. Hello everyone, today we will start our first

lecture on this course corrosion. This is a MOOC course a 20 hour course and ah 8 week

ah this course will be this course lectures should be floated. And I will be giving the

lecturers and in addition to that there will be three t s teaching assistants available

to respond to your queries as well as ah the problems what will be given to you, they will

be the first interface ah with whom you will be interacting for those solutions as well

as ah if you have any queries table respond and then of course, I will be also be available

all the time . This three t s are mister P K Rai mister N

K Prasad and mister B Bhushan and interestingly this all three t s are in their advance stage

of PSD and they are all doing in corrosion related topics .

Now, as I have mentioned in in my introduction that corrosion is a very very important subject.

And it is to be understood carefully and we need to spend little time on this and also

we mentioned that there are scientific aspects of corrosion, were electrochemistry is is

to be known is to be understood. But there are many engineering aspects to this materials

corrosion, where you would be seeing that many other factors like compositions of metals

and alloys ah design of components then environmental factors like oxygen concentrations and H 2

O presence; that means, moisture presence as well as sometimes you would see that the

stress also plays major role . We will go gradually one by one two different

aspects of corrosion , but today we will have a kind of ah history ah that why we should

study corrosion. And also you would find that ah there are some aspects which lead to kind

of catastrophe and if we do not understand corrosion properly, ah we would not be able

to protect our structures, which are made out of metals and alloys from corrosion and

finally, from premature failure . Now, ah before we got into the subject, I

would like to ah put up some of the corrosion books with are good books, and of course,

other books are available thousands of books are available, there are materials available

in internet you can Google anytime, and try to get as much as you want from the literature

as well as from internet . So, this books are just for reference, you

can find any other books because the aspects of corrosion is same whether you follow this

book or that book. It depends on how it is a presented in that particular book , but

still I have put some books. In addition to that you would find ah some of the lectures

in YouTube ah as well as ah as I mentioned that in this course we will also explain some

of the intricate matters related to corrosion. Now, coming to the subject directly. ah This

slide is actually if you see this slide this slide is ah related to some of those is basically

showing some the common features of corrosion. Now ah in day to day life, every direction

if you look at you would find examples of corrosion. I start with ah let us say ah our

utensils our a household goods, you will find that ah many a times ah household goods like

ah scrubber or kind of a this spatulas those are corroded heavily .

Even ah for example, the first picture if you see the first picture this picture if

you see, this picture is related to the corrosion of bolt, ok you see this entire part is so,

heavily corroded. This is the bolt part and this is the nut part nut is also corroded,

this is commonly observed feature . Now, another commonly observed feature is

ah if you consider ah overhead structures beams, this is the overhead structures and

beams ah they are also heavily corroded. And corrosion always it comes with the different

colour ah most of the cases and many a cases you do not find any signature of corrosion,

but still it happens and those cases are more deadly than ah any other cases, where you

have a kind of signature in the form of colour change .

Here you have ah the basically red rust which is forming, which is a typical feature of

iron corrosion. These are either a hydrated ferric oxide ah the ferrous ah ferrous of

ferric ions are containing over there, and this is this happens because of the presence

reaction with oxygen and moisture ah in the environment, this is basically a atmospheric

corrosion . Again if you see this kind of ah structure, which is a basically a kind

of beams as well as a kind of bridge also you will find this kind of corrosion .

If you can see that ah the entire material is out, ah and the kind of thickness what

it had this being physical initially it it was basically this much thickness and now

it has reduced this parti ah this particular section has reduced. That means, ah initially

it is to ah it it was designed ah to carry some load, now since the cross section has

reduced of course, it will not be able to follow that particular load it will not be

able to carry that load at some point of time it will definitely fail. And when this metallic

structure fails it fails catastrophically without giving any signal that it is failing

. Now, a typical ah corrosion features like

this, if you see this this is a kind of pipeline. ah I also ah relates to the ah safety safety

of ah people walking around that . Now, if it is a pipeline, now if it carries oil and

if suddenly this kind of failure happens, it might catch fire or any other things and

then it there could be explosions. Now kind of ah a failure here if you see, this is a

kind of pipeline which carries water. And then with the pipeline corrodes and finally,

it leaks ah before one could rectify and then finally, stop that leak ah you lose lot of

water. And of course, if you see this kind of situation,

where ah those corroded products even if the if it is carrying some kind of a liquid which

contains ah heavy metals and other stuffs like what we have in chemical factories. If

it leaks if that wall leaks it will leave that particular liquid into the ah environment

in the into the soil and that soil is contaminated ok ah.

For example ah if some sections some in if ah for example, in Kanpur specially, ah in

ah it is basically a belt where lot of ah ah this ah tanneries are there ok . So, the

tannery ah the this particular this particular ah kind of liquids, it it lead to the environment

those liquid contains lot of ah hm not so good metals . So, its also leads to environmental

hazards . So, ah this kind of corrosion ah we can see these are all ah visible ah naked

eyes . Now, if you consider this kind of corrosion,

which is basically related to a corrosion of ah tooth fooling. Tooth filling ah this

is also corroding, ah ah this is also not good ah if some metal is put up and then ah

if it goes out again it leads to a health hazard .

Now, this is a typical ah corrosion failure for example, in this zone, ah this is a kind

of broken bone which is ah locked which is connected by screwing and putting a rod. And

now if a this corrosion product is accumulating; and when this kind of attachment is fixed

to the bone to the broken bone finally, its function is to carry load. Now if there is

a corrosion product, it becomes weak now it will no longer hold the load and it will fail.

And when it fails, again if the person has to go and sleep on the operation table ok.

So, in other ah invasive surgery and a kind of trauma and other things other pains ah

those that person has to be here ah for another time .

So,. So, corrosion see these are actually some of the pictures are taken from internet

, but in the internet you just put this particular buzz word corrosion and damage or corrosion

accidents, you will find thousands of example .

Now, ah let me put up some ah small small examples like you might find in the ah though

it looks a little awkward, in the urinal you will find that a ah some ah kind of water

connections, there you will find that ah the top this nuts are little shiny , but ah the

base of that particular metal with the connector ah is corroded heavily. Now the question is

ah people always put nuts in the form of a kind of a better metal, which has little bit

of extra corrosion resistance. And that particular connector the small rod connector connects

this particular nut to the ah main pipeline source. Is of a a poorer great metal I would

say compared to that ah nut material ah . Now, this I am telling poorer great means

ah with reference to the corrosion resistance of those metals. Now that case a kind of corrosion

happens which is called galvanic corrosion, and there the connector which actually takes

water pipeline to the ah to the pipeline ah inside the ah bathroom ah that gets corroded

and leakage happens . So, this kind of stuff many a times happen in our day to day life

. And for example, another example I can sight

ah let us say ah water ah sink ah this ah kitchen sink. Kitchen sink sometimes we find

that ah at the corners we do get little bit of a kind of small small ah dots like ah appearance,

which are nothing, but pits and over the time this pit grows and then there is a leakage

. Another example ah water storage tank. Now

water storage tank the typical ah failure point is ah in the corner positions, at the

at the bottom corner you would find that leakage is taking place from there . So, that actually

relates to another kind of corrosion which is ah called crevice corrosion . So, those

everywhere you will find corrosion . Now, some of the cases you would see if some

construction is taking place. Sometimes people ah do construction and then they form the

beam and that beam is half cooked beam, I would say that half is made the half is ah

exposed; that means, all those reinforce birds are ah exposed to the environment. And you

would find that ah that beam during the rainy season that beam will become a kind of reddish

appearance, because that red rust what is forming on the expose reinforce spurs those

are trickle down and then it will make the beam colour reddish ok. This particular nature

is always ah visible ah if you look around Now, ah coming to your house, ah sometimes

ah if it is old house and if there is a problem of seepage. You would see after ah little

ah if you if you if you see a for a longer duration of time, the corners or say where

the seepage is more you would see that the cement is that particular concrete structure

as if its solemn ok and you will see the peel off of that particular a concrete ah ah pots.

And after sometime you might find that the reinforce bar is also exposed.

And the reinforce bar if you see carefully, ah its a kind of a flect reinforce bar the

reinforce bar if you see in the raw condition you will find that its nicely ripped a reinforce

bar ah with a little bit of red rust, but otherwise its fine. But over the time inside

the concrete that red rust is forming and that red rust has got a higher volume than

the metal so; that means, that particular concrete ah reinfore rebar, which call reinforce

bar the rebar is confined in the concrete structure .

So, when that corrosion is taking place in the rebar, its getting solemn because of that

rust formation and rust has got higher volume it gives huge pressure on the concrete. And

since concrete has got a very very small ah elongation, so, at some point of time concrete

starts cracking and then it falls off. And in fact, that makes the structure extremely

vulnerable to failure; even it happens in bridges old bridges you will find that some

places the ah rebar is exposed. ah Though it was initially confined in a concrete, but

over the time this concrete is getting spoiled off and then finally, the rebar is exposed

. So, those are kind of examples I am putting up .

So, these examples though you would not find that significant , but if we if we see some

of the data you will see that yes it is a significant and we need to see that how to

stop them. And in order to stop those we need to know how corrosion takes place . So, I

when I know the reason then we can attack some problem .

So, let us see a a kind of accidents that can that have taken place due to corrosion.

So, these data I am I have put ah Aloha incident Bhopal accident ah Carlsbad pipeline explosion

all sort of examples I am I I am putting . So, this you can also find out in this particular

website, its basically called corrosion doctors dot org, there you can get the history of

this particular ah failures there are other failures also , but here its nicely ah recorded

. Now, in those cases the accidents many a times

took life ok. Also ah if something breaks something fails for example, a silver bridge

1967, it broke down and there are lot of ah economy loss life loss finally, the connection

is lost and then again you have somebody has to rebuild it so, those cost needs to be considered.

And in fact, these particular failures all of though cases the corrosion is one of the

major causes major cause . Now, if I see some of the pictures) for example,

this picture this is a kind of oil vessel Erika, this failed due to corrosion. ah This

is a major reason ah that this failed this broke into half actually. Now this is ah the

kind of failure I was talking about this is a silver bridge silver bridge failure, ah

and ah I think ah its it happen in 1967. And again if you come to see this part this particular

situation, ah this is high temperature oxidation failure of aluminium steel heater tubes .

Now, here also since steel heater tubes, now here also since it is mentioned as oxidation

later you will see that oxidation is also a kind of corrosion ok . So, this kind of

failure I am just giving an example for sake of understanding that yes it can lead to a

serious accident . Now, a coming to cost ok ah we do see lot

of losses. For example, the USA its basically I could find 1998 data, it says that the cost

of corrosion means at the loss of money loss ah loss of money due to direct as well as

indirect ah loss. I will come to that direct as well as indirect loss 260 billion dollar

its not a small money, its 3.1 percent of ah g d p of that particular country .

Now, in India ah I have put two data, one is a ah this data which is 2012 data 2 lakh

crore ah rupees and this is in the form in in rupees. Then in 2016 data ok this is a

kind of a data what we have the 6 lakh crore so; that means, 2012 to 2016, ah we have for

the increase in loss of money due to corrosion is of the order of around ah 300 percent ok

its a quite a bit actually. Then its also the 4 to 5 percent GDP of a our country, which

is almost two trillion dollar economy . So, its a quite up quite a bit of loss .

Now, direct cost is basically us data infrastructure. Infrastructure when I am talking about direct

cost, this will be the failure of infrastructure bridge, buildings, utilities then transportation

of course, transportation railways. If you have noticed railways and also you can find

some of the pictures in the internet, that sometimes ah if you see the goods train ok.

In beach vizag I will show later some of the pictures in vizag sometimes a one picture

I have I will show it later . Ah One goods train ok was stranded for ah

almost two months there was waterfall. And that entire bogie was full of with water and

it was looking like a small swimming pool . So, now, you imagine, if it stays for longer

duration how much corrosion it can take place? And then finally, what happens you have to

throw that particular bogie and its a loss of money.

Then a production and manufacturing around 17.6 billion, government expenditure point

20.1 billion, total around 137.9 billion. Indirect cost is a kind of cost of labour

attributed a corrosion management activities. For example, ah let us say painting ok time

to time we have to paint the ah structures in the factory ok . So, for that you need

to spend money on paint, you need to spend money on the manpower because somebody is

to be there, to paint that particular structure . Then cost of equipment required because

the corrosion related activities ok. Of course, corrosion related for example, there is one

corrosion protection system which is called cathodic protection or anodic protection you

need to monitor ok instruments that how good is that particular corrosion protection . So,

that also needs money ah. Loss of revenue due to disruption in supply

of product for example, the bridge is broken. And once the bridge is broken then next at

least 2 3 months the supply chain is broken . So, its also loss of money of course, the

loss of cost of loss of reliability and it is not mentioned here, there is nothing important

other than life there will be life loss ok . So, this is a kind of data what I am showing

. So, we have to study corrosion . Now, coming to as we have mentioned about

all those losses, kind of accidents kind of examples, what we have put for till now that

there are corrosion incidents everywhere every direction. Now coming to material degradation,

material degradation something degrades and every structure everything what we have to

do with the material ah. Mechanisms of material degradation and the

characteristics of the economically significant forms of damage to the material are discussed

in terms of the physically and chemical process involved. Yes there will be physical features

there will be chemical process. For example, one particular example of physical features,

let us say ah ah a kind of a a structure we have built. Now if their for example, in a

stormy areas, where we have lot of storms. If there are sand particles and if that sand

particles hits any structure it will always erode its not corrosion, but it erodes ok

that is also a kind of loss of material is a material degradation .

Now, ah coming to railways ok in the railways ah there is one form of loss of material is

wear ok because wear happens when two bodies are in contact, and due to friction ah some

part of the material is lost ok. So, there will be a thickness reduction and finally,

you have to discard that particular product particular particular material, and you have

to replace that material with a new one . So, by direct mechanical action of course,

this wear; where you have ah kind of relative action a between two bodies and which are

in contact. Heat or radiation of course, heat does play a major role. Radiation of course,

for example, radiation damage one particular radiation damage is in nuclear applications.

Radiation does lead to a kind of a a loss of a material properties ok. We will come

to that it can lead to a a kind of void formation in materials. By [preseme/presence] presence

of chemical reagents yes there are chemical reactions there are electro chemical reactions

. Now, we would concentrate on electrochemical

reactions not chemical reactions of course, when we talk about electrochemical reactions,

we would also consider couple of things. ah For example, if we try to see iron corrosion,

and that iron corrosion you will see that iron is corroding in the form of electrochemical

reactions , but there there could be other aspects other reactions, which will be coming

along with that electrochemical reactions . So, our interest would be mainly in this

particular sections . Now, if we see all three by direct mechanical

action, by heat or radiation, by presence of chemical reagents, there could be combination

of two or more or all three could be present. For example, erosion corrosion, this is a

classic example of combination of all three . So, sometimes we for example, in heat exchanger.

Heat exchanger ah the hot air is being cooled by water ok . So, this water when it is flowing

it takes the heat . Now, when it flows, it could also lead to

erosion on the pipeline and at the same time this water also contains little bit of ah

chemicals which can lead to chemical attack on the surface in the form of chemical reaction

or electrochemical reaction so, there will be material loss . So, those kind of situation

for example, mechanical action and chemical reactions. Classic example is fritting action;

in the fritting also we have mechanical action as well as corrosion action ok .

So, this combination can also lead to material degradation fine . So, we would look at more

in a in a greater detail on this part electrochemical reactions or rather electro chemical degradation

which is nothing, but corrosion . So, as we understand till now that, first

of all we need to study corrosion and when you need to study corrosion we have to also

see the features of corrosion, we also need to see k the reasons of corrosion, we also

need to see how we can tackle corrosion . So, if we have all three combined then we can

become the successful corrosion engineer. Thank you .