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). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
Using Stainless Fasteners in Aluminum
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
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) | Common length range (mm) | Reference standard |
|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 8 | 3.5 | 10 | 1.0 | 8~40 | DIN 933 + BS 4518 |
| M6 | 1.0 | 10 | 4.0 | 12 | 1.5 | 10~50 | DIN 933 + BS 4518 |
| M8 | 1.25 | 13 | 5.3 | 14 | 1.5 | 12~60 | DIN 933 + BS 4518 |
| M10 | 1.5 | 17 | 6.4 | 16 | 1.5 | 16~60 | DIN 933 + BS 4518 |
| M12 | 1.75 | 19 | 7.5 | 19 | 2.0 | 20~80 | DIN 933 + BS 4518 |
| M16 | 2.0 | 24 | 10.0 | 24 | 2.0 | 25~80 | DIN 933 + BS 4518 |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A4 Stainless Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
