Stainless Steel Fittings: 304 vs 316 and How to Choose
Stainless fittings carry the corrosive, sanitary, and high-purity services that carbon steel and brass can't. The two decisions that matter most: which alloy, and which connection style. Get those right and the fitting outlasts the pipe around it.
304 vs 316: The Molybdenum Difference
Both are 18-8 austenitic stainless; 316 adds 2–3% molybdenum, which buys dramatically better resistance to chlorides and acids. Practical rule: 304 for fresh water, food service, general atmosphere, and mild chemicals; 316/316L for anything with chlorides — coastal Gulf Coast plants, brine, seawater, bleach — plus sulfuric and most process acids. The "L" grades (low carbon) resist sensitization at weld zones and are the default for welded systems. If you're within a few miles of salt water, 316 pays for itself in avoided tea-staining and pitting.
Connection Styles
| Type | Best for |
|---|---|
| Threaded (NPT), Class 150 & 3000 | Instrument lines, utility piping, easy service |
| Socket weld, Class 3000/6000 | Small-bore high-pressure process lines |
| Butt weld (B16.9) | Full-flow process piping, radiographed systems |
| Compression / instrumentation | Tubing systems, gauges, analyzers |
| Tri-clamp sanitary | Pharma, food, clean-in-place systems |
Pressure Classes, Briefly
Cast Class 150 threaded fittings cover utility duties; forged Class 3000 (A182 F304/F316) is the standard for process plants and matches Schedule 80 pipe strength. Ratings de-rate with temperature — check B16.11 tables above ambient. For hydraulic and instrument tubing, use properly gapped compression fittings rather than adapting pipe fittings.
Thread Sealing on Stainless
Stainless-to-stainless threads gall. Always use PTFE tape plus an anti-seize-bearing paste sealant, assemble slowly, and avoid impact guns. Galled threads can't be repaired — only cut out.
Stainless From the Shelf
We stock 304 and 316 threaded, socket weld, and sanitary fittings alongside the hose, gaskets, and bolting that complete the system. Send sizes, class, and quantities through the quote form at the top of this page — pricing and lead time back in 1–2 business hours.