Corrosion Case Study

Corrosion accidents:- Bhopal tragedy

Corrosion and its types:

A BASIC QUESTION

What is Corrosion ????

DEFINATION:

Corrosion is a natural process, which converts refined metal to their more stable oxide. It is the gradual destruction of materials (usually metals) by chemical reaction with their environment. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen.

Corrosion is the phenomenon of a metal or an alloy to undergo destruction or degradation by its interaction with the surrounding environment. Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated

This selective leaching of an alloying element from the surface can result in the surface becoming dealloyed and in some cases this dealloying of metal is not limited to the surface and it grows in to the solid causing a serious loss in mechanical strength of the metal or alloy.

6: ENVIRONMENTALLY INDUCED FRACTURE: Application of mechanical stress to a metal or alloy when it is exposed to a chemically reactive environment results in formation and propagation of cracks at points of stresses below those required for cracking by purely mechanical process in absence of corrosive environment.

7: GALVANIC: Because different elements in alloy or metal has different chemical activities, therefore they have different electrochemical properties. When dissimilar metals join in such a way there electrical circuit gets completed due to unfamiliar environment and thus results in corrosion of metal.

8: EROSION: Mixing or stirring of solution can accelerate the rate of corrosion either by increasing the rate of transport to the surface or by mechanically damaging or removing surface films that protect the underlying metal from

All three tanks were in use. It is expected that one tank will be kept free for emergency purposes. In the United States, Japan, and Germany, MIC was either used up as it was produced or stored only for brief periods and never in such huge quantities as in Bhopal. Tank 610 had 6.4 tons of MIC prior to October 7 to which was added MIC produced from October 7 til October 22. Thus MIC was not only kept for 55 days, but Tank 610 contained two separate pools of MIC. It is expected that tanks should be no more than half full; however, prior to the fateful night in Bhopal, the Tank 610 was 87% full, which is far above the recommended capacity of 50% at the West Virginia plant and the 60% specification for the Bhopal plant Tanks containing MIC are required to be kept under refrigeration; this elementary caution was violated at

Bhopal. The Union Carbide manual specifies that the alarm should respond whenever the temperature goes above 11°C; in Bhopal it was set at 20°C. Most evidence suggests that MIC in the Bhopal plant was generally at or above 15°C.

Causes for Bhopal disaster

The main reason behind the Bhopal disaster was the gas