Mar resistance tester – SAMAR536

The Mar resistance tester is designed to evaluate the surface behaviour of paints, enamels and coatings when subjected to controlled mechanical action. The test makes it possible to verify if a  coating can withstand visible marks, surface alterations or damage caused by the sliding action of a curved, loop-shaped stylus.

The Mar resistance test is particularly suitable where the appearance of the finish is an important coating requirement. A surface may retain its functional integrity while still showing visible marring as a result of contact, rubbing or stresses occurring during handling, assembly or use.

The operating principle of the SAMAR536 consists of moving the coated sample beneath a loop-shaped stylus positioned at 45°, while applying the load specified by the test procedure. By progressively increasing the applied load, it is possible to determine the point at which the surface film begins to show the visible damage defined by the selected method.

Unlike tests that are focused on coating penetration or localised failure, the Mar test is focused on the resistance of the finish to visible surface marks. It is therefore useful for inspecting coatings and painted surfaces where preservation of appearance must be assessed together with coating performance.

The Mar resistance tester can be used on paints, protective finishes, enamels and organic coatings applied to samples that are compatible with correct test procedure. It is suitable both for laboratories and quality-control inspections, where the surface behaviour of samples manufactured with different formulations, application processes or drying conditions must be compared.

Being able to apply progressive loads makes it possible to determine the level at which the surface begins to show the defect considered in the assessment. This information allows different coatings to be compared and helps verify which finish offers greater resistance to marring under the specified test conditions.

Mar resistance is an important parameter for coatings used in applications where contact with other elements, handling operations or end use may generate visible marks on the surface. The test can therefore be used in finish development, qualification of coating cycles and routine verification of coating surface performance.

SAMAR536 is designed for testing in accordance with ISO 12137 and ASTM D5178, technical references for determining the Mar resistance of paints and coatings using a curved stylus on surfaces suitable for the method. The appropriate procedure should be selected based on the coating type, substrate and inspection criterion required.

The Mar resistance tester SAMAR536 provides a dedicated solution for evaluating surface damage on paints and coatings, identifying finish behaviour as the load applied during the Mar test progressively increases.

Applications

• Mar resistance testing on dried paints and coatings
• Assessment of Mar resistance of enamels and protective coatings
• Inspection of visible surface damage on finishes
• Comparison between different formulations or application cycles
• Verification of coated surfaces subject to contact and handling
• Quality-control checks on painted panels and samples
• Assessment of the load at which coating marring appears
• Mar testing with a curved loop-shaped stylus
• Testing in accordance with ISO 12137
• Testing in accordance with ASTM D5178

FAQ – Mar resistance tester

What is a Mar resistance tester used for?
It is used to assess the ability of a paint or coating to resist visible marks and surface damage caused by controlled mechanical actions.

What is a Mar resistance test?
It is a test used to determine the resistance of a coated surface to visible marring. The sample is moved beneath a loop-shaped stylus set at 45°, applying the load specified by the method until damage to the finish becomes visible.

How does SAMAR536 work?
The coated sample is moved beneath the loop-shaped stylus and subjected to the load specified for the test. The load is progressively increased until the coating reaches the point at which the surface damage defined by the inspection procedure first appears.

What does the Mar test result indicate?
The result makes it possible to assess the load level at which the finish shows the marring or visible damage specified by the method, allowing different coatings to be compared.

Why check the Mar resistance of a coating?
The inspection is useful where surface appearance must be maintained during handling, assembly or use.  A finish with limited resistance may show visible marks even without entire coating detachment.

Which coatings can SAMAR536 be used on?
It can be used on paints, enamels, protective finishes and coatings that are applied to samples compatible with the instrument configuration and selected test method.

Does the Mar test measure coating thickness?
No. This test does not measure film thickness; it assesses resistance to surface damage caused by marring.

Does the Mar test measure coating adhesion?
No. The test is intended to assess resistance to surface marring. Specific methods must be used to verify coating adhesion to the substrate.

In which activities can SAMAR536 be useful?
It is useful in finish and coating development, comparison of different application cycles and quality-control checks on painted surfaces where surface appearance is an important requirement.

Which standards does SAMAR536 refer to?
The instrument is used for testing in accordance with ISO 12137 and ASTM D5178, reference standards for determining the Mar resistance of paints and coatings.