The Aluminum Plating Process

Aluminum Plating

The most common method for making plated metals is a process called electroplating, where an electric current is passed though a solution containing metal salts and the metal which is to be plated, resulting in the deposition of a thin layer of a metal such as gold, copper or aluminum on the surface of another metal. Electroplating has many applications in industry, for example aluminum plated metal is protected from corrosion due to aluminum's high resistance to unwanted chemical reactions. As aluminum itself is quite expensive, electroplating it onto cheaper materials allows economical and corrosion-resistant plated metal

The Electrolytic Cell

To understand the electroplating process, a basic understanding of the electrolytic cell is necessary. An electrolytic cell is a type of electrical circuit comprised of two half-cells. In each half cell there is an electrode made out of a specific metal, and an electrolyte solution containing that same metal as an ion. An example of this in an actual voltaic cell would be electrodes made of zinc and copper and electrolytic solutions of zinc sulfate and copper sulfate. Because zinc and copper sulfate separate to form a charged metal ion and a sulfate ion in water, they conduct transmit an electric current.
The two electrodes of the cell are referred to as the anode and the cathode, and are negatively and positively charged, respectively. Current flows from the anode to the cathode, utilizing the electrolytic solution as a conductor. Please note that this is by no means an in-depth explanation of electrolytic cells, but rather is an explanation of the background information necessary to understand electroplating.

Electroplating

An electrolytic circuit is set up, with the metal to be plated as the cathode of the cell and the plating metal as the anode. Both electrodes are immersed in an electrolytic solution containing salts from both metals, and possibly several other ionic compounds. The cathode is connected to the negative terminal of a battery or other source of direct current, whereas the anode is connected to the positive terminal.
Once current is run through the cell, atoms in the anode, which in this case is made from aluminum, gain a positive charge. Once an atom of aluminum gains a charge it becomes an ion and can no longer subside in a cluster of neutral atoms. Therefore, the positively charged aluminum ion must enter the electrolytic solution.
Since opposite electric charges attract each other, the aluminum ion will diffuse through the electrolytic solution until it reaches the cathode at the other end. Once it comes into contact with the negatively charged cathode, their respective charges cancel and the ion becomes neutral. The aluminum atom then returns to its original solid state, except now it is stuck to the surface of the cathode. If this process continues for an adequate time period, the entire surface of the cathode will become plated with aluminum atoms from the anode.