The difference between Defender® 304 Grade & 316 Grade Stainless Steel Bird Spikes

Defender Bird Spikes - 304 and 316 grade stainless steel

Our Defender® stainless steel bird spikes are available in both 304 and 316 grade stainless steel so we are often asked what the difference is between these grades. It can be hard to explain the pros and cons of each so we have put together a definitive answer for you, but do bear with us while we go right back to basics.

What is Steel?

Steel is an alloy made of carbon and iron which has good strength and fracture properties when compared to iron on its own.

What is Stainless Steel?

Adding a minimum of 10% chromium to low-carbon steel is what creates stainless steel. The chromium oxidises in oxygen to create a rough, thin, invisible film on the surface which in turn creates a barrier against corrosion and additional oxidisation, it can also self-heal if damaged either mechanically or chemically! Magic!

Different grades of stainless steel have various degrees of strength, corrosion resistance, high and low-temperature performance, hardness, ductility (ability to be stretched or drawn into a thin wire) and wear. The microstructure (the way molecules are bonded together and can only seen under a microscope) is what impacts its grade and mechanical properties. There are 5 types of steel microstructure; ferrite, pearlite, martensite, cementite and austenite.

What is corrosion?

When iron combines with oxygen and water, a flaky red oxide forms, commonly known as rust. Steel and iron are both susceptible to this type of corrosion particularly with in coastal areas where sodium chloride is present in the air. Pitting is a localised type of corrosion that creates shallow holes or crevices on the surface.

What type of steel is used in Defender® Bird Spike manufacture?

We use austenitic stainless steel 300 series for our bird spikes, it’s the commonest class. It is characterised by microstructure which is a cubic structure. The two types of stainless steel we manufacture our spikes in are type 304 and type 316. These types are non-magnetic, can be hardened through cold-working, (not heat treatment) and because of the added chromium and nickel, they have super corrosion-resistant properties.

Comparing 304-grade and 316-grade stainless steel

Type 304

Also known as 304 Grade, it is the most common and versatile austenitic stainless steel. As it has high levels of chromium and nickel it has excellent corrosion resistance, strength and fabric-ability. Its particular resistance to the atmosphere and pollutants makes it ideal for outside applications, for example in bird spikes! It also has excellent heat resistance. 304 grade is a ductile metal meaning good machinability properties and can be formed into complex shapes and sizes without losing strength. Ideal for bird spike pins.

Type 316

Also known as 316 Marine Grade, it is the second most commonly used stainless steel after 304. Alongside the chromium, this grade has higher levels of nickel than 304 and added molybdenum. This is the perfect combo to provide increased corrosion resistance. The molybdenum specifically controls pit-type corrosion which exposure to sodium chloride (salt) phosphoric and acetic acids causes. It is often referred to as marine grade due to its suitability for use in saltwater environments. Molybdenum is an extremely hard element that increases the toughness and strength of 316 which gives it super heat and wear resistance.

The addition of other alloys further enhances its resistance properties. Its austenitic microstructure retains toughness over a wide range of temperatures. This is why it is used in highly corrosive environments such as chemical plants and marine coastal areas.

Comparison Chart of Elements for 304 Stainless Steel and 316 Stainless Steel

Alloy % of 304 % of 316 Description
Carbon: 0.08 0.08 Adds strength and hardness. Iron on its own has poor mechanical properties
Manganese: 2.0 2.0 Used to decrease amount of nickel needed
Phosphorus: 0.045 0.045 A residue from the manufacture of carbon steel
Sulphur: 0.03 0.03 Improves machinability
Silicon: 1.0 1.0 A deoxidiser. Improves strength
Chromium: 18-20 16-18 Addition makes carbon steel into stainless steel
Nickel: 8-10.5 10-14 Retains austenitic microstructure giving corrosion resistance
Molybdenum: 0 2-3 Maintains toughness. Increases resistance to pitting corrosion
Defender Bird Spikes - 304 and 316 grade stainless steel wires ready for assembling

What other metal can bird spikes be made from?

There are 2 sub groups of austenitic stainless steel, the 200 series and the 300 series. Each are suited to different applications due to the added alloys. The 200 series has limited applications due to the low nickel content substituted by nitrogen, while 300 has higher levels of nickel which significantly gives superior corrosion resistance compared to other grades. Many of the added alloys make the 200 series and some of the 300 series unsuitable for use in bird spike manufacture; 303 grade has great machinability but reduced corrosion resistance, 310 and 347 grades are great for welding and high temperatures, often used in furnace components and 321 is best for parts that need good weldability.

Some bird spikes can be manufactured from galvanised steel. This is a carbon steel that has been galvanised or coated in zinc. Zinc acts as a barrier preventing oxygen and water reaching the steel and causing corrosion. However, this coating is not self healing like chromium, it can scratch off and be damaged so eventually galvanised steel will rust. It also lacks resistance to sodium chloride, so using it in coastal areas is a no.

Galvanised steel is not as strong as stainless steel. It lacks the strength-giving added alloys of stainless steel. This also means that spikes made from galvanised will tend to bend, losing shape and effectiveness.


All stainless steel Defender® Bird Spikes are manufactured here in the UK from 304-grade stainless steel as standard. We are so confident in this grade that all our stainless steel spikes come with a 25-year ‘No Rust’ warranty when installed correctly in the UK. However, should bird spikes be needed in coastal areas or areas of high pollution, we would recommend using 316 Grade. We have found that increasingly, architects and project managers are requesting that bird spike installations use 316-grade steel. All our Defender® stainless steel pigeon and seagull spikes are available to purchase with pins made with 316. They are, however, not made as standard and we require 24 hours' notice for our assemblers to make the spikes for you.

If you would like more information on our 316-grade bird spikes, do give us a call on 01626 835055 or drop us an email on

We have placed cookies on your device to help make this website better. Please view our Cookie Policy for more details.

Your Basket