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Definition: The standard tests according to Streicher and Strauss are standardised corrosion testing methods for assessing the resistance of stainless steels to intergranular corrosion. They serve to verify whether sensitisation due to chromium carbide precipitation is present. The methods are governed by DIN EN ISO 3651.

Practical relevance: The Strauss test (copper sulphate-sulphuric acid test) and the Streicher test (ferric sulphate-sulphuric acid test) examine the susceptibility to corrosion along grain boundaries. Mass loss, crack formation or microstructural attack are assessed after a defined exposure time. The tests are relevant after welding or heat treatment processes of austenitic steels.

Decision-making perspectives:

• Technical decision-makers: Ensuring the intergranular corrosion resistance of welded components.
• Purchasing/project management: Requiring standard-compliant test certificates for corrosion-critical applications.
• Science: Analysis of sensitisation mechanisms and carbide precipitation.
• Insurance/law: Verification of specification-compliant corrosion resistance in cases of damage.

Typical testing or verification methods: Strauss test, Streicher test, metallographic microstructure examination after exposure.

FAQ:

• When are Streicher or Strauss tests carried out?
• After welding or heat treatment processes to test for susceptibility to intergranular corrosion.

Definition: The stylus profilometry method is a tactile measurement technique for determining surface roughness, in which a diamond stylus tip traces the surface along a defined measurement length. The height profile is recorded and evaluated mathematically. The normative bases are DIN EN ISO 4287 and ISO 16610.

Practical relevance: Parameters such as Ra, Rz or Rt are calculated from the profile. The choice of cut-off wavelength (λc), filter type and measurement length significantly influences the result. The method is well established for the quality control of sealing faces, bearing locations and tribologically loaded components. The stylus tip radius and force must be matched to the surface.

Decision-making perspectives:

• Technical decision-makers: Ensuring function-appropriate roughness parameters for friction and sealing systems.
• Purchasing/project management: Clear specification of roughness parameters and measurement conditions in drawings.
• Science: Analysis of filtering methods and comparison with optical 3D topography.
• Insurance/law: Traceable verification of surface requirements in the event of functional deviations.

Typical testing or verification methods: Profile acquisition with a stylus instrument, filtering in accordance with ISO 16610, parameter evaluation (Ra, Rz).

FAQ:

• Why is the choice of filter important in the stylus profilometry method?
• It separates roughness from waviness and significantly influences the calculated parameters.