Corrosion Problems in Forged Components
Corrosion failures are almost always specification failures. The environment was described loosely, a grade was chosen on price, and the part met a condition nobody wrote down.
Corrosion in forged parts usually traces to grade selection against a loosely described environment. SS 304 pits in chlorides where SS 316 survives; duplex is needed where chloride stress corrosion cracking threatens. Carbon contamination during handling and inadequate transit protection are the other common causes.
- Chlorides present
- SS 316 minimum, duplex if SCC risk
- No chlorides
- SS 304 usually sufficient
- Hardness needed too
- SS 410 martensitic
- Stainless handling
- Fully segregated from carbon steel
- Sea transit
- VCI film plus desiccant
Corrosion Problems in Forged Components at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- SS 316's molybdenum resists chloride pitting
- Duplex resists chloride stress corrosion cracking
- Stainless is processed on segregated tooling here
- VCI plus desiccant protects sea freight consignments
Grade Chosen for the Wrong Environment
SS 304 in a chloride environment pits within months. Carbon steel with a coating in continuous immersion fails where the coating is damaged. Duplex is needed where chloride stress corrosion cracking threatens. The environment must be described specifically — medium, temperature, concentration — not just as 'corrosive'.
- 304 pits in chlorides; use 316
- Coatings fail at damage points
- Duplex resists chloride SCC
- Describe medium, temperature, concentration
Carbon Contamination and Transit Rust
Stainless handled on tooling shared with carbon steel picks up embedded iron that rusts weeks later, looking exactly like a grade failure. Segregated handling prevents it. Separately, sea transit without VCI and desiccant protection produces surface rust that arrives looking like a quality failure.
People also ask
Why does stainless steel rust after machining?
Usually from embedded iron picked up from tooling or handling shared with carbon steel. Segregated handling and passivation prevent it.
What information does a supplier need to recommend a grade?
The medium, its concentration, operating temperature, whether chlorides are present, and whether the part is under tensile stress in service.
Is passivation necessary on stainless forgings?
It is recommended after machining, since it restores the chromium oxide layer and removes free iron from the surface.
Topics covered on this page
- corrosion
- chloride pitting
- stress corrosion cracking
- SS 316
- duplex stainless
- passivation
- carbon contamination
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
Why did my stainless steel part rust?
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Either the grade was wrong for the chloride exposure, or carbon steel contamination was embedded during handling and is rusting on the surface.
Which stainless resists chlorides?
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SS 316 as a minimum, thanks to its molybdenum content. Duplex where chloride stress corrosion cracking is a realistic risk.
How do you prevent rust during shipping?
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VCI film, desiccant and rust-preventive oil, with the protection level chosen for the specific route and transit duration.