There is a growing need for non-zinc ashless hydraulic fluids for industrial and mobile applications. Zinc has been used historically to provide good antiwear protection as well as adding oxidation stability to the finished product. Zinc is becoming a concern because it is a heavy metal which is undesirable for a number of reasons including environmental aspects. The most common non-zinc hydraulic fluids available today are mineral oil, vegetable oil, and synthetic esters.
The vegetable oil base fluid is considered to be readily biodegradable and some are non-toxic. This product has application for environmentally sensitive industries such as Agriculture, Construction, Mining, Forestry, and Commercial Fishing. Both non-zinc mineral and vegetable based antiwear fluids are more commonly used in Europe at the present time, but their use in the United States is rapidly expanding.
The purpose of this paper is to review the present, and future non-zinc hydraulic fluid technologies covering performance as well as environmental aspects.