Atmospheric corrosion electrochemical cycle

The formation of 804 in the rust leads to the formation of corrosion cells at the rust Fe804 (sulfate nests) interface. Corrosion would continue to take place as long as the supply of 804 is abimdant [1]. A simplified diagram showing the contribution of an electrochemical cycle to atmospheric corrosion is shown in Fig. 10.8. The formation of Fe804 nests is illustrated in Fig. 10.9. To maintain corrosion, the corrosion cell requires an electronically conducting path which is provided by ferrous sulfate. Corrosion would slow down if the resistance of either of the paths is increased. 

Explain briefly the atmospheric corrosion of steel based on an electrochemical cycle. How is Fe(OH)2 converted to SO " and what is its effect on atmospheric corrosion ... 

Corrosion inhibitors The conditions that influence the onset of corrosion are the entrainment of atmospheric oxygen, moisture from the combustion of fuel, and stop-start running coupled with temperature cycling. In the marine diesel engine, the problem is exacerbated by contamination with fortuitous saline. Corrosion inhibitors are added specifically to cope with this electrochemical process. These additives operate by creating a physical barrier, in the form of a dense hydrophobic, monolayer of chemisorbed surfactant molecules, which prevent access of the water and oxygen to the metal surface. 

---