The use of solid film lubricants with hard anodized aluminium

Abstract

SummaryThe nature of boundary lubrication is discussed and the characteristics of commercially available lubricants is reviewed. The mechanism of solid film lubrication is considered, with special reference to PTFE, molybdenum disulphide, graphite and allied systems. Typical properties of such lubricants are summarized, with reference to their coefficient of friction and stick-slip properties.Solid film lubricants can be categorized by the composition of the solid particles used, by the media in which they are dispersed and the type of binder used in the formulation. Some solid film lubricants are air drying and others require stoving to develop maximum thickness or adhesion. Examples of various types of such lubricants are given.Selection of suitable lubricants has to take into account the performance required in service, the nature of the substrate to be coated and the method of applying the lubricant. Because there are always conflicting requirements in such applications, the final choice is usually a compromise.The substrate mainly used with solid film lubricants is a hard anodized coating, but conventional protective anodizing or conversion coatings can also be used in less critical applications. The advantages and limitations of coatings applied to such substrates are discussed. The techniques of applying PTFE and molybdenum disulphide lubricants to hard anodic coatings are described and examples are given of applications of solid film lubricants to components used in the aerospace, high-technology and specialized engineering industries.