Does SS 316 Stainless Steel Suffer From Intergranular Corrosion?

Stainless steel 316 (EN 1.4401 / UNS S31600) is widely used in chemical, marine, and food processing industries due to its superior corrosion resistance. However, like other austenitic stainless steels, SS 316 can suffer from intergranular corrosion under certain conditions.

This article explains why intergranular corrosion occurs, how to detect it, and how 316 PMI testing can prevent material mix-ups. It also compares 316 vs 316L corrosion resistance, highlights welding corrosion risks, and provides guidance for procurement and quality assurance.

 

 

What Is Intergranular Corrosion in SS 316?

Intergranular corrosion (IGC) is a localized attack along grain boundaries of stainless steel. It typically occurs after high-temperature exposure, such as welding or heat treatment between 450–850°C, leading to chromium carbide precipitation.This phenomenon compromises the 316 stainless steel grain boundary corrosion resistance, even though the bulk material remains largely unaffected.

Why SS 316 May Be Susceptible

Factor	Effect on 316 Stainless Steel
Welding	Heat-affected zones may precipitate chromium carbides
Carbon content	High carbon increases sensitization risk
Temperature	450–850°C exposure can trigger intergranular corrosion
Environment	Chloride-rich environments exacerbate corrosion

Key insight for buyers: Even high-quality SS 316 can suffer from intergranular corrosion if heat treatment and welding practices are improper.

 

316 vs 316L Corrosion Resistance

Property	SS 316	SS 316L
Carbon Content	≤0.08%	≤0.03%
Susceptibility to IGC	Moderate	Low
Weldability	Good, may require post-weld annealing	Excellent, no post-weld annealing needed
Typical Applications	Chemical & marine components	Pressure vessels, welding-critical projects

316L is often recommended for welded components because it minimizes welding corrosion of 316 stainless steel and intergranular attack.

 

Preventing Intergranular Corrosion in SS 316

Solution	Explanation
Use Low-Carbon 316L	Reduces chromium carbide precipitation
Proper Welding Practices	Control heat input and minimize dwell time
Solution Annealing	Heat treatment to dissolve carbides
Specify ASTM A262 Testing	Ensures material meets corrosion resistance requirements
PMI Testing	Confirms chemical composition before installation

 

FAQ

Q1: Does SS 316 stainless steel corrode easily at grain boundaries?
Yes, if it is sensitized by welding or high-temperature exposure.

Q2: How is intergranular corrosion detected in 316 stainless steel?
Through ASTM A262 testing, metallography, and chemical analysis including 316 PMI testing.

Q3: Should I choose 316 or 316L for welding applications?
For welded components, 316L is preferred due to lower carbon content and reduced intergranular corrosion risk.

Q4: Can PMI testing distinguish 316 from 316L or 304?
Yes. 316 PMI testing can confirm molybdenum content and verify the correct stainless steel grade.