ASTM G47-22 PDF

Overview

ASTM G47-22: Standard Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX Aluminum Alloy Products provides a uniform procedure for evaluating the resistance of high-strength aluminum alloy wrought products to stress-corrosion cracking (SCC). This method is especially relevant for 2XXX (copper content 1.8% to 7.0%) and 7XXX (copper content 0.4% to 2.8%) aluminum alloys, focusing primarily on products stressed in the short-transverse direction relative to the grain structure. The standard guides material engineers, test laboratories, and those preparing stress-corrosion specifications in assessing SCC susceptibility for quality assurance and material selection.

Key Topics

• Test Method Scope Covers sampling, specimen preparation, test environments, and exposure procedures tailored for 2XXX and 7XXX aluminum alloys.
• SCC Detection Utilizes alternate immersion in 3.5% sodium chloride (NaCl) solution, simulating aggressive, marine-influenced service environments.
• Test Specimens Details types (e.g., tension, C-ring), sizes, and orientations-especially stressing short-transverse to the grain structure for optimal SCC sensitivity.
• Interpretation of Results Specifies criteria for SCC failure, including metallographic examination and differentiation from other forms of corrosion such as pitting.
• Precision and Bias Supported by interlaboratory test programs to verify reproducibility and consistency among different laboratories for common alloy tempers.

Applications

ASTM G47-22 is widely adopted across industries that utilize high-strength aluminum alloys, including:

• Aerospace Used in qualifying aluminum materials intended for aircraft components exposed to marine or corrosive atmospheres, ensuring mechanical integrity and reliability.
• Marine Engineering Assesses alloys for shipbuilding and offshore structures where saltwater-induced SCC is a concern.
• Automotive and Transportation Ensures the selection of SCC-resistant aluminum alloys for performance-critical vehicle parts.
• Manufacturing and Fabrication Assists suppliers and manufacturers in verifying material certification and fitness for environments prone to chloride exposure and mechanical stress.

This test method is particularly valuable for materials selection, quality control, and as a reference in supply chain contracts involving 2XXX and 7XXX series alloys. While it simulates marine environments, actual service circumstances may warrant additional or alternative tests tailored to specific conditions and protective measures.

Related Standards

ASTM G47-22 references and complements several other ASTM standards, supporting a comprehensive approach to stress-corrosion testing:

• ASTM G38 - Practice for Making and Using C-Ring Stress-Corrosion Test Specimens Details the preparation and use of C-ring specimens for SCC assessment.

• ASTM G44 - Practice for Exposure of Metals and Alloys by Alternate Immersion in NaCl Solution Specifies alternate immersion protocols, including the 3.5% NaCl solution used in G47.

• ASTM G49 - Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens Outlines the methods for preparing and loading tension specimens for SCC testing.

• ASTM G139 - Test Method for Determining Stress-Corrosion Cracking Resistance by Breaking Load Method Offers an alternative approach for evaluating SCC resistance in heat-treatable aluminum alloys.

These related standards, alongside ASTM G47-22, form an essential toolkit for SCC evaluation, ensuring consistency and reliability in the testing and selection of corrosion-resistant aluminum alloys for demanding service environments.

Keywords: stress-corrosion cracking, SCC, aluminum alloys, 2XXX, 7XXX, ASTM G47, marine environments, alternate immersion, test method, material qualification, corrosion resistance, quality assurance, tension specimen, C-ring specimen.