the approved inspection plan.
Use the coating product documents and released project specification to establish the permitted range. This article does not assign a universal film thickness to every aluminum application or recommend an application setting.
Match the method to the aluminum part
DeFelsko describes electronic coating gauges that use magnetic principles on steel and eddy-current principles on other metals. The substrate, coating and available part geometry determine which instrument and probe are suitable.
For a coated aluminum rail, give the inspection team the section drawing and coating-system identity. Identify narrow faces, curved regions, edges and recesses where a proposed probe may need a suitability review.
Request the method designation, applicable edition, instrument and probe identity, and inspection procedure. A gauge used successfully on a broad flat panel should not automatically be treated as suitable for every corner of a small extrusion.
If the coating includes multiple layers or an existing surface treatment, ask what the proposed result represents. Does the procedure address the ordered layer, a combined system or another defined quantity? Resolve that question before comparing the number with a single-layer requirement.
A coating-thickness measurement and an eddy current discontinuity inspection answer different questions. Sharing a physical principle does not make their reports interchangeable.
Keep calibration, verification and adjustment separate
DeFelsko’s calibration terminology distinguishes three activities. Calibration is a controlled, documented comparison with traceable standards. Verification is the user’s accuracy check using known references. Adjustment aligns readings with a known sample for a particular surface or range.
The same resource identifies substrate shape, roughness, edge effects and temperature among factors that may require adjustment. Have the inspection owner define the appropriate checks for the actual gauge, probe and part condition.
Retain the calibration record and the relevant verification or adjustment information required by the inspection plan. Writing “calibrated” in a report does not explain which checks were performed on the supplied part geometry.
Do not create a universal recalibration interval from a supplier brochure. Use the instrument guidance and the organization’s approved quality process. Record the status that applied when the delivery was inspected.
For receiving review, ask whether the reference covers the expected thickness range and substrate. If a check raises a concern, retain the original results and have the inspection team determine what needs re-evaluation. Do not silently replace the record with a more favorable reading.
Make the measured locations visible
Mark the required faces and locations on the drawing or inspection map. Give each location an identifier that can travel from the coating order to the measurement record. A note saying “three readings” is incomplete if nobody can find those areas later.
Keep part identity, batch reference, drawing revision and coating product with the map. State whether the report concerns finished production parts or a separately prepared panel. If a panel represents an order, record the agreed relationship and its limits.
Ask the responsible team to define how many readings form a reported result and how acceptance is applied. A single reading, an average at one location and an average across different faces are different data summaries.
Keep the original location results available. If an area cannot be measured by the approved method, document the limitation and obtain the agreed alternative. Leaving the area out without explanation changes the inspection scope.
Read a fictional receiving report
Assume an invented order requires a cured film between 60 and 100 µm at each of three named locations, with both boundaries included. These limits are teaching inputs, not a coating recommendation or an actual inspection specification.
| Reported location | Comparison with the assumed range |
|---|---|
| A: 55 µm | Below the invented 60 µm lower limit. |
| B: 75 µm | Inside the invented numerical range. |
| C: 85 µm | Inside the invented numerical range. |
The average is approximately 71.67 µm. It lies inside the stated interval, but it does not satisfy the assumed rule that every named location must meet the limits. Preserve the location data when reporting the average.
Now consider a separate fictional result of 80 µm. It equals 0.080 mm or approximately 3.15 mils, using 25.4 µm per mil. The unit conversion changes the notation; it does not change the inspection stage or prove acceptance.
If that 80 µm value is an uncured prediction, it cannot simply be entered as a measured cured-film result. If the unit is missing, request it instead of assuming micrometers. A report needs the complete measurement statement.
Prepare the cutting and coating handoff
For the cutting order, define the supplied blank dimensions, cut quantities, end condition and current drawing. Identify the features that must remain recognizable through downstream finishing.
For the coating order, add the product reference, treatment boundaries, film requirement and final inspection scope. Keep dimensional fit and coating thickness in separate acceptance fields. Neither field should automatically close the other.
Our cutting before powder coating guide covers the process handoff. The coating adhesion guide addresses another finishing assessment. A thickness reading alone does not complete every finish requirement.
Send JiurunCut the profile drawing and cut list to discuss the cutting scope. Include downstream coating requirements that affect blank preparation, and keep coating-process approval with the appointed finisher and quality owner.
Quick buyer questions
Is one mil the same as one millimeter?
No. One mil is 0.001 inch, or 25.4 µm. Write the unit beside every thickness value.
Can an uncured reading prove final film thickness?
Keep a powder-height measurement or cured-film prediction under its correct label. Obtain the cured-stage evidence required by the approved inspection plan.
Does a passing average mean every location passes?
Only the agreed acceptance rule determines the comparison. In the fictional example above, a favorable average does not remove the low result at location A.
Does a thickness result prove adhesion or appearance?
Those requirements need their own agreed evaluation. Keep the thickness record connected to the order without expanding its scope.