So, the recording has started.

So let's start with what is corrosion?

So I think many of you have heard the word corrosion and have seen rust somewhere in

your life.

So corrosion, multiple people are trying to, these are textbook definitions.

So for example, the first definition by Danny Jones, he's saying it's a disruptive result

of a chemical reaction between a metal and environment.

What we mean is it can be a metal or an alloy.

So, and environment, it is not to be correct, it is not correct to say it is just a chemical

reaction.

Of course, it is a chemical reaction, but it is specifically an electrochemical reaction.

So another definition is that due to reaction, it can be anything.

So we want to, and as you can see, the definitions becoming broader and broader.

You can even say this environmental degradation of materials, not just metals, but in this

course, we will try to focus mainly on metallic materials.

So this field of corrosion lies at the intersection of electrochemistry and metallurgy.

So we need to understand, have a fundamental basic of both metallurgy and electrochemistry

to understand corrosion and try to tackle corrosion.

So there are several examples like from trivial examples to examples in critical application.

For example, you can see a cracking of a heat exchanger tube in a nuclear power plant can

be catastrophic, but a resting of an iron pipe lying somewhere might be just a trivial

example.

So, and we have, so one thing we need to note here is that the deterioration of materials

by physical causes such as light or just the temperature is not corrosion, but there

are other examples where you have some particles impinging, eroding the surface that is erosion,

gallium or wear that happens due to friction between two rubbing surfaces.

Those are not considered within the scope of corrosion.

So this is what is corrosion.

Then why do we care about corrosion?

I am going to give you four reasons why we should care about corrosion, starting from

cost, safety, and third is carbon footprint and fourth is materials conservation.

So cost of metallic erosion, you can see, if you see the global cost of corrosion every year,

it is around 2.2 trillion US dollars, which is almost 3 to 3.5 percent of the global GDP.

When you consider the value, it is very high and this includes only the direct cost due to

corrosion, not the indirect cost because some corrosion failures can lead to stoppage of work,

leads to loss of time.

Those are not accounted in this 2.2 trillion, so it is much more

highly can see the cost of downtime or the cost of material labor and maintenance.

These are not included in this 2.2 trillion.

That means the cost of corrosion is even higher.

If you want to read more about it, there is a white paper that is there

in the Strodon portal where you can see

there and there is also this damage to persons and environment that are not

taken care of. But hospitalization due to some corrosion failure is not accounted in this cost.

So it is a very costly endeavor. So we want to prevent corrosion because

it is really costly to do it. Sorry.

So then coming to the safety aspects of corrosion, that corrosion can have catastrophic

consequences. For example, these are boilers that are used in these power plants that use thermal

energy and convert it into electric energy. These pressure vessels and boilers can undergo

corrosion attack. Ships and submarines, obviously, as we will encounter a very obvious