ASTM A262 Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels

In ASTM A262, considering practice A, it is used for acceptance of wrought or cast austenitic steel material but not for rejection of materials. This method is intended to be used along with other evaluation tests like Practice B, C, D, E, and F to provide a rapid method to identify those specimens that are certain to be free from rapid intergranular attack.

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ASTM A262 Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM A262 provides a series of practices to evaluate the susceptibility of austenitic stainless steels to intergranular corrosion. This form of corrosion occurs along grain boundaries due to chromium depletion, often caused by improper heat treatment or welding.

The standard includes multiple test methods to detect sensitization and assess whether stainless steel materials are prone to intergranular attack. It is widely used in industries where corrosion resistance is critical, such as chemical processing, nuclear, and power generation.

Scope, Applications, and Benefits

Scope

ASTM A262 evaluates the resistance of austenitic stainless steels to intergranular attack using various practices, such as oxalic acid etching, nitric acid testing, and ferric sulfate-sulfuric acid exposure. The test identifies both sensitization and grain-boundary corrosion susceptibility.

The test evaluates:

Susceptibility to intergranular corrosion
Degree of sensitization in stainless steel
Grain boundary chromium depletion
Effect of heat treatment and welding
Corrosion resistance of austenitic stainless steels

Applications

Austenitic stainless steel components
Welded structures and heat-affected zones
Chemical and petrochemical equipment
Nuclear and power plant materials
Heat exchangers and piping systems
Corrosion resistance qualification testing

Benefits

Detects early signs of intergranular corrosion
Helps ensure proper heat treatment and processing
Supports material selection for corrosive environments
Assists in failure analysis and prevention
Enables comparison of corrosion resistance

Test Process

Sample Preparation

Specimens are cut, polished, and cleaned according to selected practice requirements.

Chemical Exposure

Samples are subjected to specific reagents such as oxalic acid or nitric acid depending on the method.

Corrosion Evaluation

Grain boundary attack or etching patterns are examined visually or microscopically.

Data Recording & Evaluation

Results are classified based on standard criteria to determine susceptibility.

Technical Specifications

Parameter	Details
Applicable Materials	Austenitic stainless steels (300 series)
Test Methods	Practices A, B, C, D, E, F
Oxalic Acid Test	10% solution, ~1 A/cm² for 90 sec
Nitric Acid Test	65% HNO₃, boiling (~120°C)
Exposure Duration	24 to 120 hours (method dependent)
Evaluation Criteria	Step, dual, or ditch structure classification

Instrumentation Used for Testing

Metallurgical microscope
Electrolytic etching setup
Boiling nitric acid test apparatus
Sample preparation and polishing equipment
Chemical handling systems
Data recording and analysis tools

Results and Deliverables

Intergranular corrosion susceptibility classification
Microstructural evaluation images
Sensitization assessment results
Comparative corrosion behavior analysis
Test condition summary
ASTM compliance report

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Frequently Asked Questions

ASTM A262 includes chemical composition, heat treatment condition, test solution type, exposure duration, and evaluation method, determining susceptibility of austenitic stainless steels to intergranular corrosion under controlled laboratory conditions.

ASTM A262 includes Practices A through F, such as oxalic acid etch, Strauss test, and Huey test, used to evaluate intergranular corrosion susceptibility.

ASTM A262 is commonly applied to austenitic stainless steels used in chemical processing, power generation, and structural applications where resistance to intergranular corrosion is critical.

ASTM A262 evaluates grain boundary attack, weight loss, and surface condition, indicating susceptibility to intergranular corrosion after exposure to specific test conditions.

ASTM A262 evaluates susceptibility under controlled laboratory conditions and may not fully represent service environments where temperature, stress, and chemical exposure influence corrosion behavior.