 My name is Mahirubalai, I am assistant engineer in WIT, Swalapur. We are talking about a corrosion control in the metal pipes today. So what are the learning outcomes? Students will be able to understand various methods of corrosion control in the metal pipes. So let's see the different methods for corrosion control. There are totally four types of corrosion control methods. The first one is cathodic protection, where we convert the metal pipe into the cathode. Second one is protective cold coatings and linings. We protect the interior pipe perimeter by giving out coating or lining into it. Third one is selecting proper pipe material. It means if you don't want to put a lot of money for coating and linings, we can change the material, okay? We can put some initial cost to it and we can change the pipe material in such a way that the pipe material will not rust very much at a faster rate. The last one, last one is the quality of water. How we can treat the water or how we can make the water so that the corrosion rate can decrease, okay? So let's see cathodic protection first, right? Here this is our metal pipe through which the water is continuously flowing. Here you can see this metal pipe outer is connected to a metal. Here I had taken magnesium. You can take a different metal, but you have to understand which material we have to take. We have to take the material in such a way that higher electrochemical series material. What does it mean? It means that it can give out electrons faster than this metal pipe, okay? Then what will happen? When we connect these both metals, what will happen? As it is giving out electrons at a faster rate, it will try to throw out electron towards this metal pipe. As you had seen in the corrosion process, this metal pipe is behaving as anode. Now it is receiving cathode at outer parameter, okay? What does it mean? It is shifted towards cathode. What will happen after that, okay? At that time, the inner parameter or the electron which is flowing through the metal in the corrosion process, it will take an out, okay? And it will be reacting with the soil which is present outside the pipe. How it is going to happen? What is its chemistry on which we can say that, yes, it is going under the cathodic protection? Before that, you have to understand what is happening with this metal. Here in the MG, the MG2 plus is dissociated and the electron is taken out from this wire and this MG2 plus is given out in the soil, okay? And all the soil materials, all the soil anions, what I can say, which is negative charge, it is attracted towards the metal and it is reacting with the MG2 plus, okay? Automatically, it is becoming stable or its nearby area is becoming stable. So what I can say? I can say the MG is dissociated into MG2 plus and two electron minus, okay? At this side, what is happening at this side? At this side, whatever the oxygen which is present, which is present in the underground soil, that is our oxygen, okay? And the water which is present outside in the underground soil. I'm not talking about the inside water flow rate. I'm talking about the water which is present outside which in the underground soil. It will try to capture the electron which is coming from this wire and it will form four OH minus outside the pipe on the perimeter. So what will happen to that? This OH minus will try to form the negative charge on the pipe. It means it will try to shift all the anodic sides to cathodic sides. So what we can say? It will try to decrease the corrosion process. I'm not saying it is gonna stop the corrosion process. I'm saying that as relatively cathodic sides are too much and anodic sides are very much lesser and electron is not shifting towards in interior cathodic side, but it is shifting towards outward cathodic side. So automatically inside corrosion is going to stop. There are chances that this outer perimeter can get corrode, but the chances are very much less and it doesn't involve and it will not get in contact with the interior pipe. So the design flow will not change. The pressure head will not create and automatically we will get the effective water flow into it and water which we had designed and it's quality will not change too much, okay? So what is the next one? Next one is protective coating and lining. So there are different type of coatings and linings which are present in the market. Let's see the first one. Basically in the paints we use mostly red lead paints and zinc pigment, okay? These zinc pigments and red lead pigments are basically lower electroseries metals. So they are not gonna rest very much faster. Second one is galvanization. In the galvanization basically we do for very small diameter pipes, okay? How we can do that? We put a pipe into a molten zinc, okay? So that all the surface area will be very much precisely get covered with the zinc belt, okay? It is mostly expensive. So we don't go for such kind of a galvanization, okay? The third one is the bituminous compound coatings in which we use bituminous for the coating of pipes, okay? So it is mostly done for conveying system or what we can say large pipes, okay? For the large pipes. If you see in this diagram it is the outer parameter is coated with the bituminous. And the fourth one is cement linings. We use cement for the coating of interior pipes in which we mostly use one rest or two cement motor, okay? It is also mostly done for conveying system pipes. If you see in this diagram you can understand the interior pipe is coated with the cement linings, okay? The third one is metal pipe. If you don't want to go for the coatings or linings we can change the pipe material, okay? So there are mostly focus on homogeneity of pipe material because we can't use a lot of LOIs which are not homogeneous in nature. So we always go for the homogeneity of pipe material in which there are two types, okay? It is less resistant to corrosion and more resistant to corrosion. In the less resistant we typically go for iron which is in the form of steel, okay? It is mostly used in the distribution system in the cities, okay? In the more resistant we typically go for iron or steel with chromium, copper or nickel. Copper or nickel we can preferably choose with respect to our cost. We mostly use copper for the alloy, okay? So evader is also one example we typically use in the conveying system. Evader is the alloy of copper and silicon. It is lesser expensive. We can mostly go for the evader in the conveying system. Here is the example of steel, alloy of steel and copper. You can see it is not a rust, okay? It is its color and here it is a stainless steel pipe. It is mostly a low iron steel alloy, fine? So it is mostly used in the distribution system and the alloy of steel and copper is mostly used in the conveying system. And the fourth one is quality of water. As the water is containing higher carbon dioxide or the water is too much alkaline or the water is too much higher dissolved oxygen. At that time what will happen? The corrosion process requires oxygen, okay? The corrosion process requires a lot of water with having a capacity to take up a lot of metal ions. At that time the corrosion rate will go on faster. So we have to change the quality of water so that the corrosion process can decrease in their rate. So how we can do that? We can increase the pH. What will happen? It will try to increase the alkalinity. Here you have to understand. We are using lime or copper or powdered chalk. It means we are using CAO or CAOH twice. Okay, what will happen at that time? We are increasing only OH minus, okay? We are not increasing carbonates and bicarbonates. The raising pH means only increasing OH minus ions. It will not gonna affect the corrosion process. It will decrease the rate of corrosion, okay? We can also do it by reducing the dissolved oxygen content, okay? By idiom, sodium, exam at a phosphate. It is having a proper dose of 0.5 ppm to 0.6 ppm. We can decrease the oxygen content of water. What will happen after that? It will try to decrease the rate of corrosion, okay? And the third one is reducing the dissolved carbon dioxide. By decreasing the dissolved carbon dioxide, it is basically the calcium carbonate can be controlled. It means when we decrease the carbon dioxide, automatically the ferrous bicarbonate will not form. After that, ferric hydroxide will not form. So by decreasing the dissolved carbon dioxide, we can stop the corrosion process at a very rapid rate, okay? It is also done by adding sodium metaphosphate. So let's see some review questions. The first one is corrosion of steel is controlled by addition of lime, true or false. Second one is corrosion control is cheap in, selection of pipe material, changing quality of water, cathodic protection, protective coating. Third one is protection of stainless steel from the corrosion required, cathodic protection, changing of quality of water, protective coating, or none of the above. So these are the answers for that. The corrosion is mostly controlled by addition of lime. Yes, it is always true. Corrosion control is cheap in only protective coating, okay? In the protection of stainless steel from corrosion required, none of the above, okay? Because stainless steel is basically alloy. And if you are changing the above three processes, we can't do that, okay? So we must go for a proper higher grade stainless steel. These are the references I have studied for making this PPPT. Thank you.