SS 316 / 316L / 316Ti Bolts Manufacturer & Exporter in India

All three grades share the same chromium-nickel-molybdenum base composition and offer equivalent corrosion resistance in most environments. The key differences are: SS 316 is the standard grade suitable for ambient and moderate-temperature service up to approximately 300°C. SS 316L limits carbon to 0.03% max, making it the correct choice for welded assemblies or heat-affected zone applications where intergranular corrosion (sensitisation) must be avoided – it is the most commonly specified grade for pharmaceutical, food, and chemical process flanges. SS 316Ti adds titanium stabilisation, making it the preferred grade for continuous service above 400°C up to 800°C where repeated thermal cycling would sensitise even 316L over time. For ambient and moderate-temperature service, 316L is the safest default. Specify 316Ti only when sustained elevated temperature is confirmed.

SS 316 bolts provide good resistance to seawater splash and atmospheric marine exposure, but are not recommended for continuous full seawater immersion, particularly in crevice-prone geometries such as under bolt heads and between mating flanges. In immersed seawater, the PREN of 24-26 is insufficient to prevent crevice corrosion at ambient temperature over extended service periods. For continuous seawater immersion, duplex SS 2205 (PREN 35+) or super duplex SS 2507 (PREN 42+) bolts are recommended. SS 316 bolts perform reliably in splash zones, tidal zones, and atmospheric marine environments with appropriate maintenance intervals.

Austenitic stainless steel fasteners are highly susceptible to galling (cold welding of threads) when torqued without lubrication, particularly in stainless-to-stainless assemblies. Always apply a PTFE-based or molybdenum disulphide anti-seize compound to bolt threads and nut bearing faces before assembly. Reduce target torque values by 15-20% compared to dry values. Tighten at a slow, steady rate – avoid impact wrenches on stainless threads. If a bolt begins to seize during tightening, back off immediately and re-lubricate. Using a stainless bolt with a slightly different alloy nut (e.g., 316 bolt with 304 nut) can also reduce galling risk in non-corrosive environments.

Yes – SS 316L is the standard fastener material for FDA-regulated pharmaceutical manufacturing equipment, food processing machinery, and beverage plant pipework. The low carbon content meets GMP requirements, and the molybdenum content provides resistance to cleaning chemicals including dilute nitric acid, citric acid, and sodium hypochlorite CIP solutions. Surface finish options include electropolished (Ra = 0.4 µm) and passivated per ASTM A967 for hygienic applications. 3-A Sanitary Standards and EHEDG guidelines both accept SS 316L as a compliant contact-surface material for food and pharmaceutical fasteners.