ISO 18089:2015 PDF

Corrosion of metals and alloys — Determination of the critical crevice temperature (CCT) for stainless steels under potentiostatic control

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Title (English):

ISO 18089:2015

Corrosion of metals and alloys — Determination of the critical crevice temperature (CCT) for stainless steels under potentiostatic control

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 13
Publication date:: November 5, 2015
Edition:: ISO IS 18089 edition 1 version 1
ICS:: 77.060

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Description (English):

ISO 18089:2015 describes the procedure for determining the critical crevice temperature (CCT) for stainless steels under potentiostatic control. The principal advantage of the test is the rapidity with which the CCT can be measured in a single test procedure. The CCT, as determined in this International Standard, can be used as a relative index of performance, for example, to compare the relative performance of different grades of stainless steel. The test described in this International Standard is not intended to determine the temperature at which crevice corrosion will occur in service. This method is not intended for materials with critical pitting temperature (CPT) values below 20 °C measured in accordance with ISO 17864, when measured in the same test solution and at the same potential

Technical details

Technical committee: ISO/TC 156 - Corrosion of metals and alloys
SKU: ISO 18089:2015

Abstract

Overview

ISO 18089:2015 specifies a laboratory procedure for determining the critical crevice temperature (CCT) of stainless steels under potentiostatic control. The method rapidly measures the lowest specimen surface temperature at which stable, propagating crevice corrosion occurs under defined electrochemical and environmental conditions. The CCT obtained is intended as a relative performance index (e.g., to compare stainless-steel grades), not as a prediction of in-service failure temperatures.

Key technical topics and requirements

Test principle: Heat the test solution to raise the specimen surface temperature at a controlled ramp rate while maintaining a set anodic potential with a potentiostat. Monitor current response to detect onset of crevice corrosion.
CCT definition: Temperature at which current density exceeds a specified value (recommended 10 μA·cm⁻²) for a sustained period (recommended 60 s) to indicate stable crevice propagation.
Equipment:
- Potentiostat capable of controlling potential to within ±1 mV.
- High‑input-impedance electrode potential measurement (sensitivity ≈1.0 mV).
- Auxiliary electrode (high‑purity platinum) and a reference electrode (Ag/AgCl preferred) connected via a Luggin capillary.
- Temperature controller/heating bath, stirring mechanism, and temperature probe (solution temperature accuracy ±1 °C).
- Crevice formers or specimen holders as described in Annex B.
Specimen and solution:
- Minimum specimen area guidance and reproducible surface finish (abrasion, cleaning, 24 h air ageing to form stable oxide).
- Test solutions commonly chloride‑containing; reagent‑grade chemicals and high‑purity water (see ISO 3696).
- Volume-to-area ratio and stir‑rate requirements to ensure repeatability (solution volume ≥100 ml per cm² specimen area).
Procedure controls:
- Start temperature depends on expected CCT (e.g., ~2 ± 1 °C for CCT

Related standards

Mentioned in the description and other ISO standards

Overview

Key technical topics and requirements

Test principle: Heat the test solution to raise the specimen surface temperature at a controlled ramp rate while maintaining a set anodic potential with a potentiostat. Monitor current response to detect onset of crevice corrosion.
CCT definition: Temperature at which current density exceeds a specified value (recommended 10 μA·cm⁻²) for a sustained period (recommended 60 s) to indicate stable crevice propagation.
Equipment:
- Potentiostat capable of controlling potential to within ±1 mV.
- High‑input-impedance electrode potential measurement (sensitivity ≈1.0 mV).
- Auxiliary electrode (high‑purity platinum) and a reference electrode (Ag/AgCl preferred) connected via a Luggin capillary.
- Temperature controller/heating bath, stirring mechanism, and temperature probe (solution temperature accuracy ±1 °C).
- Crevice formers or specimen holders as described in Annex B.
Specimen and solution:
- Minimum specimen area guidance and reproducible surface finish (abrasion, cleaning, 24 h air ageing to form stable oxide).
- Test solutions commonly chloride‑containing; reagent‑grade chemicals and high‑purity water (see ISO 3696).
- Volume-to-area ratio and stir‑rate requirements to ensure repeatability (solution volume ≥100 ml per cm² specimen area).
Procedure controls:
- Start temperature depends on expected CCT (e.g., ~2 ± 1 °C for CCT

ISO 18089:2015 PDF

Technical details

Abstract

Overview

Key technical topics and requirements

Related standards

Abstract

Overview

Key technical topics and requirements

Related standards

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