Overview
EN ISO 3651-2:1998 specifies standard methods for determining the resistance of stainless steels to intergranular corrosion in media containing sulfuric acid. This European standard applies to ferritic, austenitic, and ferritic-austenitic (duplex) stainless steels supplied as cast, rolled, or forged products, as well as tubes. The corrosion tests described are particularly relevant for materials intended to be used in mildly oxidizing acid environments, such as those containing sulfuric or phosphoric acid. These methods are commonly referred to as the Monypenny Strauss tests and serve as crucial quality control tools in manufacturing and fabrication settings.
Key Topics
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Material Scope:
- Applies to a wide range of stainless steels, including ferritic, austenitic, and duplex grades.
- Relevant for products in cast, rolled, forged, or tubular forms.
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Test Methods:
- Method A: 16% sulfuric acid/copper sulfate test (Monypenny Strauss test).
- Method B: 35% sulfuric acid/copper sulfate test.
- Method C: 40% sulfuric acid/ferric sulfate test.
- Selection of the appropriate method depends on steel composition and intended application.
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Test Purpose:
- Verification of the intrinsic resistance of the steel to intergranular corrosion, especially for low-carbon or stabilized grades.
- Inspection of solution treatment effectiveness, mainly for thin products.
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Testing Procedure:
- Involves exposing prepared test pieces to specified corrosive solutions under controlled conditions (boiling, specific durations).
- Assessment includes bend or flattening tests followed by visual examination for cracks indicating intergranular corrosion.
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Evaluation:
- Focuses on the presence of cracks post-corrosion testing as an indicator of susceptibility.
- Test results support quality assurance but are specific to resistance against intergranular corrosion in the tested medium.
Applications
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Quality Control: Used by manufacturers of stainless steel products to ensure compliance with corrosion resistance specifications, particularly before deployment in chemical processing, petrochemical, food processing, and other industries where exposure to acidic environments is expected.
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Material Selection: Assists engineers and material specifiers in choosing suitable stainless steel grades for use in environments with mildly oxidizing acids, thus helping to avoid premature material failure.
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Weld Assessment: Provides a protocol for evaluating the effect of welding on corrosion resistance, which is essential in the fabrication of tubes, pressure vessels, and process equipment.
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Product Certification: Supports third-party inspection, certification, and validation of critical components in industries requiring high safety and reliability standards.
Related Standards
- EN ISO 3651-1: Deals with intergranular corrosion testing of austenitic and duplex stainless steels in nitric acid (Huey test).
- ASTM A262: Practice for detecting susceptibility to intergranular attack in austenitic stainless steels.
- BS 5903: Methods for detecting susceptibility to intergranular corrosion in stainless steels.
- DIN 50914: Germany's national standard for intergranular corrosion testing.
- JIS G0575: Japanese standard for testing intergranular corrosion resistance.
- NF A 05-159: French standard for intergranular corrosion testing.
By referencing and aligning with EN ISO 3651-2:1998, organizations can ensure standardized evaluation of stainless steel corrosion resistance, contributing to product reliability and lifecycle extension in corrosive environments. Ensuring compliance with these corrosion tests enhances material durability, supports regulatory adherence, and reduces maintenance costs over the product life cycle.