Overview
ISO 21610:2009 defines accelerated corrosion tests to determine the intergranular corrosion susceptibility of austenitic stainless steels. The standard specifies two accelerated procedures that produce results equivalent to ISO 3651‑1 and ISO 3651‑2 but with a shorter test period. ISO 21610 is applicable to a wide range of product forms including two‑layer rolled metal, welded joints, deposited metal and weld seam metal.
Key topics and requirements
- Two test methods
- Method A: corrosion in a solution of copper sulfate (CuSO4·5H2O) and concentrated sulfuric acid (H2SO4) in the presence of metallic copper (copper filings or suspended copper plates).
- Method B: corrosion in a solution containing copper sulfate, sulfuric acid and copper fluoride with metallic copper present (accelerated variant described in the standard).
- Equivalence to ISO 3651: Provides identical pass/fail outcomes to ISO 3651‑1/‑2 but with reduced exposure time.
- Specimen types and preparation
- Flat, ring, segment, tubular and cylindrical specimens may be used depending on product form (plates, tubes, forgings, welds).
- Specimen finish: controlled surface roughness not to exceed 0.8 µm before testing.
- Mechanical requirements for bending/flattening to reveal intergranular cracks (e.g., bend to 90° for small specimens).
- Marking, degreasing and specific etching or electrochemical cleaning procedures for scale removal.
- Sensitization treatment
- Non‑stabilized steels: often tested as‑delivered unless carbon content or use conditions indicate otherwise.
- Stabilized steels (containing Ti or Nb) with low carbon may require a sensitization heat treatment (example: up to 700 ±10 °C for 30 min followed by water cooling) unless documented otherwise.
- Test vessel and copper contact: specimens are tested in a glass or corrosion‑resistant vessel with a copper layer or filings beneath specimens to promote accelerated attack.
- Test reporting: requirements for documenting specimen type, heat treatment, test method (A or B), and results.
Applications
- Material qualification and quality control of austenitic stainless steels for chemical, petrochemical, power generation and marine industries.
- Assessment of welded joints, clad/bimetallic products, deposited metal and weld seam metal for susceptibility to intergranular corrosion.
- Use by metallurgists, corrosion engineers, weld inspectors, QA/QC laboratories and standards compliance teams performing accelerated intergranular corrosion testing.
Related standards
- ISO 3651 (all parts) - Determination of resistance to intergranular corrosion of stainless steels (reference methods ISO 21610 accelerates).
- ISO 8044 - Corrosion of metals and alloys - Basic terms and definitions.
Keywords: ISO 21610:2009, intergranular corrosion, austenitic stainless steels, accelerated corrosion test, copper sulfate, sulfuric acid, copper fluoride, weld testing, sensitization heat treatment, ISO 3651.