When choosing stainless steel fasteners and timber connectors, two of the most common grades you will come across are AISI 304 (A2) and AISI 316 (A4).
Both are stainless steels with good corrosion resistance, but AISI 304 (A2) and AISI 316 (A4) are designed for different levels of environmental exposure.
AISI 304 (A2) – the standard choice
AISI 304, also known as A2 stainless steel, is one of the most widely used stainless steel grades.
It offers a good combination of corrosion resistance, performance and cost, making AISI 304 (A2) suitable for a wide range of construction and outdoor applications.
AISI 304 (A2) is commonly used for:
- timber construction
- terraces and outdoor structures
- general construction
- fasteners and timber connectors
- areas with normal humidity and weather exposure
For many inland applications, AISI 304 (A2) provides sufficient corrosion resistance without the additional cost of AISI 316 (A4).
AISI 316 (A4) – for more demanding environments
AISI 316, also known as A4 stainless steel, provides a higher level of corrosion resistance than AISI 304 (A2).
The key difference is its improved resistance to chlorides, salt and moisture, making AISI 316 (A4) particularly suitable for more demanding environments.
AISI 316 (A4) is commonly preferred for:
- coastal and marine environments
- areas with high salt exposure
- swimming pools
- chemically aggressive environments
- applications where higher corrosion resistance is required
A simple rule of thumb
AISI 304 (A2) = standard stainless steel and a strong price-to-performance choice.
AISI 316 (A4) = higher corrosion resistance for more demanding environments.
When selecting stainless steel timber connectors such as joist hangers, angle brackets and rafter connectors, the correct grade depends on the actual exposure conditions and project requirements.
As a general rule, AISI 316 (A4) is commonly preferred in coastal areas and more aggressive C4–C5 corrosion environments, while AISI 304 (A2) is often sufficient for many inland applications.
The “better” stainless steel isn’t always the right one. The key is choosing the right material for the environment and application.
Our product range includes a variety of stainless steel timber connectors, including solutions made from AISI 304 (A2)and AISI 316 (A4) stainless steel.