Intergranular Corrosion Of SS 316 Stainless Steel: Causes, Tests, And Prevention

Are you looking for information on the causes of intergranular corrosion in SS 316 stainless steel to ensure your materials meet corrosion resistance requirements in chemical, marine, or high-temperature applications? Many engineers and procurement specialists are seeking ways to prevent intergranular corrosion in 316 stainless steel, especially in welded components, heat exchangers, and piping systems. Understanding the causes of corrosion, testing methods, and preventative measures is crucial to avoiding material failure, production downtime, and costly replacements.

 

What Is Intergranular Corrosion in SS 316 Stainless Steel?

Intergranular corrosion (IGC) is a localized attack along the grain boundaries of austenitic stainless steels like SS 316. It often occurs when chromium carbides precipitate during high-temperature exposure (450–850°C). This can reduce corrosion resistance along grain boundaries, even if the bulk material appears unaffected.

 

 

Causes of SS316 Intergranular Corrosion

Factor	Mechanism	Effect on SS 316
Welding	Heat-affected zones cause chromium carbide precipitation	Weakens grain boundary corrosion resistance
High Carbon Content	C > 0.08% increases sensitization	Higher risk of intergranular corrosion
Thermal Exposure	450–850°C without solution annealing	Promotes carbide formation
Chloride Environment	Aggressive ions attack grain boundaries	Accelerates localized corrosion

Insight for buyers: Even standard SS 316 can suffer IGC if welding or heat treatment is not properly controlled.

 

316 vs 316L: Resistance to Intergranular Corrosion

Property	316 SS	316L SS
Carbon Content	≤ 0.08%	≤ 0.03%
IGC Susceptibility	Moderate	Low
Weldability	Good, may require post-weld heat treatment	Excellent, minimal sensitization
Applications	General chemical & marine use	Welded pressure vessels, heat exchangers

 

How to detect intergranular corrosion in SS316?

1. ASTM A262 Test for 316 Stainless Steel

Practice E (Strauss Test) detects sensitization

Measures susceptibility to grain boundary attack

Widely accepted by chemical, petrochemical, and food industries

2. Metallographic Examination

Microscope inspection of grain boundaries

Reveals chromium carbide precipitation

3. Chemical Analysis & PMI Testing

316 PMI testing (XRF / OES) confirms molybdenum content (2–3%)

Detects material mix-ups (316 vs 304 or 316L)

Ensures compliance with EN 1.4401 / ASTM A240 / UNS S31600

 

Click to download ASTM A262 intergranular corrosion tests

Preventive Measures for SS 316 Intergranular Corrosion

Prevention Method	Description
Use Low-Carbon 316L	Reduces carbide formation during welding or high-temperature exposure
Solution Annealing	Heat treatment (1040–1120°C) to dissolve carbides
Proper Welding	Control heat input, use correct filler metals, minimize dwell time
ASTM A262 Testing	Verify material is resistant to IGC
PMI Testing	Confirm chemical composition before installation

 

Key Takeaways for Procurement

SS 316 is generally corrosion-resistant, but grain boundary attack can occur in welded or high-temperature applications.

316L stainless steel is recommended when IGC risk must be minimized.

PMI testing and ASTM A262 are essential to verify grade authenticity and corrosion resistance.

Solution annealing, proper welding practices, and certified suppliers ensure reliable long-term performance.