A slightly different, perhaps more obscure topic for my monthly statement this month, but I’m on the path of bringing environmental awareness to the fore, and this subject seemed as equally important as any other.
So this month, I’m discussing Stainless Steel, how it decomposes, the decomposing process and its effects on the environment.
But first, here’s the quick answer, then we’ll dive into more details…
Does Stainless Steel Decompose? Stainless steel can decompose. But the decomposing process is reduced greatly by its chromium oxide “Cr203” layer (Protective layer). It also has a “self-healing” effect, where new protective layers are formed when destroyed. Sodium chloride (salt) increases the breakdown of stainless steel.
Stainless steel is used for lots of things, from stainless utensils that go through many years of use and remains shiny, to vehicle components and even in sea going vessels – . But does it decompose at all? Let’s address this question first.
Does stainless steel decompose?
As I mentioned, stainless steel does decompose, but the process and effects of this decomposing can be pretty minimal because of several factors.
Stainless steel, by its very nature, has several special characteristics and processes that it goes through to limit the effects of rust and decomposition.
So the circumstances in which stainless steel will decompose is based largely on the environment and from its own characteristics.
Firstly, stainless steel doesn’t decompose easily because it has the component chromium – which is very reactive.
So when stainless steel is exposed to oxygen, the chromium forms a thin layer called chromium oxide (Cr203) on the surfaces that are exposed to oxygen.
This special layer that forms when exposed to oxygen is extremely sturdy and prevents oxygen from entering the steel beneath.
So unless this layer is disturbed, through scratching or even chemical exposure, the stainless steel wouldn’t decompose for a very long time.
One of the common chemical components that disturbs this protective layer is chlorine. So because of this, stainless steel is easily attacked by any chlorine based compound.
One of the most common forms of this destructive component is sodium chloride (table salt).
So for example, when a fork or any other small utensil is thrown into the ocean which obviously contains saltwater, in this environment stainless steel can decompose relatively quickly.
This happens because the protective layer is destroyed quicker by salt content in the liquid, or even present in air particles, and therefore speeds up the corrosion process.
Here, I would lean heavily on the term “relative”, as the level of corrosion largely depends on the the salt concentration in the water.
Where there’s a mild concentration of salt in ocean water, stainless steel could last for decades, gradually decomposing.
Usually, the thinner areas of the steel will decompose first, followed by the thicker areas.
For example, if it’s a stainless steel fork, the forks would decompose faster than the relatively thicker handle.
The effect of this decomposition would differ in other environments.
Using the example of a jungle or forest, if the stainless steel is simply discarded on the surface, the in one of these environments, it would probably become buried over a period of time.
Once buried, and with minimal interaction with destroying components like sodium chloride, such stainless steel could potentially last forever without corroding.
But again, sometimes the groundwater and the different chemicals and minerals in it can affect this decomposability
How long does stainless steel last
When answering the question does stainless steel decompose, the answer is yes, But as you might have guessed through the above explanation, there’s no exact measurement as to how long stainless steel can take to.
This is because it depends on the environment and the chemicals and elements that stainless steel becomes exposed to.
Sometimes even the grades of the stainless steel matter in judging how long it will last.
For example, stainless steel with a grade 316 is believed to last as long as 1200 years with minimal disturbances to its protective layer … that’s a long time!
It’s well known that some stainless steel utensils produced and used as far back as the 1970s still maintain their excellent shape to date.
The main aspects that can affect how long stainless steel can last are as follows,
- The alloy composition of steel
- Chemical Submersions
Stainless steel decomposing process
To make matters simple the corrosion aspect, and all the processes that stainless steel goes through to decompose can be compared to a healthy apple.
An apple can stay edible for a long time because of its peel. Astonishingly, an apple peel less than a tenth of a millimeter thick can protect the apple.
It’s only this outer peel that avoids any substances entering or escaping from the apple, to keep it edible for longer.
Assume if a worm has eaten up half of the apple, disturbing the layer the peel has formed. This would then compromise the protective seal and trigger the rotting process for the apple making it inedible.
It doesn’t matter how this seal is compromised, if an apple is cut in half, it would also oxidize the apple quickly making it easier for it to decompose.
Similarly, even if thinner than an apple peel, the protective layer of stainless steel protects the steel from decomposing. So no foreign substances can enter nor can the ions in the metals escape from the metal easily.
The biggest difference between an apple and stainless steel is the ability of the steel to repair from its disturbed oxide layer by itself.
Meaning an apple cannot regain its peel back to stop an apple from rotting. In contrast, when the chromium oxide layer (the protective layer of steel) is damaged, oxygen helps in forming a new fresh layer spontaneously.
This effect is known as the “Self-healing effect”. But again it has to be stated that the presence or interactions of sodium chloride can badly disturb or even reduce this healing effect.
Stainless steel effects on the environment
The good news is that stainless steel is 100% recyclable. Stainless steel is not coated with any toxic chemical formula or environmentally harmful substances in any of its layers and so there’s no possible toxic danger to the environment.
If stainless steel is not recycled and does not end up at any of the disposal site options, it should still not adversely affect the soil or underground water supply.
So becuase of this, many companies make use of this material over and above other non-recyclable materials.
When producing stainless steel, scrap metal is one of the primary raw materials.
Scrap metal comes mostly from recycled materials and makes up to 70% of stainless steel manufacture.
And these days, advanced technology also supports reducing the energy needed to make stainless steel.
So with the additional bonus of recycling in order to produce stainless steel! there’s further minimal environmental effect from the stainless steel manufacturing process.
Why am I focussing on this as a monthly statement? For me it’s not just looking at and tackling the news-worthy aspects of the environmental, but a multi-faceted approach to everything that can affect the environment, even if … in the case of stainless steel, we find that actually we are ok to produce it and use it without adverse effects.
It’s about looking at everything, and the whole picture, and that includes the smaller subjects too.
If you want to help towards good causes, why not consider donating to the Rutakirwa Foundation, where, with your help, we seek to build a better world for everyone.
Till next month,
I remain truly yours,
Serving since 28th December 2008.