Aqueous Lubrication

Generally, whenever we think of lubrication, it is oil which strikes us. Today, almost 1% of total mineral oil consumed in the world is used as a lubricant in some form or other. Oil-in-water emulsion is used as a lubricant for many metalworking processes. But here also, oil is mainly responsible for controlling friction. There are few specific applications where only water-based lubricants are used. For example, in the mining industry, oil-free water-based lubricants are used to lubricate pumps because flammability of oil is dangerous in this application. This is, however, a relatively special application in the world of lubricated contacts, and besides this, oil-free, water-based lubricants are used very scarcely. There are some properties of water which make it a potential candidate as lubricant: readily available, non-toxic, environmentally friendly and has high heat capacity which gives it excellent heat transfer properties. At the same time, there are some properties of water which are disadvantageous: low boiling point and low high-pressure viscosity index which result in poor load-carrying capacity. The current chapter will discuss different ways to employ water as an effective lubricant in different tribological applications.