Since we are going to be talking about cleaning, or, more specifically, industrial parts cleaning, it’s probably best that we define what we mean by “cleaning.” The term is used quite loosely to define a variety of process not all of which are really “cleaning.” “Cleaning” is the removal of the stuff that we usually call “dirt.” It may consist of solid or liquid constituents clinging to the surface of the part by simple adhesion. The “dirt” is easily identified from the substrate and is its own separate entity. Cleaning to remove dirt does nothing to change the surface of the part leaving it just as it was but without the dirt. Cleaning a part to remove oil and machining chips is a good example of parts cleaning. All other “cleaning” processes are technically “surface treatment.” These processes may be chemical or mechanical in nature and alter the surface of the part being cleaned in one way or another but without significantly changing the remaining substrate. The removal of surface oxides prior to plating is a good example of surface treatment. Finally, there are “cleaning” processes which significantly alter the part substrate. These include such things as etching and surface abrasion. Although these processes are often called “pretreatment” they tend to be categorized along with cleaning. Although all of the above are commonly called “cleaning” they are distinctly different. Each has a different purpose and is applied with different equipment and a different set of rules. It really isn’t possible to discuss “cleaning” without the other, related, processes popping up along the way. It is important that we know, however, that “cleaning” is not an absolute term.