For hex bolts, grade c in A4 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is summarized below together with every size supplied.
Why Choose A4 Stainless Steel for Hex Bolts, Grade C
Specified for marine, coastal and chemical applications. For hex bolts, grade c, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Hex Bolts, Grade C in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless hex bolts, grade c: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Hex Bolts, Grade C Available in A4 Stainless Steel
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M5 | 0.8 | 8.0 | 8.63 | 3.35 | Grade C | ISO 4016 / DIN 601 |
| M6 | 1.0 | 10.0 | 10.89 | 4.15 | Grade C | ISO 4016 / DIN 601 |
| M8 | 1.25 | 13.0 | 14.2 | 5.45 | Grade C | ISO 4016 / DIN 601 |
| M10 | 1.5 | 17.0 | 18.72 | 6.58 | Grade C | ISO 4016 / DIN 601 |
| M12 | 1.75 | 19.0 | 20.88 | 7.68 | Grade C | ISO 4016 / DIN 601 |
| M14 | 2.0 | 22.0 | 24.49 | 9.25 | Grade C | ISO 4016 / DIN 601 |
| M16 | 2.0 | 24.0 | 26.75 | 10.18 | Grade C | ISO 4016 / DIN 601 |
| M18 | 2.5 | 27.0 | 29.56 | 11.72 | Grade C | ISO 4016 / DIN 601 |
| M20 | 2.5 | 30.0 | 33.53 | 12.72 | Grade C | ISO 4016 / DIN 601 |
| M22 | 2.5 | 32.0 | 35.72 | 14.5 | Grade C | ISO 4016 / DIN 601 |
| M24 | 3.0 | 36.0 | 39.55 | 15.35 | Grade C | ISO 4016 / DIN 601 |
| M27 | 3.0 | 41.0 | 45.2 | 17.92 | Grade C | ISO 4016 / DIN 601 |
| M30 | 3.5 | 46.0 | 50.85 | 19.75 | Grade C | ISO 4016 / DIN 601 |
| M36 | 4.0 | 55.0 | 60.79 | 23.35 | Grade C | ISO 4016 / DIN 601 |
| M42 | 4.5 | 65.0 | 71.3 | 27.05 | Grade C | ISO 4016 / DIN 601 |
| M48 | 5.0 | 75.0 | 82.6 | 31.07 | Grade C | ISO 4016 / DIN 601 |
