Many people believe that the main problem of the aluminum alloy electroplating process
is the plating adhesion problem; aluminum alloy
electroplated parts have various kinds and complicated structures; the plating adhesion problem will be very common to be seen in cavities and backs of aluminum die casts.
1. The reasons for the plating adhesion problem of aluminum alloy electroplating' pretreatment
(1) The cavity inner holes' internal diameters of aluminum alloy electroplated parts are too small and the holes are too deep; therefore, electroplated liquids and cleaning liquids can not flow and circulate well in workpieces, resulting in incomplete pretreatments of aluminum alloy parts' inner holes and poor adhesion or no adhesion of plating layers. There is interfacial tension at the included angle and the right angle which are at the end of the aluminum alloy electroplated part, resulting in these parts not to be cleaned; given this factor, the plating layer we obtain won't have good adhesion.
(2) Under the etching influence of the acid and alkali solution, the rough surface is not easy to be cleaned in the pretreatment process; the solution in the crack getting out will certainly affect the quality of the deep layer later when we electroplate the workpiece.
2. Improvement plans for aluminum alloy electroplating processes' pretreatments
We found that solutions in included angles and cracks of electroplating surfaces can be effectively treated based on repeated tests of aluminum alloy electroplating processes
. However, why does the problem occur so many times? The main reason is the incomplete water cleaning of the electroplated part's rough surface, included angle and crack in the pretreatment of the aluminum alloy electroplating process.
We have repeatedly tried a variety of water cleaning methods in order to solve cleaning problems in pretreatments of conventional aluminum alloy electroplating processes
. We add one ultrasonic cleaning process before the first zinc dipping process and another one before the second zinc dipping process under conditions of economy, efficiency and ensuring quality of electroplated layers.
The improved aluminum alloy electroplating process
is as the following.
The alkaline etching, the water cleaning, the pickling, the water cleaning, the ultrasonic cleaning, the zinc dipping, the water cleaning, the pickling, the water cleaning, the ultrasonic cleaning, the zinc dipping