How to Measure Surface Profile After Blasting Using Testex Replica Tape

September 17, 2024 | In NDT

Introduction

After abrasive blasting, steel surfaces exhibit peaks and valleys known as the surface profile. Accurately measuring this profile is critical to ensure optimal coating adhesion and long-term corrosion protection. Since surface profile irregularities are random and non-uniform, a reliable measurement method is essential.

Testex Press-O-Film™ Replica Tape has become one of the most trusted tools for measuring surface profile in the field, due to its simplicity, compliance with international standards, and ability to produce physical replicas for analysis.

Why Measuring Surface Profile is Important

Steel surfaces must be roughened before applying protective coatings to promote mechanical bonding. An inadequate profile can lead to:

Poor adhesion.
Premature coating failure.
Increased maintenance costs.

Correct surface preparation, verified with accurate measurement, ensures coatings last longer and perform as intended. Standards like ASTM D4417 Method C and ISO 8503-5 specify acceptable methods, including the use of replica tape.

What is Testex Press-O-Film Replica Tape?

Testex Press-O-Film™ Replica Tape consists of a layer of compressible foam bonded to incompressible polyester film. When the tape is burnished onto a blasted surface, the foam deforms and captures a "reverse replica" of the surface topography.

Key Benefits:

Non-destructive testing (NDT).
Industry-standard compliance (ASTM D4417 Method C).
Physical replica for visual documentation.
Ideal for field and lab use.

Available in various grades, replica tape is compatible with Testex Micrometer and DeFelsko PosiTector RTR series for precise profile height measurement.

Testex Replica Tape Grades Explained

To ensure accurate readings, choose the right grade of tape based on the expected profile range:

1. Conventional Testex Press-O-Film Tape Grades

Testex Press-O-Film replica tape is available in a variety of thickness ranges for measuring substrate roughness from 0.5 - 6 mils (12 - 150 µm).

Grade	Range	Measurement Tool
Coarse	0.8 - 2.0 mils (20 - 50 µm)	Testex Digital Micrometer Testex Analog Micrometer PosiTector RTR H Replica Tape Reader
X-Coarse	1.5 - 4.5 mils (40 - 115 µm)
X-Coarse Plus	4.0 - 6.0 mils (100 - 150 µm)
Coarse Minus	0.5 - 1.0 mils (12 - 25 µm)

2. Optical Grade Testex Press-O-Film Tape Grades

Testex Press-O-Film Optical Grade replica tape, when used with PosiTector RTR 3D models, provides higher quality surface data files (.SDF) than conventional replica tape. Optical Grade Replica Tape is available in X-Coarse.

Grade	H Range	2D/3D Range	Measurement Tool
Optical Grade X-Coarse	1.5 - 4.5 mils (40 - 115 µm)	0.4 - 4.5 mils (10 - 115 µm)	PosiTector RTR 3D

3. Legacy Testex Press-O-Film Tape Grades

All tape grades are available in the legacy roll format. Instructions and Standards will continue to support both methods and burnishing tools.

Step-by-Step: How to Use Testex Press-O-Film Replica Tape

1. Surface Preparation

Use cleaning putty to remove dust or abrasive residue. This ensures the tape adheres cleanly to the metal surface.

2. Tape Application (Burnishing)

Select the correct replica tape grade.
Apply tape to the blasted surface.
Use a burnishing tool or rounded object to press and rub the tape for at least 30 seconds.
The foam layer conforms to the surface profile.

3. Measure

Option 1: Use a Testex Micrometer

Insert the tape into a Testex analog or digital micrometer:

Subtract the film thickness (typically 50 µm) to determine profile height.
Take 2–3 measurements and average them for accuracy.

Option 2: Use a PosiTector RTR Replica Tape Reader

Insert the burnished tape into the PosiTector RTR H or RTR 3D.
The device automatically measures and stores surface profile height.
RTR 3D also records advanced 2D/3D roughness parameters.

Advantages and Limitations of Replica Tape

Advantages

Portable and rugged.
Cost-effective.
Repeatable and easy to use.
Physical records for traceability.

Limitations

Grade range limitations (must choose correct tape).
Potential human error in burnishing technique.
Slight accuracy variation at extremes of each range.

Using multiple grades or switching to RTR 3D helps overcome these limitations for comprehensive analysis.

How Accurate is Testex Press-O-Film Replica Tape?

In 2024, a comprehensive study was performed to determine an accuracy statement for replica tape. That study determined the following accuracy and precision statements:

Replica Tape Grade	Precision	Accuracy
Coarse	±2 µm (± 0.1 mils)	±8 µm (± 0.3 mils)
X-Coarse	±6 µm (± 0.2 mils)	±8 µm (± 0.3 mils)
X-Coarse Plus	±8 µm (± 0.3 mils)	±10 µm (± 0.4 mils)

Compliance with International Standards

Testex Press-O-Film Replica Tape and associated micrometers comply with:

ASTM D4417 Method C
ISO 8503-5
SSPC PA 17

DeFelsko’s PosiTector RTR models meet or exceed these standards, offering traceable and auditable data outputs for QA/QC.

DeFelsko Distributor in Singapore

LFC PTE LTD is the authorized distributor of DeFelsko products in Singapore. Our expert team can assist you in selecting the appropriate replica tape solutions for your surface profile measurement.

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