Material specification page for sealing screws with bonded washer in A4 Stainless Steel. Covers the grade designation (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to DIN 933.
Why Choose A4 Stainless Steel for Sealing Screws with Bonded Washer
Specified for marine, coastal and chemical applications. For sealing screws with bonded washer, 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 Sealing Screws with Bonded Washer in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Sealing Screws with Bonded Washer, the alternative stainless grade is A2 (304). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.
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 Sealing Screws with Bonded Washer Available in A4 Stainless Steel
| Thread size | Pitch (mm) | Across flats s (mm) | Head height k (mm) | Seal outer diameter (mm) | Seal thickness (mm) | Seal material | Common length range (mm) | Reference standard |
|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 8 | 3.5 | 10 | 1.0 | NBR | 8~40 | DIN 933 + BS 4518 |
| M6 | 1.0 | 10 | 4.0 | 12 | 1.5 | NBR | 10~50 | DIN 933 + BS 4518 |
| M8 | 1.25 | 13 | 5.3 | 14 | 1.5 | NBR | 12~60 | DIN 933 + BS 4518 |
| M10 | 1.5 | 17 | 6.4 | 16 | 1.5 | NBR | 16~60 | DIN 933 + BS 4518 |
| M12 | 1.75 | 19 | 7.5 | 19 | 2.0 | NBR | 20~80 | DIN 933 + BS 4518 |
| M16 | 2.0 | 24 | 10.0 | 24 | 2.0 | NBR | 25~80 | DIN 933 + BS 4518 |
