Why do you use stainless materials in canyoning / caving?
Stainless steel, also called INOX, is an alloy of mainly iron, chromium, nickel and carbon. There are different types of stainless steel depending on the balance between these substances. The amount of chromium in the alloy is very important and determines the anti-corrosion properties of the stainless steel.
One of the biggest advantages of stainless steel is the fact that stainless steel is waterproof. This means that stainless steel is very resistant to the influences of water. The strength and protective properties of stainless steel are not easily affected by water, so we do not see corrosion quickly.
Advantages and disadvantages of stainless steel / INOX
advantages
- waterproof and therefore resistant to the influences of water
- resistant to weather influences
- increased resistance to acids and corrosion
- wear-resistant and therefore has a long life (sustainable)
- recyclable
cons
- more expensive than chromed steel or powder coated steel
- iron ore is not inexhaustible
What should you pay attention to / take into account
When the chromium comes into contact with oxygen, it forms an invisible layer of chromium oxide, which we call the oxide skin. This layer protects the underlying metal against further rust formation.
Stainless steel can still rust. The oxide skin is maintained by oxygen from the outside. If this layer is damaged, it will repair itself. If a damaged area is closed off from oxygen – for example due to the accumulation of dirt – the underlying metal will become active and start the rusting process.
Contamination of the surface of stainless steel can disrupt the formation of the protective oxide layer and thus adversely affect the corrosion resistance.
Some substantive background information
What exactly is stainless steel?
Numerous stainless steel alloys are available, each with their own specifications. The most commonly used stainless steel shapes are stainless steel 304 and stainless steel 316.
Stainless steel 304, also called the 18/8 alloy, 18 stands for 18% Cr (chrome) and 8 stands for 8% Ni (nickel). This offers good strength in relation to good formability of the material, making the alloy useful for many indoor and outdoor applications.
- Suitable for applications where weldability, polishability and very good deep drawing properties and wear resistance are required.
- The biggest 'weakness' of 304 is its sensitivity to chlorides and acids, which can cause (local) corrosion. More aggressive environments, such as seawater and coastal areas, may therefore be unsuitable for 304.
Stainless steel 316 also contains 2% molybdenum, which makes the material more resistant to crevice and stress corrosion and pitting corrosion. The molybdenum in the alloy makes 316 less sensitive to chlorides and acids. This in combination with a higher percentage of nickel increases the corrosion resistance.
These properties make 316 ideal for:
- moist environments with regular exposure to salt.
- is often recommended when aggressive environmental factors are involved.
The right alloy choice
Choosing the right stainless steel alloy determines the success of the application. An incorrect choice of alloy can cause the application to start rusting and therefore last a lot less. However, if you choose an alloy that is too highly alloyed than is necessary for the application, then you will be considerably more expensive in costs and you will pay for properties that you do not need. To choose the right alloy, factors such as environmental factors, surface finish and budget must be taken into account.
What exactly is stainless steel?
Numerous stainless steel alloys are available, each with their own specifications. The austenitic stainless steel or the AISI 300 series, represents the largest group of stainless steel types. This group is derived from 18/8 composition. The most commonly used stainless steel shapes are stainless steel 304 and stainless steel 316, both types are austenitic stainless steels. The material is non-magnetic, has good corrosion resistance, has a high coefficient of expansion and is a poor conductor of heat and electricity. Austenic stainless steel is of course attractive due to its high corrosion resistance and is therefore extremely suitable for applications in aggressive environmental factors. Although both types of stainless steel are austenitic types, the types do differ from each other. So when do you choose stainless steel 304 or stainless steel 316?
The differences between stainless steel 304 and 316
Stainless steel AISI 304, also called the 18/8 alloy, 18 stands for 18% Cr (chrome) and 8 stands for 8% Ni (nickel). This offers good strength in relation to good formability of the material, making the alloy useful for many indoor and outdoor applications. Suitable for applications where weldability, polishability and very good deep drawing properties and wear resistance are required. The biggest 'weakness' of 304 is its sensitivity to chlorides and acids, which can cause (local) corrosion. More aggressive environments, such as seawater and coastal areas, may therefore be unsuitable for 304
AISI 316 stainless steel also contains 2% molybdenum, which makes the material more resistant to crevice and stress corrosion and pitting corrosion. The molybdenum in the alloy makes 316 less sensitive to chlorides and acids. This in combination with a higher percentage of nickel increases the corrosion resistance of 316. These properties make 316 ideal for humid environments with regular exposure to salt. As a result, stainless steel 316 is often recommended when there are aggressive environmental factors. Note: For 316L, L stands for Low Carbon
Can 304 stainless steel only be used indoors?
In general, stainless steel 304 is usually used for indoors and stainless steel 316 for outdoor use. However, this rule certainly does not always apply. Stainless steel 304 can certainly also be used when an outdoor application does not have to deal with an aggressive environment and the risk of corrosion formation is less, such as in the case of e.g. screw foundations because it is not a problem that some flash rust is visible over time. The use of stainless steel 304 in screw foundations makes a considerable difference in costs and still gives the same desired result.
Is galvanized steel stainless?
What is the difference between galvanized steel and stainless steel?
Galvanized steel steel has a coating of zinc on the metal's surface. The zinc layer builds up an oxide layer that prevents further corrosion.
Stainless steel has a certain amount of nickel and/or chromium added to the steel alloy.
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