Masonry Screws, Countersunk Torx manufactured in A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) are dimensioned to Trade series (hardened high-low thread). The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose A4 Stainless Steel for Masonry Screws, Countersunk Torx
Specified for marine, coastal and chemical applications. For masonry screws, countersunk torx, 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 Masonry Screws, Countersunk Torx in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Masonry Screws, Countersunk Torx, the alternative stainless grade is A2 (304). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
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 Masonry Screws, Countersunk Torx Available in A4 Stainless Steel
| Nominal diameter d (mm) | Drill hole diameter (mm) | Head diameter dk (mm) | Head height k (mm) | Drive | Minimum embedment (mm) | Common length range (mm) | Substrate note |
|---|---|---|---|---|---|---|---|
| 6.3 | 5.0 | 13.0 | 3.5 | TX30 | 25 | 40~120 | Concrete, solid brick |
| 7.5 | 6.0 | 15.0 | 4.0 | TX30 | 30 | 50~160 | Concrete, solid brick |
| 10.0 | 8.0 | 19.0 | 5.0 | TX40 | 40 | 60~200 | Concrete only |
