Overview
ISO 7539-8:2000, "Corrosion of metals and alloys - Stress corrosion testing - Part 8: Preparation and use of specimens to evaluate weldments," specifies guidance for stress corrosion testing of welded specimens. It outlines how welding affects corrosion and mechanical behaviour, and gives recommendations for selecting and preparing test specimens and procedures to assess the resistance of weldments to stress corrosion and stress corrosion cracking (SCC).
Key topics and requirements
- Scope and intent: Procedures for stress corrosion testing of welded specimens and additional factors unique to weldments that influence corrosion and SCC.
- Weldment considerations:
- Residual welding stresses and stress concentration effects from shrinkage and weld geometry.
- Microstructural changes in the heat affected zone (HAZ) and cast-like structure of weld metal.
- Non‑metallic inclusions and defect risks (microcracking, lack of fusion, porosity) - weld examination is recommended to assess whether failures arise from pre-existing defects or from SCC.
- Recommendation to characterize weldments for residual stress, surface condition and defects prior to testing.
- Specimen types: Descriptions and uses of common specimen geometries for weldment testing, including:
- Flat weldments, circular bead, bead-on-bar
- Direct tension specimens, U-bend, bent-beam
- Pre-cracked specimens, C-ring and slit-tube specimens
- Preparation and welding records: Test reproducibility requires consistent welding conditions and following a Welding Procedure Specification (WPS). Clause 6.1 lists WPS elements such as type of weld, parent metal and thickness, weld preparation, consumable type, shielding gas, welding process, arc voltage/current, travel speed, number of passes, heat input, preheat/interpass temperatures, sequence of passes, and post-weld treatment.
- Testing, assessment and reporting: The standard references test procedures, assessment of results and required test-report content (clauses on procedures, assessment and test report are provided).
Practical applications and users
ISO 7539-8 is used by:
- Corrosion and materials engineers assessing welded components for SCC risk.
- Welding engineers and quality control laboratories validating welding procedures and post‑weld treatments.
- R&D groups developing weld metallurgy, and asset owners in industries with welded structures (pipelines, pressure equipment, power generation, petrochemical and fabrication) that need validated stress corrosion testing of weldments.
Keywords: ISO 7539-8, stress corrosion testing, weldments, weld specimen preparation, stress corrosion cracking, welding procedure specification, heat affected zone, residual stresses.
Related standards
- ISO 7539 (Parts 1–7, 9) - general guidance and specimen preparation methods (bent-beam, U-bend, tension, C‑ring, pre-cracked, slow strain rate, etc.)
- ISO 857-1:1998 (welding vocabulary)
- IEC 60050-851 (electric welding vocabulary)
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