MEK Rub | EUROLAB

What Is MEK Rub?

MEK rubbing test, in which the coating surface with a cloth impregnated with methyl ethyl ketone is rubbed back and forth at a defined pressure; It is the test in which the number of double rubbings required to wear the coating down to the lower surface or the degree of damage after a defined number of rubbings is determined.

Purpose of MEK Rub

The purpose is to quickly check whether the coating has cured sufficiently.

Which Products Is MEK Rub Applied To?

Toz kaplamalar
Two-component industrial paints
Pipe and tank inner coatings
Sahada uygulanan kaplamalar

In Which Sectors Is MEK Rub Used?

AutomotiveMetalConstructionMachinery

Standards Related to MEK Rub

ASTM D5402
ASTM D4752
ISO 2812-3 (related method)

MEK Rub Conditions

Solvent: Metil etil keton (MEK)
Rubbing: Back and forth movement at defined pressure; One round trip counts as one double rub
criterion: Subsurface exposure or ASTM D4752 rating (0–5)
Bez: Cloth and impregnation amount defined in the standard

Equipment for MEK Rub

MEK rub test setup or hand application
Standard cloth and MEK
Coating-thickness gauge
Fume hood

Sample Requirements for MEK Rub

Coating curing time must be completed
Coating thickness must be measured
The cloth should be kept sufficiently wet throughout rubbing.
Measurement points must be representative

Duration of MEK Rub

Typically 1 day.

MEK Rub Procedure

1Coating thickness is measured.
2The cloth is wetted with MEK.
3Double rubbings are applied at defined pressure.
4The surface is examined at regular intervals.
5It continues until the bottom surface appears or until the defined number of times.
6The result is reported as the number of double rubs or degrees.

MEK Rub Acceptance Criteria

The acceptance criterion is the minimum number of double rubs or the maximum degree of damage given in the specification.

Evaluation of Results

The method indirectly measures the degree of cure; thick coatings give higher rub numbers than thin coatings, so comparison cannot be made without reporting thickness. MEK is flammable and harmful, it should be worked in a fume hood.

MEK Rub Report

Standard applied
Coating system and thickness
Curing time and conditions
Number of double frictions or degrees
Visual findings

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

Pipe and tank coating specifications

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

The section below describes the field that the MEK Rub 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 MEK Rub

Does the MEK rubbing test accurately measure the degree of cure?

It is an indirect indicator. Insufficiently cured coatings wear prematurely, but the result also depends on the coating thickness and type. For the exact degree of cure, methods such as DSC and residual exotherm measurement are used.