Sacrificial Anodic Protection

Digital Assignment 1

By

Ritvik Khanna

15BIT0294

Note on:

Sacrificial Anodic Protection

The process of Corrosion is one of the major factors that lead to loss of money and material. Therefore, various steps should be taken in order to prevent the corrosion of metals.

The prevention of corrosion by the metal as a cathode in electrolytic cell is called Cathodic Protection. One of the methods of cathodic protection is Sacrificial Anodic Protection.

In this method, we use a more active metal than the metallic structure to be protected. The metallic structure is made cathode by connecting it to the more reactive metal used as anode. This would result in all the corrosion happening on the anodic region and the parent structure is thus protected.

It can be used to protect buried pipelines, underground cables and various other transportation systems from soil corrosion and water corrosion.

II. Calcium metal can be used to minimize Engine corrosion through this process.

III. To prevent the formation of rust in domestic water boilers by inserting magnesium sheets.

----------------------------------------------------------------------------------------------------------------------------------

Corrosion Inhibitors

The rate of corrosion can be easily reduced by the use of some chemicals. These chemicals are referred to as corrosion inhibitors. These include two types Anodic and Cathodic Inhibitors.

Anodic Inhibitors-

The chemicals which act on the anode and prevent anodic reactions are called as anodic inhibitors. They form sparingly soluble products which are eventually absorbed on the surface of the metal being protected and hence stop corrosion. For example Phosphate, chromate, tungsten which protect anode.

Cathodic Inhibitors-

The chemicals which act on the cathode and prevent cathodic reactions are known as cathodic inhibitors. Their mechanism is same as anodic inhibitors. For example organic amines, mercaptans, thiourea and substituted urea are examples of cathodic

The anode is usually a black fill composed of coke breeze or gypsum which would increase the electrical contact eith the surrounding soil.

This method can be applied to water cooler having open box, water tanks, marine piers, laid up ships etc. This kind of protection technique is particularly useful for larger structure unlike Sacrificial Anodic Protection, also for long term operations.

Being a quite useful process it has advantages as well as some limitations which restrict its use:

Advantages-

I. Replacement of anodes is not required as they are stable.

II. Well suited for large Structure with complex Shapes.

III. Suitable for long term operations.

IV. Even when the current requirement and the resistivity of the electrolytes are high this method can be used. Limitations-

I. Cost of investment is high.

II. External power is required