This SAE Aerospace Recommended Practice (ARP) describes a method for classifying the frequencies of analysis of solutions used in the processing of metals, such as electroplating, anodizing, and conversion coating and associated processes but usage is not limited to such applications. This document is intended to establish a periodic test plan that may be used by processors to satisfy the requirement of an Aerospace Material Specification (AMS) for a chemical processing solution periodic test plan as a control factor. This document does not fulfill the criteria for a formal statistical process control program.