ASTM G44: Standard Practice for Exposure of Metals and Alloys by Alternate Immersion in 3.5% NaCl
ASTM G44 is a standard practice for evaluating the stress corrosion cracking (SCC) susceptibility of metals and alloys through alternate immersion testing in a 3.5% sodium chloride solution. This cyclic wet-dry exposure creates a highly corrosive environment that accelerates SCC and exfoliation corrosion mechanisms, providing critical data for alloy selection and heat treatment qualification in the aerospace, marine, oil and gas, and structural engineering industries. For companies seeking ASTM G44 testing at a US-based testing lab, Infinita Lab provides comprehensive corrosion evaluation through its accredited laboratory network.
How ASTM G44 Testing Works
Stressed test specimens (C-ring, U-bend, or tension-loaded) are alternately immersed in 3.5% NaCl solution and exposed to air on a timed cycle—typically 10 minutes immersed followed by 50 minutes in air, repeated continuously. The wet-dry cycling creates an aggressive environment where the oxygen-rich drying phase accelerates electrochemical corrosion at the waterline and in crevices, more closely simulating marine and industrial atmospheric exposure than continuous immersion.
Specimen Types and Loading Methods
C-Ring Specimens (ASTM G38)
C-rings machined from rings or tubes are deflected with a bolt to apply sustained tensile stress. Different orientations evaluate SCC susceptibility in the short transverse, long transverse, and longitudinal grain directions of wrought aluminium and steel alloys.
U-Bend Specimens (ASTM G30)
Flat strips bent into U-shapes and held with a bolt create sustained tensile stress on the outer surface. U-bends are widely used to screen for SCC susceptibility in stainless steels and nickel alloys.
Industry Applications
ASTM G44 testing supports high-strength aluminium alloy temper qualification for the aerospace sector, stainless steel and nickel alloy SCC evaluation for petrochemical service, marine hardware and fastener material selection, and structural steel heat treatment validation for the construction industry.
Why Choose Infinita Lab for Corrosion Testing?
At the core of this breadth is our network of 2,000+ accredited labs in the USA, offering access to over 10,000 test types. From advanced metrology (SEM, TEM, RBS, XPS) to mechanical, dielectric, environmental, and standardised ASTM/ISO testing, we give clients unmatched flexibility, specialisation, and scale. You are not limited by geography, facility, or methodology—Infinita connects you to the right testing, every time.
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Frequently Asked Questions (FAQs)
What does the ASTM G44 test? ASTM G44 evaluates the stress-corrosion cracking susceptibility of metals and alloys by alternate immersion in a 3.5% NaCl solution, simulating aggressive marine and industrial atmospheric environments.
Why is alternate immersion more aggressive than continuous immersion? The wet-dry cycling concentrates salt at the surface during drying, creates differential aeration cells, and allows oxygen-rich air access during the dry phase—all of which accelerate electrochemical corrosion and SCC.
What specimen types are used with ASTM G44? C-rings (ASTM G38), U-bends (ASTM G30), and direct tension specimens under constant load are the primary specimen types for sustained-load SCC evaluation during alternate immersion exposure.
How long does ASTM G44 testing take? Typical exposure durations range from 20 to 90 days, depending on the alloy system and specification requirements. Aluminium SCC testing typically requires 20–30 days; stainless steel testing may take 90+ days.
What metals are most commonly tested per ASTM G44? High-strength aluminum alloys (2xxx, 7xxx series), austenitic and duplex stainless steels, nickel alloys, carbon steels, and copper alloys are the most commonly evaluated materials for SCC susceptibility.
