A MAJOR FACTOR determining the performance of a phosphate conversion coating is the cleanliness of the surface being treated. This paper presents a brief overview of cleaning and describes the effect of various alkaline cleaner components on subsequent zinc phosphate conversion coating of zinc and aluminum surfaces. Effects caused by the reaction of these components due to cleaner aging are also discussed. Evidence is presented to show that reduced silicate cleaners produce good phosphate crystal morphology over the life of the cleaner bath while maintaining low metal etch of the surface being cleaned. For the surfaces examined, this cleaner type is preferred over the highly silicated cleaners.