The Basics of Cleaning

摘要

What is cleaning? By Webster's definition "to clean" is to be free from dirt or to purify. In general, cleaning is the act of removing dirt, impurities or extraneous matter. Cleaning is actually a relative term depending on the type of soil that is being removed. In the food industry, cleaning requires the remo- val of any residue or organism that will cause spoilage. Likewise, in the medical industry, clean means sterilization of equipment and the environment. For the nuclear industry, clean means the absence of residual contaminants that is detrimental to the hardware of nuclear installations. Detrimental materials may include low melting point metals including mercury, halides, sulfur and other elements which may cause corrosion of different specialty alloys. In the industrial environment, particularly in metal working, cleaning means the removal of soils that will affect the processing of a part in the manufacturing chain. For example, a part that needs to be painted should be dry and free from oils to ensure paint adhesion and integrity of the coating after it has dried. Some parts, where there are no subsequent operations, cleaning may not be as critical and is only done to make the parts look presentable when shipped to customers. Before one can decide on how to go about cleaning a part, one must first understand what type of soil (or dirt or contaminant) is present on the part. Soils are classified into organic, inorganic or particulate. Organic soils are generally solvent soluble and are non-polar in nature. Examples of organic soils are oils, greases, rosins. On the other hand, inorganic soils are water-soluble and are polar. Examples of inorganic soils are salts found in plating baths and chlorides such as salts found in nature. Dirt that is neither soluble in solvent or water, normally is classified as particulate. Examples are grit, dust, metal or wood chips, etc. In almost all cases, all three types are present in any cleaning application, except that one is more predominant than others.