Metal pretreatment processes have been used in manufacturing of goods for nearly a century.  Metal pretreatment is a key part of preparing surfaces to be coated using electrocoat paints.  The processes involve multiple steps including cleaning, pickling, surface conditioning, conversion coating and post treatment.  Iron phosphate and zinc phosphate are the two most common processes used in metal pretreatment.  The basic chemistry of these processes will be reviewed with a focus on paint adhesion and corrosion protection.