Cold Forming Aluminium Alloys — Development of a Control System for a Phosphate Lubrication Process

The zinc phosphate-sodium stearate method of lubrication is used extensively for the cold forming of steel. The control of the chemical composition of the solution used in this process is relatively simple and poses few problems for industry. However, a similar lubrication process which is often used when the higher strength aluminium alloys are cold formed has been found to be most difficult and costly to control in many industrial applications. A series of planned experiments were made on a pilot plant of a zinc phosphate-sodium stearate process for aluminium. The object of this paper is to describe the behaviour of certain “control” chemical characteristics of the phosphating solution in the process as an increasing amount of an aluminium alloy is passed through the solution. From these results a control plan for the solution is developed together with chemical replenishment procedures for maintaining the solution in “control” under continuous operating conditions that are normally experienced in industry.