Pull-Off — ISO 4624 / ASTM D4541

What Is Pull-Off?

The pull-out test is where the standard pin (dolly) attached to the coating surface is pulled vertically at a constant speed; It is the test in which the stress at the moment of rupture and the type of rupture are determined.

Purpose of Pull-Off

The aim is to quantify the adhesion strength of the coating and reveal the weakest interface of the coating system.

Which Products Is Pull-Off Applied To?

Heavy duty industrial coatings
Concrete and steel structure coatings
Termal sprey kaplamalar
Zemin kaplama sistemleri

In Which Sectors Is Pull-Off Used?

AutomotiveMetalConstructionMachinery

Standards Related to Pull-Off

ISO 4624
ASTM D4541
ISO 16276-1
ASTM D7234 (on concrete)

Pull-Off Conditions

Pim: Standard diameter metal pin; surface sanded and cleaned
Glue: Higher strength than coating; curing period is observed
Tensile speed: Constant speed defined in the standard
Kopma tipi: Classified as A (substrate/coating), B (interlayer), Y (adhesive)

Equipment for Pull-Off

Pull-out (adhesion) tester
Standard pin set and adhesive
Coating-thickness gauge
Kesici halka (gerekiyorsa)

Sample Requirements for Pull-Off

The coating and adhesive must be fully cured.
Pin axis must be perpendicular to the surface
Measurement points must be representative and at sufficient distance from each other.
The number of specimens is defined in the standard

Duration of Pull-Off

Typically 2–4 days including adhesive cure.

Pull-Off Procedure

1The surface and pin are prepared.
2The pin is glued and the curing period is waited.
3If necessary, the coating is cut around the pin.
4The pin is pulled vertically at a defined speed.
5The failure stress is recorded.
6The type of rupture and surface percentage are evaluated.

Pull-Off Acceptance Criteria

The acceptance criterion is the minimum breaking strength given in the specification; The type of rupture is also evaluated.

Evaluation of Results

Breaking of the adhesive (type Y) will invalidate the result; It only indicates that the coating strength is at least this value. Pulling the pin obliquely reduces the result. On porous surfaces such as concrete, the rupture mostly occurs on the lower surface and this is not a coating defect.

Pull-Off Report

Standard applied
Coating system and thickness
Pin diameter and adhesive
Tensile speed
Breaking strength and breaking type

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

ISO 12944
Paint and coating specifications

Paint and Coating Testing — What Does This Testing Field Cover?

The section below describes the field that the Pull-Off test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Paint and coating testing measures the adhesion of a coating to the surface, its mechanical durability and its resistance to environmental effects. Because a coating is a thin layer, the results depend both on the material and on the QUALITY OF APPLICATION; the same paint gives an entirely different result over a different surface preparation.

This dual dependence is the most important knowledge in the field. A coating failure usually arises not from the paint itself but from the surface preparation: oil residue, insufficient roughening, an oxide layer or moisture. Coating tests therefore assess not only the product but also the process, and the results are used for process control.

COATING THICKNESS is a recurring variable in the field. Many durability results relate directly to thickness; a thin area becomes the starting point of corrosion. Thickness measurement is therefore reported routinely alongside the other tests and is usually taken at several points — thickness falls at edges and corners, especially on complex geometries.

Three approaches are used on the adhesion side, each giving different information. The tape test is fast and suitable for field use but is a coarse scale. The cross-cut test shows behaviour at the intersections of layers. The pull-off method produces a numerical strength value and is the most suitable for comparison.

On the mechanical side, flexibility (mandrel bending), impact resistance, hardness, abrasion and stone chip resistance are measured. Stone chipping has a special place in automotive: gravel striking the coating under real road conditions is simulated, and the result is assessed according to whether the coating continues to protect the base metal.

On the appearance side, gloss and colour difference are monitored NUMERICALLY. Colour is assessed with a colour measuring instrument rather than by eye and the colour difference is expressed as a number; this makes it possible to compare different lots and different suppliers.

On the durability side, accelerated ageing (xenon arc, fluorescent UV), humidity, condensation and salt spray are applied. The result is assessed with scales for blistering, rusting, creep from a scribe and loss of adhesion; these scales are defined in separate standards and the report must state which was used.

In industrial processes such as powder coating and electrophoretic coating, the curing cycle (temperature and time) is what determines the result. An under-cured coating looks good but has poor chemical resistance and adhesion; oven profile measurement is therefore part of coating quality control.

Method groups in this field

Thickness
Dry film thickness by magnetic and non-magnetic methods; multi-point measurement and assessment of the distribution.
Adhesion
Tape test, cross-cut test and pull-off adhesion strength.
Mechanical strength
Mandrel bend flexibility, rapid deformation (impact), pencil and scratch hardness, Taber abrasion, stone chipping.
Appearance
Gloss measurement, colour difference calculation, orange peel and surface defect assessment.
Environmental durability
Salt spray, humidity, condensation, xenon arc and fluorescent UV ageing, chemical and stain resistance.
Assessment scales
Scales for blistering, degree of rusting, creep from a scribe and loss of adhesion.

Commonly confused in this field

A coating result depends on the surface preparation; even if the paint itself is good, a poor preparation gives a poor result.
A durability result without a reported thickness cannot be compared.
The tape test is a coarse scale; numerical comparison requires the pull-off method.
Colour cannot be assessed by eye; numerical colour difference measurement is required.
An ageing result without a stated assessment scale cannot be interpreted.
If the curing cycle is incomplete the coating looks good but its durability is poor; the oven profile is part of quality control.

Which decisions these results support

Paint system approval and supplier selection
Process control of the paint line and lot acceptance
Supporting outdoor and automotive durability claims
Detecting defects arising from surface preparation
Monitoring colour and gloss consistency lot by lot

Related Tests

Frequently Asked Questions About Pull-Off

According to which standard is Pull-Off made?

Pull-Off is executed in scope ISO 4624, ASTM D4541, ISO 16276-1 and ASTM D7234 (on concrete). The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.

Which products does Pull-Off apply to?

Mainly applied to Heavy duty industrial coatings, Concrete and steel structure coatings, Termal sprey kaplamalar and Zemin kaplama sistemleri. Whether your product is included in the scope is determined by examining its technical specifications and intended use.

Under what conditions is Pull-Off done?

The determining parameters are: Pim — Standard diameter metal pin; surface sanded and cleaned, Glue — Higher strength than coating; curing period is observed and Tensile speed — Constant speed defined in the standard. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.

What kind of sample is needed for Pull-Off?

The coating and adhesive must be fully cured., Pin axis must be perpendicular to the surface and Measurement points must be representative and at sufficient distance from each other.. The number of samples is determined according to the product standard and the scope to be reported.

How long does Pull-Off take?

Typically 2–4 days including adhesive cure. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.

What is the Pull-Off result called "appropriate"?

The acceptance criterion is the minimum breaking strength given in the specification; The type of rupture is also evaluated.