For square plate washers (din 436) 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 Square Plate Washers (DIN 436)
Specified for marine, coastal and chemical applications. For square plate washers (din 436), 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 Square Plate Washers (DIN 436) in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
For stainless square plate washers (din 436) the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
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 Square Plate Washers (DIN 436) Available in A4 Stainless Steel
| For bolt size | Inner diameter d1 (mm) | Side length (mm) | Thickness t (mm) | Bearing area (mmu00b2) | Bearing vs DIN 125 washer | Material | Reference standard |
|---|---|---|---|---|---|---|---|
| M10 | 11 | 40 | 3 | 1505 | approx. 5.4x | Steel, hot-dip galvanised | DIN 436 |
| M12 | 14 | 50 | 4 | 2346 | approx. 5.8x | Steel, hot-dip galvanised | DIN 436 |
| M16 | 18 | 58 | 5 | 3110 | approx. 5.1x | Steel, hot-dip galvanised | DIN 436 |
| M20 | 22 | 68 | 6 | 4244 | approx. 5.2x | Steel, hot-dip galvanised | DIN 436 |
| M24 | 26 | 80 | 6 | 5869 | approx. 5.3x | Steel, hot-dip galvanised | DIN 436 |
