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.