Metal must be clean to obtain good adherence of electroplate. Cleanliness of metals to be electroplated is of a higher order than that required for most other applications. Both oily matter and solid particles, which are particularly objectionable, must be removed. When present, oxide and scale must also be removed; the absence of gross quantities of these is assumed in this treatment. A common criterion of cleanliness is the absence of breaks in the water film remaining after rinsing. Observation is made after a short drainage period, for example, 30 sec. In addition to the high degree of cleanliness required, the necessity for maintaining brightness of buffed surfaces makes cleaning prior to electroplating most difficult and important. The electroplater can avoid poor plating, due to inadequate cleaning by cycles involving, in most cases: 1. Precleaning or solvent cleaning to remove the bulk of the soil. 2. Intermediate or alkaline cleaning, especially to remove oily matter. 3. Final electrocleaning, especially to remove the last traces of impacted solids and minor impurities. 4. Acid treatment and surface conditioning to remove small amounts of oxides formed during the cleaning process and to micro-etch the surface. While the division of steps is not always sharp, this permits discussion of these important stages in more detail. Surface conditioning, as by acid treatment, is not treated in detail because it is covered adequately in the ASTM Recommended Practices on preparation of specific metals for electroplating.