The difference of 316 stainless steel and 304 stainless steel for your railing system.
1. Corrosion Resistance
304 GRADE STAINLESS STEEL SECURITY SCREENS ARE VERY CORROSION RESISTANT
In coated mesh security applications there is little difference in corrosion resistance between 304 structural grade and 316 marine grade stainless steel.
Other brands use 316 marine grade stainless steel and claim to have higher resistance to corrosion, but the fact is for all products using high grade pre-treatment and high durability powder coat technologies, corrosion resistance levels are almost exactly the same in this application.
So that you can be assured - Crimsafe has been subjected to and has passed 3000 hours in the accelerated wet and dry cycling salt spray test which illustrates its excellent corrosion resistance.
AT A GIVEN STRENGTH 304 GRADE STAINLESS STEEL HAS A GREATER ABILITY TO DEFORM AND ABSORB ENERGY WITHOUT BREAKING THAN 316
Both 304 structural grade and 316 marine grade stainless steel in their softened state (annealed condition) are made to the same minimum Tensile Strength (strength before breaking) and Yield Strength (strength before permanently deforming.
Greater strength may be obtained from stainless steel by cold working the steel, for example, by bending or rolling a product, drawing wire from a thicker to a thinner diameter or hammering a product.
In the case of woven security wire, it is drawn from a larger diameter to a smaller diameter to obtain the correct tensile strength and yield strength.
At this stage 304 and 316 begin to behave differently:
- The rate at which 304 increases in strength is higher than the rate at which 316 increases in strength as it is drawn to smaller diameter.
- At a given strength, 304 also retains a higher level of ductility (the ability to absorb energy and deform without breaking),than 316.
In security applications this means 304 structural grade can remain stronger AND absorb more energy in an attack situation, than 316 marine grade.
This is an essential element in designing a security system.
3. What Does This All Mean When Selecting a Security Grade Product?
Much misinformation has been circulated regarding 304 structural grade stainless steel vs 316 marine grade stainless steel which has resulted in many people being misinformed about the true importance using 304 Structural grade stainless steel for security.
"We are not building boats" - Steve Brabeck (Crimsafe Managing Director)
Crimsafe uses a 0.9mm diameter 304 grade stainless steel wire which has been trademarked Tensile-Tuff®. Other mesh security systems use a 0.8mm diameter 316 grade wire. Crimsafe Tensile-Tuff 0.9mm 304 wire, when compared to 0.8mm 316 wire, has a 26.5% thicker cross- section. This means that at the same strength level, Tensile-Tuff can withstand loads at least 25% greater.
In addition, because of its lower rate of strengthening with cold work, 316 wire needs to be cold worked more than a 304 wire of the same diameter in order to gain its ability to be hard enough to pass the Australian Standard's Knife Shear Test. This greater level of cold work makes 316 product less ductile and less able to absorb energy and deform without breaking.
Weaving a mesh significantly deforms the wires and requires good ductility or, for the same ductility, a smaller wire diameter to avoid cracking or breakage. This balance of ductility/strength vs wire diameter is a design decision where Crimsafe have been able to make the larger diameter/ductility choice because of the properties of the selected 304 grade.
To better understand the significance of this difference in security applications - think of glass: glass is very hard and very strong, but it is also very brittle and breaks easily with sufficient force.
304 STAINLESS STEEL IS THE BEST FOR SECURITY APPLICATIONS
Crimsafe has found that 0.9mm diameter 304 structural grade stainless steel mesh performs better with higher ductility and higher energy absorption, at higher strength levels than 0.8mm diameter 316 marine grade making it more appropriate for use in security applications.
In security applications Crimsafe has chosen to use 304 grade Tensile-Tuff as we see no practical value or advantage in using 316 marine grade coated mesh over Crimsafe 304 grade Tensile-Tuff coated mesh.