What are the factors that affect the rate of corrosion?

Assuming you're talking about iron, the signs of a chemical reaction are the following:

1) Color change

2) Temperature change

3) Formation of gas

4) Formation of a precipitate

As far as rusting goes, it definitely qualifies as color change. The factors of rusting are:

1) The Presence of Water

2) The amount of oxygen

3) The temprature around it

4) Electrolytes

5) The purity of the iron

In a nutshell:

If you add water, oxygen, and Gatorade plus leaving it at an outside temperature you're going to see rust.