金属制件上的污物除动植物油外,还有矿物油类如石油及其衍生物、机油、石蜡、润滑油、沥青等。另有灰尘、切削物、磨料、研磨膏、切削液指坟盐迹等；对于固体油污,主要依靠表面活性剂对金属表面的浸湿和界面的吸附作用,改变固体颗粒油污与金属表面之间界面能,降低相互之间的引力，使之分离。对于液体油污，主要靠表面活性剂的渗透和乳化作用。液体油污在金属表面一般是铺展的薄层油膜,除油液渗透到表面与油膜之间,对油污浸湿乳化而脱落下来。因此除油是一个复杂过程，伴随了皂化、乳化、渗透、分散、溶解等多个作用过程的进行：

The dirt on the metal parts is removed from the vegetable oil, and there are mineral oils such as oil and its derivatives, oil, paraffin, lubricating oil, asphalt and so on. Otherwise, the dust cutting, abrasive, grinding paste, cutting fluid and other trace salt refers to the grave; for solid oil, mainly depends on the surfactant adsorption on metal wetting and interface surface, change of solid particles in oil and metal surface can reduce the force between the interface, leading to each other, to separate. For liquid oil, it depends mainly on the permeation and emulsification of surface active agent. Liquid oil pollution on the metal surface is generally spread thin layer of oil film, the oil is permeated between the surface and the oil film, and the emulsification of oil soaking and falling off. So oil removal is a complex process, accompanied by several processes, such as saponification, emulsification, penetration, dispersion and dissolution.