A4 Stainless Steel Foundation Bolts, L and J Form combine the dimensional form of Trade series (cast-in holding-down bolt) with the material properties of grade ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80: superior, including marine and chloride environments, largely non-magnetic, service range approx. -200 °C to +400 °C, subject to the property class and the joint. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose A4 Stainless Steel for Foundation Bolts, L and J Form
Specified for marine, coastal and chemical applications. For foundation bolts, l and j form, 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 |
Galvanic & Galling Considerations
Two important notes for stainless foundation bolts, l and j form: (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.
Comparable Grades
For Foundation Bolts, L and J Form, 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
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Foundation Bolts, L and J Form Available in A4 Stainless Steel
| Thread size | Form | Overall length L (mm) | Hook length (mm) | Thread length (mm) | Projection above concrete (mm) | Material | Finish |
|---|---|---|---|---|---|---|---|
| M12 | L | 300 | 50 | 60 | 60 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M16 | L | 400 | 65 | 80 | 80 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M16 | J | 400 | 80 | 80 | 80 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M20 | L | 500 | 80 | 100 | 100 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M20 | J | 500 | 100 | 100 | 100 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M24 | L | 600 | 100 | 120 | 120 | Class 4.6 / 8.8 steel | Hot-dip galvanised |
| M30 | L | 750 | 120 | 150 | 150 | Class 4.6 steel | Hot-dip galvanised |
