Although many spontaneous electrochemical processes have practical applications there is at least one which we would prefer did not occur at all: corrosion. Loosely defined, corrosion is the oxidation of a metal. Lots of resources are devoted to this problem every year but the inescapable reality remains: we live in a reactive atmosphere. Oxygen and metals generally combine readily--except for the "noble" metals like silver, gold, platinum, etc. Metal oxides are frequently less attractive and mechanically weaker than the original metals. And so we have a problem.
The laboratory experiment with
iron clearly reveals some factors which are important in the
corrosion process. Using the ferroxyl indicator system for
detecting Fe2+ ions, we can see that some
conditions seem to accelerate corrosion. 
.
The indicator system can help to discern the more subtle events during the corrosion of iron. First of all, water is an important factor in the corrosion of iron.
