Physical test procedures

Hardness testing

A further property of materials and their coatings is their hardness. Hardness is determined as a Vickers reading in a range of test forces from 10 g to 1000 g to DIN EN ISO 6507 and DIN EN ISO 4516 for micro-indentation tests.

Layer hardness can be determined both on the cross-section edge and perpendicular to the surface. However, measurement on the cross-sectional edge is often unavoidable because surface roughness makes measurement of the indentations perpendicular to the surface impossible.

These hardness measurements are suitable for:

  • Coating hardness - Vickers micro-indentation tests HV0.01 to HV0.2 using test forces of 10 g to 200 g
  • Hardness profiles after boundary layer hardening, such as hardness penetration profiles in heat-treated parts to DIN EN 10328 and to determine case depths.

Equipment:

Tensile and compression tests

Tensile tests are used to determine the strength and deformation characteristics of materials using loads applied in a uniaxial direction, uniformly spread over the cross-section in accordance with DIN EN ISO 6892-1.

The specimen is uniformly and smoothly drawn until it ruptures.

Suitable for:

  • Testing of the adherence characteristics of various coatings
  • Tensile and compression tests from 0.1 to 50 kN
  • Tests for hydrogen embrittlement in static tensile loading

Equipment:

Roughness measurements (geometrical product specifications GPS)

Profile method for determining the surface finish and standard characteristics to DIN EN ISO 4287 and DIN EN ISO 4288.

Measuring principle:

The surface of the specimen being examined is traced with a diamond-tipped needle. The vertical displacement of the needle is recorded by a path measurement system and the computer produces a 2D profile.

The objective is to determine key roughness values such as arithmetic mean surface roughness Ra, or the surface roughness depth Rz, maximum surface roughness Rmax or other standardised characteristics, depending on the application.

Equipment:

Abrasion testing, abrasion wheel method

Determining the abrasion resistance of various materials using a TABER® Rotary Platform Abrasion Tester or Taber Abraser. Suitable for metals, paint finishes, lacquer and paint coatings and galvanic coatings.

Measuring principle:

The abrasive action is generated by a pair of discs that are pressed onto the revolving specimen with a defined force. The surface is processed isotropically. Evaluation is normally carried out on the basis of weight loss. However, it is also possible to evaluate the results based on the depth of the abraded track e.g. by measuring the profile by means of the profile method or evaluation of the resistance of the coating to through-abrasion.

Equipment:

Thermal bond test/ mandrel bending test

Evaluation of adhesive strength and extensibility of electrochemical coatings and dry paint finishes on thin test panels in accordance with DIN EN ISO 1519.

Measuring principle:

Method 1. As a "pass/fail" test, by bending the coated substrate several times around a single specified size of mandrel. After a predefined number of test bends, the extent to which the coating has separated from the substrate or flaked off is assessed and thus whether the requirements have been met.

Method 2. Repeated tests using successively smaller mandrels to determine the diameter of the first mandrel over which the coating cracks and/or becomes detached from the substrate.

Cross-cut adhesion test

This is a quick tests to assess the adhesive strength of single or multiple layer systems
in accordance with DIN EN ISO 2409.

Measuring principle:

A cutting tool is used to cut a grid shaped pattern through the coating down to the substrate. This is followed by a tape test. The number of detached segments provides a guide to the adhesive strength of the coating.